ARTICLE | doi:10.20944/preprints202011.0586.v1
Subject: Chemistry, Analytical Chemistry Keywords: chemical composition; antioxidant; Citrus; essential oils; Principal Component Analysis.
Online: 23 November 2020 (14:19:03 CET)
Citrus essential oils (EOs) have various bioactivities like antioxidants, with many applications. Antioxidant activities depend on the chemical compositions of the EOs, which are affected by climate, soil, and geographical region. Thus, investigations on chemical compositions and antioxidant activities of Citrus EOs in different countries are valuable. In this study, we distilled EOs from peels of Indonesian-grown Citrus, including C. nobilis, C. limon, C. aurantifolia, C. amblycarpa, and Citrus spp.Chemical compositions of EOs were analyzed using Gas Chromatography-Mass Spectrometer (GC-MS), whereas the antioxidant activities were determined by employing 2,2-diphenyl-2-picrylhydrazyl (DPPH) method. Furthermore, principal component analysis (PCA) was applied to elucidate the main contributing compounds for antioxidant activity. The results show that all EOs possess unique chemical characteristics, with limonene as the majority constituent. For antioxidant activities, C. limon and C. amblycarpa EOs are the two strongest, IC50 values below 7.00 μL/mL. PCA approach suggests that -terpinene mainly contributes to the high antioxidant activities of C. limon and C. amblycarpa. Moreover, o-cymene, thymol, p-cymene, and α-pharnesene may also be responsible for the antioxidant activity of C. limon EO. These results are valuable information for the applications of Citrus EOs as antioxidant sources.
ARTICLE | doi:10.20944/preprints202011.0579.v1
Subject: Chemistry, Analytical Chemistry Keywords: heterostructures; TiO2 nanosheets; few layers MoS2/TiO2; ex-situ and in-situ approaches; FTIR; Raman; UV-Vis; XRD; HRTEM
Online: 23 November 2020 (10:17:48 CET)
MoS2/TiO2 nanostructures made of MoS2 nanoparticles covering TiO2 nanosheets have been synthesized, either via ex-situ or in-situ approaches. Morphology and structure of MoS2/TiO2 hybrid nanostructures have been investigated and imaged by means of X-ray diffraction (XRD) analysis and high-resolution transmission electron microscopy (HRTEM), while the vibrational and the optical properties have been investigated by Raman, Fourier-transform infrared spectroscopy (FTIR) and UV−visible (UV-Vis) techniques. The different stacking degrees together with the size distribution of the MoS2 nanosheets, decorating the TiO2 nanosheets, have been carefully obtained from HRTEM images. The nature of the surface sites on the main exposed faces of both materials has been detected by means of in-situ FTIR spectra of adsorbed CO probe molecule. The results coming from the ex-situ and in-situ approaches will be compared, by highlighting the role of the synthesis processes in affecting morphology and structure of MoS2 nanosheets, including their curvature, surface defects, and stacking order. Some more, it will be shown that the in-situ approach is affecting the reactivity of the TiO2 nanosheets too, hence in turn affects the MoS2/TiO2 nanosheets interaction.
Fri, 20 November 2020
Subject: Chemistry, Analytical Chemistry Keywords: point-of-care assay; membrane tests; immunochromatography; lateral flow immunoassay; immune response; detection of antibodies; antigen-antibody reactions; mathematical modelling; assay sensitivity; limit of detection
Online: 20 November 2020 (10:50:49 CET)
Determination of the presence in the blood of antibodies specific to the causative agent of a particular disease (serodiagnosis) is an effective approach in medical analytical chemistry. Serodiagnostics performed in the lateral flow immunoassay format (immunochromatography) meet the modern requirements for point-of-care testing and are supported by existing technologies of large-scale diagnostic tests production—thus raising increased attention in a tense epidemiological situation. For traditional lateral flow serodiagnostics formats, a large number of nonspecific immunoglobulins in the sample significantly reduces the degree of detectable binding. To overcome these limitations, an assay based on the formation of immobilized antigen— specific antibody—labeled antigen complexes detection was proposed. However, the requirements for its implementation, providing maximum sensitivity, have not been established. This article describes the mathematical model for the above assay. The influence of the ratio of reagent concentrations on the analysis results is considered. It is noted that the formation of specific antibody complexes with several labeled antigens is the main limiting factor in reducing the detection limit, and methods are proposed to minimize this factor. Recommendations for the choice of the assay conditions, following from the analysis of the model, are confirmed experimentally.
Thu, 19 November 2020
ARTICLE | doi:10.20944/preprints202011.0524.v1
Subject: Chemistry, Analytical Chemistry Keywords: zinc finger; protein; MM/GBSA; DNA binding; molecular dynamics; mutation; linkers
Online: 19 November 2020 (21:21:37 CET)
Zinc finger proteins (ZFP) play important roles in cellular processes. The DNA binding region of ZFP consists of 3 zinc finger DNA binding domains connected by amino acid linkers, the sequence TGQKP connects ZF1 and ZF2, and TGEKP connects ZF2 with ZF3. Linkers act to tune the zinc finger protein in the right position to bind its DNA target, the type of amino acid residues and length of linkers reflect on ZF1-ZF2-ZF3 interactions and contribute to the search and recognition process of ZF protein to its DNA target. Linker mutations and the affinity of the resulting mutants to specific and nonspecific DNA targets were studied by MD simulations and MM_GB(PB)SA. The affinity of mutants to DNA varied with type and position of amino acid residue. Mutation of K in TGQKP resulted in loss in affinity due to the loss of positive K interaction with phosphates, mutation of G showed loss in affinity to DNA, WT protein and all linker mutants showed loss in affinity to a nonspecific DNA target, this finding confirms previous reports which interpreted this loss in affinity as due to ZF1 having an anchoring role, and ZF3 playing an explorer role in the binding mechanism. The change in ZFP-DNA affinity with linker mutations is discussed in view of protein structure and role of linker residues in binding.
ARTICLE | doi:10.20944/preprints202011.0517.v1
Subject: Chemistry, Analytical Chemistry Keywords: titanium dioxide; oxidation; photocatalysis; VOCs mineralization; Langmuir-Hinshelwood
Online: 19 November 2020 (15:20:44 CET)
A jointed experimental and theoretical investigation pointing out new insights about the microscopic mechanism of the VOCs (volatile organic compounds) photocatalytic elimination by TiO2 has been done. Methane, hexane, isooctane, acetone and methanol have been photomineralized in a batch reactor. Values of K (adsorption constant on TiO2) and k (mineralization rate constant) of the five VOCs (treating the kinetic data through a Langmuir- Hinshelwood approach) have been determined. Recorded K and k values and performed theoretical calculations allowed us to suggest the involvement of an electron transfer step between the VOC and the hole, TiO2(h+), as the rate determining one.
Wed, 18 November 2020
ARTICLE | doi:10.20944/preprints202011.0479.v1
Subject: Chemistry, Analytical Chemistry Keywords: Noble Gas Anions; Noble Gas Chemistry; Electron Density; Stability of Noble-Gas Containing Molecules
Online: 18 November 2020 (14:01:51 CET)
The fluorine-less noble-gas containing anions OBONgO- and OCNNgO-have been studied by correlated electronic structure calculation and density functional theory. The obtained energetics indicates that for Ng = Kr and Xe, these anions should be kinetically stable at low temperature. The molecular structures and electron density distribution suggests that these anions are stabilized by ion-induced dipole interactions with charges concentrated on the electronegative OBO and OCN groups. The current study shows that in additional to the fluoride ion, polyatomic groups with strong electronic affinities can also form stable noble-gas containing anions of the type X-...NgO.
Mon, 16 November 2020
ARTICLE | doi:10.20944/preprints202011.0440.v1
Subject: Chemistry, Analytical Chemistry Keywords: Au nanoparticles; nanocarriers; methotrexate; anticancer drug; chemotherapeutics; controlled release
Online: 16 November 2020 (17:38:03 CET)
In the present study the synthesis of gold nanoparticles (AuNPs) loaded with methotrexate (MTX) has been carried out in order to obtain controlled size and monodispersed nanocarriers, around 20nm. Characterization study shows metallic AuNPs with MTX polydispersed on the surface. MTX is linked by a replacement of citrate by the MTX carboxyl group. The drug release profiles showed faster MTX release when it is conjugated, which leads to the best control of plasma concentration. Also, the enhanced release observed at pH 5 could take advantage of the pH gradients that exist in tumor microenvironments to achieve high local drug concentrations. AuNPs-MTX conjugates were tested by flow cytometry against lung (A-549) and colon (HTC-116) cancer cell lines. Results for A-549 showed a lighter dose-response effect than for colon cancer ones. This could be related to the presence of folate receptors in line HTC-116 on the contrary than line A-549, supporting the specific uptake of folate-conjugated AuNPs-MTX by folate receptor positive tumor cells. Conjugates exhibited considerably higher cytotoxic effects compared with the effects of equal doses of free MTX. Anexin V-PI test sustain as cell death mechanism apoptosis, which is normally disabled in cancer cells.
Fri, 13 November 2020
Subject: Chemistry, Analytical Chemistry Keywords: innovative grape varieties; organic wine; biogenic amine; polyphenol
Online: 13 November 2020 (13:58:14 CET)
Society considers wine as a special product among food and beverages because of its high gastronomical value and its positively distinctive quality. In recent years, philosophies of the agricultural techniques and development of the oenological technology have been focused on the reduction of wasteful, "polluting" elements, and trends are moving towards an environmental friendly approach. Due to the stricter regulations and rules (with the limited amount and selection of the permitted chemicals) resistant, also known as interspecific or innovative grape varieties can be the ideal basic materials of alternative cultivation technologies. In terms of variety selection, innovative varieties can be equivalent to international varieties, although organically their quality could not compete with them. These grapes are more resistant to various fungal diseases and infections than international varieties. Well-founded analytical and organoleptic results have to provide the scientific background of resistant varieties, as these cultivars with the environmental friendly cultivation techniques, could be the raw material of the future.
ARTICLE | doi:10.20944/preprints202011.0371.v1
Subject: Chemistry, Analytical Chemistry Keywords: membrane transport; A327H+Cl- ionic liquid; gold; hydrochloric acid; nanoparticles.
Online: 13 November 2020 (10:57:44 CET)
By the use of the tertiary amine A327 and 1 M HCl solution as precursors, the ionic liquid A327H+Cl- was generated and used to investigate its performance in the transport of Au(III) form hydrochloric acid medium. The influence of the stirring speed (600-1800 min-1), ionic liquid concentration (1.25-50% v/v) in the membrane phase and gold concentration (0.01-0.15 g/L) in the feed phase on metal transport have been investigated. An equation which included both equilibrium and kinetics parameters was derived, and the membrane diffusional resistance (Δm) and feed phase diffusional resistance (Δf) was estimated as 9.5x106 s/cm and 307 s/cm, respectively. At carrier concentrations in the 5-50% v/v range and gold concentrations in the 0.01-0.15 g/L range, metal transport is controlled by diffusion of metal species through the feed boundary layer, whereas at the lowest carrier concentrations, membrane diffusion is predominant. From the receiving solutions, gold can be recovered as gold nanoparticles.
ARTICLE | doi:10.20944/preprints202011.0363.v1
Subject: Chemistry, Analytical Chemistry Keywords: cannabinoid receptor 1; synthetic cannabinoids; quantitative structure-activity relationship; multiple linear regression; partial least squares regression; dependence and abuse potential
Online: 13 November 2020 (07:19:36 CET)
In recent years, there have been frequent reports on the adverse effects of synthetic cannabinoid (SC) abuse. SCs cause psychoactive effects, similar to those caused by marijuana, by binding and activating cannabinoid receptor 1 (CB1R) in the central nervous system. The aim of this study was to establish a reliable quantitative structure-activity relationship (QSAR) model to correlate the structures and physicochemical properties of various SCs with their CB1R-binding affinities. We prepared 15 SCs and their derivatives (tetrahydrocannabinol [THC], naphthoylindoles, and cyclohexylphenols) and determined their binding affinity to CB1R, which is known as a dependence-related target. We calculated the molecular descriptors for dataset compounds using an R/CDK (R package integrated with CDK, version 3.5.0) toolkit to build QSAR regression models. These models were established and statistical evaluations were performed using the mlr and plsr packages in R software. The most reliable QSAR model was obtained from the partial least squares regression method via external validation. This model can be applied in vivo to predict the addictive properties of illicit new SCs. Using a limited number of dataset compounds and our own experimental activity data, we built a QSAR model for SCs with good predictability. This QSAR modeling approach provides a novel strategy for establishing an efficient tool to predict the abuse potential of various SCs and to control their illicit use.
Tue, 10 November 2020
ARTICLE | doi:10.20944/preprints202011.0305.v1
Subject: Chemistry, Analytical Chemistry Keywords: Leucophyllum frutescens; Total Phenolic Contents (TPC); Total Flavonoid Content (TFC); Total Antioxidant Activity (TAA); DPPH; CUPRAC; FRAP; gas chromatography-mass spectrometry (GC-MS)
Online: 10 November 2020 (12:00:06 CET)
The four solvent extractives obtained from aerial parts of Leucophyllum frutescens were evaluated for their Total Antioxidant Activity (TAA) by ammonium molybdate method, scavenging potential by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Trolox-Equivalent Antioxidant Capacity (TEAC) assays, metal-reducing potential by Cupric Reducing Antioxidant Capacity (CUPRAC) and Ferric Reducing Antioxidant Power (FRAP) assays, Total Phenolic Content (TPC), Total Flavonoid Content (TFC) and their biological activities. The study concluded that BULE exhibited total antioxidant activity (226.235±1.222 mg AA.Eq.gm-1 DE±S.D) by molybdate method, CHLE exhibited more scavenging potential (DPPH 209.589±8.500 mg trolox Eq.gm-1 DE±S.D and TEAC 210.166±7.954 mg trolox Eq.gm-1 DE±S.D) and reducing potential (CUPRAC 646.889±16.889 mg trolox Eq.gm-1 DE±S.D & FRAP 472.981±15.625 mg trolox Eq.gm-1 DE±S.D). Phytochemical quantification concluded high TPC by BULE (189.369±1.393 mg GA.Eq.gm-1 DE±S.D) and high TFC by CHLE (232.458±1.589 mg Qu.Eq.gm-1 DE±S.D). Strong inhibition of α-glucosidase and urease enzymes was observed by HELE (IC50 0.3321±0.007 mg.ml-1±SD) and BULE (IC50 4.09±0.357 mg.ml-1±SD) extractives, respectively. The hemolytic effect shown by hexane extract (HELE) was higher with HA50 25.545±0.927 ug.ml-1±SD whereas methanol (MELE), chloroform (CHLE), and butanol (BULE) exhibited hemolytic effects at higher concentration with HA50 400.067±1.364, 321.394±1.332, and 332.957±0.465 µg.ml-1±SD, respectively. GC-MS profiling of HELE of L. frutescens was performed for qualitative analysis. The principal phytochemicals tentatively identified by GC-MS analysis of HELE accounts for fatty acids (60.221%), lignans (17.687%), ketones (3.358%), phenols (2.584%), sesquiterpenes (1.265%), and aldehydes (0.345%).
REVIEW | doi:10.20944/preprints202011.0301.v1
Subject: Chemistry, Analytical Chemistry Keywords: Ruthenium; Heterogeneous; Levulinic acid; hydrogenation; γ-valerolactone.
Online: 10 November 2020 (10:36:07 CET)
Catalytic hydrogenation of a biomass-derived molecule, levulinic acid (LA) to γ-valerolactone (GVL) has been getting a lot of attention from researchers across the globe recently. This is because GVL has been identified as one of the potential molecules for the replacement of fossil fuels. For instance, GVL can be catalytically converted into liquid alkenes in the molecular weight range close to that found in transportation fuels via a process that does not require an external hydrogen source. Noble and non-noble metals have been used as catalysts for the selective hydrogenation of LA to GVL. Of these, Ru has been reported to be the most active metal for this reaction. The type of metal supports and solvents has been proved to affect the activity, selectivity, and yields of GVL. Water has been identified as a potential, effective “green” solvent for the hydrogenation of LA to GVL. The use of different sources of H2 other than molecular hydrogen (such as formic acid) has also been explored. In a few instances, the product, GVL, is hydrogenated further to other useful products such as 1,4-pentanediol (PD) and methyl tetrahydrofuran (MTHF). This review selectively focuses on the potential of immobilized Ru catalysts as a potential superior catalyst for selective hydrogenation of LA to GVL.
REVIEW | doi:10.20944/preprints202011.0295.v1
Subject: Chemistry, Analytical Chemistry Keywords: dendritic polymers; ceramic compounds; biomimetic; nanomaterials; dendrimers; hyperbranched polymers; silica composites; hybrid materials
Online: 10 November 2020 (09:22:43 CET)
As the field of nanoscience is rapidly evolving, interest for novel, upgraded nanomaterials with combinatory features is also inevitably increasing. Hybrid composites, offer simple, budget-conscious and environmental-friendly solutions that can cater multiple needs at the same time and be applicable in many nanotechnology-related and interdisciplinary studies. The physicochemical idiocrasies of dendritic polymers have inspired their implementation as sorbents, active ingredient carriers and templates for complex composites. Ceramics are distinguished for their mechanical superiority and absorption potential that render them ideal substrates for separation and catalysis technologies. The integration of dendritic compounds to these inorganic hosts can be achieved through chemical attachment of the organic moiety onto functionalized surfaces, impregnation and absorption inside the pores, conventional sol-gel reactions or via biomimetic mediation of dendritic matrices, inducing the formation of usually spherical hybrid nanoparticles. Alternatively, dendritic polymers can propagate from ceramic scaffolds. All these variants are covered in detail. Optimization techniques as well as established and prospected applications are also presented.
Sun, 8 November 2020
ARTICLE | doi:10.20944/preprints202011.0258.v1
Subject: Chemistry, Analytical Chemistry Keywords: air-acetic acid system; gas holdup; differential pressure transmitter; ERT; optical fiber probe
Online: 8 November 2020 (14:50:39 CET)
The hydrodynamic behavior of the air-acetic acid system in a bubble column is studied using a differential pressure transmitter, double probe optical fiber probe, and the electrical resistance tomography (ERT) technique. The superficial gas velocity ranges from 0.016 to 0.094 m/s under ambient temperature and pressure. The influences of viscosity and surface tension on gas holdup, bubble rising velocity, and bubble chord distribution in the column are discussed with different mass fractions of an acetic acid solution. The results show that as the mass fraction of acetic acid increases, the surface tension of the liquid phase decreases, and the viscosity first increases and then decreases. This causes the gas holdup in the column to first increase and then decrease, and reaches the maximum value at an acetic acid mass fraction of 55% to 60%. The rising velocity of the bubbles in the column is high in the central region and has a low-value distribution near the wall. The bubble chord length distribution is concentrated, and the distribution of the bubble chord length in the column becomes narrow with any decrease in surface tension. Studying the hydrodynamic behavior of a bubble column with the air-acid system is of great significance considering the absence of data on air-organic acid systems.
Fri, 6 November 2020
ARTICLE | doi:10.20944/preprints202011.0226.v1
Subject: Chemistry, Analytical Chemistry Keywords: activated carbon; hydrothermal carbonization (HTC); exergy analysis; thermoeconomic analysis; circular economy.
Online: 6 November 2020 (08:07:04 CET)
An activated carbon manufacturing process using winemaking waste is analyzed and designed at industrial scale. Starting from experimental research, the chemical transformations and thermodynamics during pruning wood conversion are studied as a basis for plant design. In this way, mass and energy balances of hydrothermal carbonization and physical activation are fulfilled and a thermoeconomic methodology is applied to develop an energy-integrated plant. To achieve this target, a network of heat exchangers is allocated to minimize heat consumption and supply hot domestic water, while a cogeneration cycle is designed to provide electricity and satisfy the remaining heat demand. Furthermore, a sensitivity analysis is carried out to determine the influence of the production scale and other operation parameters, such as annual workload, service life, and capital and feedstock costs, on the economic viability of the plant. The energy balance of the plant indicates that the energy integration design manages to provide 48.9% of the overall process energy demand by crossing hot and cold streams and recovering heat from residual flue gas. On the other hand, the exergy cost analysis identifies the combustion of pruning wood used to provide heat demands as the main source of exergy destruction, confirming the suitability of integration to improve the thermodynamic performance. Including activated carbon production, electricity, and hot domestic water, the exergy efficiency of the plant stands at 11.5%.
Wed, 4 November 2020
ARTICLE | doi:10.20944/preprints202011.0195.v1
Subject: Chemistry, Analytical Chemistry Keywords: codfish; enzymatic hydrolysis; proteomics; bioinformatic prediction; emulsifying properties; antioxidative activity; bioactive peptides
Online: 4 November 2020 (12:44:08 CET)
Protein hydrolysates show great promise as bioactive food and feed ingredient and for valorization of side-streams from e.g. the fish processing industry. This study characterizes bulk emulsifying, foaming, and in vitro antioxidative properties of hydrolysates derived from cod frame by application of Alcalase and Neutrase, individually and sequentially as well as the influence of heat-treatment prior to hydrolysis. We present a novel approach that utilizes proteomics data for calculation of weighted mean peptide properties (length, molecular weight, and charge) and peptide-level abundance estimation. Using subsequent bioinformatic prediction of biofunctional properties to describe observed bulk properties, we are able to provide an in-depth hydrolysate characterization not previously seen. All hydrolysates displayed comparable or higher emulsifying activity and stability than sodium caseinate. Heat-treatment significantly increased stability but showed a negative effect on the activity and degree of hydrolysis. Combining peptide abundance with predicted emulsifying activity, we were able to identify several peptides that are likely linked to the observed differences in bulk emulsifying properties. In general, decreased hydrolysis resulted in significantly higher chelating activity, while the opposite was observed for radical scavenging activity. The study highlights the prospects of applying proteomics and bioinformatics for hydrolysate characterization and in food protein science.
ARTICLE | doi:10.20944/preprints202011.0194.v1
Subject: Chemistry, Analytical Chemistry Keywords: hydrogel; e-beam cross-linking; swelling; ibuprofen; network parameters
Online: 4 November 2020 (12:41:17 CET)
We report on the successful preparation of wet dressings hydrogels based on Chitosan-Poly(N-Vinyl-Pyrrolidone)-Poly(ethylene glycol)-Poly(acrylic acid) and Poly(ethylene oxide) by e-beam cross-linking in weakly acidic media, to be used for rapid healing and pain release of infected skin wounds. The structure and compositions of hydrogels investigated according to sol-gel and swelling studies, network parameters, as well as FTIR and XPS analyses showed the efficient interaction of the hydrogel components upon irradiation, maintaining the bonding environment while the cross-linking degree increasing with the irradiation dose and the formation of a structure with the mesh size in the range 11-67 nm. Hydrogels with gel fraction above 85% and the best-swelling properties in different pH solutions were obtained for hydrogels produced with 15 kGy. The hydrogels are stable in the simulated physiological condition of an infected wound and show appropriate moisture retention capability and the water vapor transmission rate up to 272.67 g m-2 day-1, to ensure fast healing. The hydrogels proved to have a significant loading capacity of ibuprofen (IBU), being able to incorporate a therapeutic dose for the treatment of severe pains. Simultaneously, IBU was released up to 25% in the first 2h, having a release maximum after 8h.
ARTICLE | doi:10.20944/preprints202011.0146.v2
Subject: Chemistry, Analytical Chemistry Keywords: Ferric Uptake Regulation; Fur, Iron(II), Molecular dynamics; DNA; protein
Online: 4 November 2020 (10:13:32 CET)
Ferric uptake regulation protein is a repressor protein which binds an AT rich region of DNA (the iron box). Fur binds as a dimer in a helix turn helix mode and it is activated by iron(II) and other transition metal ions at elevated concentrations. Each transition metal ion induces certain conformational changes to aid the Fur binding, both the N-terminal and C-terminal domains take part in binding to DNA in addition to His 88 and His 86. The process is discussed in view of experimental reports. Fe(II), Mn(II) and Co(II) activate Fur to bind DNA but Zinc plays a structural role and does not activate Fur to bind DNA.
Tue, 3 November 2020
ARTICLE | doi:10.20944/preprints202011.0146.v1
Subject: Chemistry, Analytical Chemistry Keywords: Ferric Uptake Regulation; Fur, Iron(II), Molecular dynamics; DNA; protein
Online: 3 November 2020 (12:49:52 CET)
Ferric uptake regulation protein is a repressor protein which binds an AT rich region of DNA (the iron box). Fur binds as a dimer in a helix turn helix mode and it is activated by iron(II) and other transition metal ions at elevated concentrations. Each transition metal ion induces certain conformational changes to aid the Fur binding, both the N-terminal and C-terminal domains take part in binding to DNA in addition to His 88 and His 86. The process is discussed in view of experimental reports. Fe(II), Mn(II) and Co(II) activate Fur to bind DNA but Zinc plays a structural role and does not activate Fur to bind DNA.
Mon, 2 November 2020
ARTICLE | doi:10.20944/preprints202011.0047.v1
Subject: Chemistry, Analytical Chemistry Keywords: Photodynamic Therapy; Charge Transfer; Electronically Excited States; Anthraquinone; DNA; Molecular Dynamics; TD-DFT; Transition-Density Analysis
Online: 2 November 2020 (14:15:09 CET)
The design of more efficient photosensitizers is a matter of great importance in the field of cancer treatment by means of photodynamic therapy. One of the main processes involved in the activation of apoptosis in cancer cells is the oxidative stress on DNA once a photosensitizer is excited by light. As a consequence, it is a matter of great relevance to investigate in detail the binding modes of the chromophore with DNA, and the nature of the electronically excited states that participate in the induction of DNA damage, for example, charge-transfer states. In this work, we investigate the electronic structure of the anthraquinone photosensitizer intercalated into a double-stranded poly(dG-dC) decamer model of DNA. First, the different geometric configurations are analyzed by means of classical molecular dynamics simulations. Then, the excited states for the most relevant poses of anthraquinone inside the binding pocket are computed by an electrostatic-embedding quantum mechanics/molecular mechanics approach, where anthraquinone and one of the nearby guanine residues are described quantum mechanically to take into account intermolecular charge-transfer states. The excited states are characterized as monomer, exciton, excimer and charge-transfer states based on the analysis of the transition density matrix, and each of these contributions to the total density of states and absorption spectrum is discussed in terms of the stacking interactions. These results are relevant as they represent the footing for future studies on the reactivity of anthraquinone derivatives with DNA and give insights on possible geometrical configurations that potentially favor the oxidative stress of DNA.
ARTICLE | doi:10.20944/preprints202011.0027.v1
Subject: Chemistry, Analytical Chemistry Keywords: Brugada syndrome; peptide nucleic acid-PNA, porous silicon; graphene oxide; optical biosensor; hybrid device
Online: 2 November 2020 (11:12:24 CET)
Peptide nucleic acid (PNA) is a synthetic DNA mimic that outperforms the properties of traditional oligonucleotides (ONs). On account of its outstanding features, such as remarkable binding affinity towards complementary DNA or RNA as well as high thermal and chemical stability, PNA has been proposed as a valuable alternative to the ON probe in gene-sensor design. In this study, a hybrid transducer made-up of graphene oxide (GO) nano-sheets covalently grafted onto a porous silicon (PSi) matrix has been investigated for the early detection of a genetic cardiac disorder, the Brugada syndrome (BS). A functionalization strategy towards the realization of a potential PNA-based device is described. A peptide nucleic acid (PNA), able to detect the SCN5A associated with the BS has been properly synthesized and used as a bioprobe for the realization of a proof-of-concept label-free optical PNA-biosensor. PSi reflectance and GO photoluminescence (PL) signals were simultaneously exploited for the monitoring of the device functionalization and response.
Fri, 30 October 2020
ARTICLE | doi:10.20944/preprints202010.0627.v1
Subject: Chemistry, Analytical Chemistry Keywords: activated carbon; winemaking waste; wastewater; Cr(VI) removal; adsorption process; Cr(VI) reduction
Online: 30 October 2020 (08:28:29 CET)
A winemaking waste was used as a precursor of activated carbon used in hazardous Cr(VI) removal from solutions. The preparation process consisted of a hydrothermal process, and a chemical activation, of the resulting product, with KOH. The adsorption results showed that the adsorption of Cr(VI) on the obtained activated carbon is strongly dependent on the stirring speed applied to the carbon/solution mixture, pH of the solution, and temperature. The equilibrium isotherm was well fitted to the Langmuir type-II equation, whereas the kinetic can be described by the pseudo-second-order kinetic model. Thermodynamic studies revealed that Cr(VI) adsorption was an exothermic and spontaneous process. Finally, desorption experiments showed that Cr(VI) was effectively desorbed using hydrazine sulfate solutions, and at the same time, the element was reduced to the less hazardous Cr(III) oxidation state.
Wed, 28 October 2020
ARTICLE | doi:10.20944/preprints202010.0576.v1
Subject: Chemistry, Analytical Chemistry Keywords: Antimalarial; Erythrina fusca; Phaseolin; Molecular docking; Phytochemical analysis
Online: 28 October 2020 (09:59:54 CET)
For centuries medicinal plants have been traditionally used for prophylaxis and ailment of diseases. Nowadays it’s easy to isolate, purify, and characterize bioactive compounds with high efficacy. To investigate the medicinal especially antimalarial property of traditionally used plants, a number of Erythrina spp have been reviewed systematically where Erythrina fusca has been selected for further analysis. Phytochemical investigation included chromatographic separation and purification of compounds followed by characterization using NMR. In-vitro antimalarial drug sensitivity ELISA was carried out against chloroquine (CQ) sensitive 3D7 and resistant Dd2 strains. Additional biological tests such as central and peripheral analgesic, antioxidant, anti-diarrheal, hypoglycemic, thrombolytic, and membrane stabilization activities were also investigated. Molecular docking was performed using the isolated compounds against clinically important 14 Plasmodium falciparum proteins. For the first time, Phaseolin, Phytol, β-amyrin, Lupeol, and Stigmasterol are reported here and extracts showed significant antimalarial activity against 3D7 and Dd2 strains (IC50 4.94-22 µg/mL). Potent central analgesic, antioxidant and anti-diarrheal activities (p<0.05) and mild thrombolytic and membrane stabilization properties were also observed. Molecular docking of Phaseolin bolsters its potential as a new antimalarial drug candidate. This study projects significant medicinal values and necessitates further investigations to reveal its potential as a novel source of therapeutics.
Mon, 26 October 2020
ARTICLE | doi:10.20944/preprints202010.0506.v1
Subject: Chemistry, Analytical Chemistry Keywords: Paper-based microfluidic device; colorimetric; multiple detection; smartphone application
Online: 26 October 2020 (08:56:58 CET)
Paper-based microfluidic analysis devices (μPADs) have attracted attention as a cost-effective platform for point-of-care testing (POCT), food safety, and environmental monitoring. Recently, three-dimensional (3D)-μPADs have been developed to improve the performance of μPADs. For accurate diagnosis of diseases, however, 3D-μPADs need to be developed to simultaneously detect multiple biomarkers. Here, we report a 3D-μPADs platform for the detection of multiple biomarkers that can be analyzed and diagnosed with a smartphone. The 3D-μPADs were fabricated using a 3D digital light processing printer and consisted of a sample reservoir (300 µL) connected to 24 detection zones (of 4 mm in diameter) through 8 microchannels (of 2 mm in width). With the smartphone application, eight different biomarkers related to various diseases were detectable in concentrations ranging from normal to abnormal conditions: glucose (0–20 mmol/L), cholesterol (0–10 mmol/L), albumin (0–7 g/dL), alkaline phosphatase (0–800 U/L), creatinine (0–500 µmol/L), aspartate aminotransferase (0–800 U/L), alanine aminotransferase (0–1000 U/L), and urea nitrogen (0–7.2 mmol/L). These results suggest that 3D-µPADs can be used as a POCT platform for simultaneous detection of multiple biomarkers.
Fri, 23 October 2020
ARTICLE | doi:10.20944/preprints202010.0486.v1
Subject: Chemistry, Analytical Chemistry Keywords: COVID-19; carnosine; angiotensin-converting enzyme 2 (ACE2); practitioner; molecular docking; modeling
Online: 23 October 2020 (10:44:07 CEST)
Aims: Angiotensin-converting enzyme 2 (ACE2) plays an important role in the entry of coronaviruses into host cells. This paper described how carnosine, a naturally occurring supplement, can be an effective drug candidate for coronavirus disease (COVID-19) on the basis of molecular docking and modeling to host ACE2 co-crystallized with COVID-19 spike protein. Methods: First, the starting point was ACE2 inhibitors and their structure-activity relationship (SAR). Next, chemical similarity (or diversity) and PubMed searches made it possible to repurpose and assess approved or experimental drugs for COVID-19. In parallel, at all stages, authors performed bioactivity scoring to assess potential repurposed inhibitors at ACE2. Finally, investigators performed molecular docking and modeling of the identified drug candidate to host ACE2 co-crystallized with COVID-19 spike protein. Results: Carnosine emerged as the best known drug candidate to match ACE2 inhibitor structure. Preliminary docking was more optimal to ACE2 than the known typical angiotensin-converting enzyme 1 (ACE1) inhibitor (enalapril) and quite comparable to known or presumed ACE2 inhibitors. Viral spike protein elements binding to ACE2 were retained in the best carnosine pose in SwissDock at 1.75 Angstroms. Out of the three main areas of attachment expected to the co-crystallized protein structure, carnosine bind with higher affinity to two compared to the known ACE2 active site. LibDock score was 92.40 for site 3, 90.88 for site 1, and inside the active site 85.49. Conclusion: Carnosine has promising inhibitory interactions with host ACE2 co-crystallized with COVID-19 spike protein and hence could offer potential mitigating effect against current COVID-19 pandemic.
Thu, 22 October 2020
ARTICLE | doi:10.20944/preprints202010.0448.v1
Subject: Chemistry, Analytical Chemistry Keywords: Cellulose; agricultural waste; bioadsorbent; rare earth; terbium adsorption-desorption
Online: 22 October 2020 (09:00:24 CEST)
Preparation of a low-cost cellulose-based bioadsorbent from the cellulosic material extracted from the rose stems (CRS) was carried out; rose stems were considered agricultural wastes. After the required pretreatment of this waste, and its further treatment with an acidic mixture of acetic and nitric acids, the CRS product was yielded. The resulting bioadsorbent was characterized by several techniques, such as X-ray diffraction, which revealed diffraction maxima related to cellulose structure, whose calculated crystallinity index (CrI) was 75 %. In addition, Fourier Transform Infrared spectroscopy (FTIR), 13C Nuclear Magnetic Resonance (NMR), and X-ray Photoelectron Spectroscopy (XPS) showed signs of acetylation of the sample, also, the thermal properties of the solid was evaluated through Thermogravimetric Analysis (TGA). Scanning Electron Microscopy (SEM) showed cellulose fibers before and after the adsorption process, some particles with not regular shapes were also observed. The CRS bioadsorbent was used in the effective adsorption of valuable Tb(III) from aqueous solution. The adsorption data resulted in a better fit to the Freundlich isotherm, and pseudo-second-order kinetic models; however, chemisorption had not been ruled out. Finally, desorption experiments revealed a recovery of terbium ions with an efficiency of 97 % from terbium-loaded bioadsorbent.
Wed, 21 October 2020
ARTICLE | doi:10.20944/preprints202010.0430.v1
Online: 21 October 2020 (10:45:49 CEST)
Literature reported the insulin is an important for the humans and it is secreted in the pancreas and controls, regulates the glucose level. It also controls the mechanism and growth. On decreasing the amount of insulin can caused diabetes, several cancers and other disease. Therefore, there is a need to find promising candidates can binds with insulin and stabilize them. Organic compounds containing hetero atoms have lots of biological potency in different area, therefore, researchers are designing new biological potent compounds. Further, insilico studies attracted the researchers in last one decade mainly to get the drug in less time with a clear strategy. In the present work, authors have designed two types of conjugates, xanthenes with trizole as well benzisoxazole and study their interaction with the insulin using computational methods. The library of compounds was screened through molecules docking in terms of binding energy between the designed compound and the active site of the receptor. Further, their ADME properties are investigated. CMPD19 showed best binding affinity with the insulin and may be considered as oral drug based on the bioactive scores.
Tue, 20 October 2020
ARTICLE | doi:10.20944/preprints202010.0405.v1
Subject: Chemistry, Analytical Chemistry Keywords: cap - pair effect; electrochemistry; electroreduction of Bi(III); active complexes; catalytic activity
Online: 20 October 2020 (08:36:05 CEST)
The paper discusses the electroreduction of Bi(III) ions in the aspect of expanding the ”cap – pair” effect. The ”cap – pair” rule is associated with the acceleration of the electrode’s processes by organic substances. The interpretation of the ”cap – pair” effect mechanism was expanded to include the effect of supporting electrolyte concentration on the acceleration process and the type of electrochemical active as well as used protonated organic substances. It has also been shown that the phenomena occurring at the electrode/solution interface can influence a change in the dynamics of the electrode’s process according to the ”cap – pair” rule.
Mon, 19 October 2020
Subject: Chemistry, Analytical Chemistry Keywords: Cow milk; Enzymatic hydrolysis; Allergic protein; Antigenicity
Online: 19 October 2020 (11:04:35 CEST)
In this paper, the effects of different food-grade enzymes on the antigenicity of casein (CN), β- lactoglobulin (β-LG) and ɑ-lactalbumin (ɑ-LA) in natural cow milk were studied. The degree of hydrolysis (DH), SDS-PAGE and molecular mas (MW) distribution of cow milk (CM) hydrolysates was assessed. Additionally, the residual antigenicity of CM hydrolysates was evaluated by using ELISA and western blotting with anti-CN, anti-β-LG and anti-ɑ-LA rabbit polyclonal antibody. The results showed that Alcalase and Protamex hydrolysis could efficiently reduce the antigenicity of CN, β-LG, ɑ-LA, showed a higher DH and the loss of density of CM proteins, as indicated by SDS-PAGE. The increasing of the low MW (<3 kDa) in CM hydrolysates was also presented. It was also found that Protamex, Alcalase could be more efficiently hydrolyzed major allergenic of CM than other enzymes for the development of hypoallergenic cow milk. Our research will lay a theoretical foundation for the study of hypoallergenic cow milk.
Fri, 16 October 2020
Subject: Chemistry, Analytical Chemistry Keywords: Verteporfin; Photosensitizer; Photo Dynamic Therapy; PDT; Photofragments; Photofragmentation channels; Mass Spectrometry; Laser Spectroscopy; Photolysis
Online: 16 October 2020 (14:39:28 CEST)
Verteporfin, a free base benzoporphyrin derivative monoacid ring A, is a photosensitizing drug for photodynamic therapy (PDT) used in the treatment of the wet form of macular degeneration and activated by red light of 689 nm. Here, we present the first direct study of its photofragmentation channels in the gas-phase, conducted using a laser interfaced mass spectrometer across a broad photoexcitation range from 250-790 nm. The photofragmentation channels are compared with the collision-induced dissociation (CID) products revealing similar dissociation pathways characterized by the loss of the carboxyl and ester groups. Complementary solution-phase photolysis experiments indicate that photobleaching occurs in verteporfin in acetonitrile; a notable conclusion, as photoinduced activity in Verteporfin was not thought to occur in homogenous solvent conditions. These results provide unique new information on the thermal break-down products and photoproducts of this light-triggered drug.
Mon, 12 October 2020
Subject: Chemistry, Analytical Chemistry Keywords: polymerization kinetics; photoinitiator; monomer conversion profile; synergetic effects
Online: 12 October 2020 (10:41:24 CEST)
The synergetic features of a three-component photoinitiating systems (A/B/C) based on the measured data and proposed mechanism of Liu et al (Polymers, 2020, 12(6), 1394) are analyzed. The co-initiators/additives B and C have dual functions of : (i) regeneration of photoinitiator A and (ii) generation of extra radicals. The synergic effects lead to higher conversion of free radical polymerization (FRP) and cationic polymerization (CP). The key factors and rate constants influencing the conversion efficacy are explored by analytic formulas. Enhancing strategies for various photopolymerization systems are summarized including one component (or monomer) and one-wavelength, two-component and one, two and three-wavelength, and three-component, one-wavelength system. The synergetic effects for higher monomer conversion can be achieved by co-initiators for extra radicals and multiple wavelengths for reduced oxygen-inhibition. Co-initiator B, however, might also reduces the CP radical produced by initiator C. The conversion rate of FRP is proportional to the square root of the light intensity (I), absorption (b) and the initiator initial concentratios (A0, B0, C0), whereas CP is proportional to the linear power of a parameter defined as P=bIA0C0, a stronger dependence than FRP. The CP conversion is governed by a steady-state value proportional to P, and a rate fucntion defining the depletion rate of [A][C], or the increasing rate of the conversion profile. The measured results of Liu et al (Polymers, 2020, 12(6), 1394) are well analyzed and matching the predicted features of our modeling. The specific systems analyzed are: benzophenone derivatives (A) ethyl 4-(dimethylamino)benzoate (B), and (4-tert-butylphenyl)iodonium hexafluorophosphate (C) under a UV (365 nm) LED irradiation; and monomers of trimethylolpropane triacrylate (TMPTA, for FRP) and (3,4- epoxycyclohexane)methyl 3,4-epoxycyclohexylcarboxylate (EPOX, for CP).
Subject: Chemistry, Analytical Chemistry Keywords: metallacycloalkynes; metallapentalynes; synthesis, reactivities
Online: 12 October 2020 (07:54:57 CEST)
Due to the linear property around an acetylenic carbon, the introduction of such an atom to a small cycle would result in high ring strain. Currently, the smallest isolated rings are five-membered, including metallacycloalkynes and metallapentalynes. Both types contain at least one unusual small bond angle around the acetylenic carbon, thus exhibiting abnormal reactivities. This feature article gives a comprehensive overview on these two kind complexes. The synthesis and reactivities are extensively described, the source of stability is presented, and the future prospect is discussed. The article aims to provide a better development for the chemical diversity of five-membered metallacycloalkynes and metallapentalynes.
Fri, 9 October 2020
ARTICLE | doi:10.20944/preprints202010.0189.v1
Subject: Chemistry, Analytical Chemistry Keywords: antioxidants for the treatment of ROS; new ester of eugenol; cosmetic formulations with clove water; skin penetration; Franz cell
Online: 9 October 2020 (08:59:05 CEST)
The main focus of this work is to extend the knowledge about the complexity of issues of oxidative stress. Natural compounds play a serious role in multiple aspects of both human, leading to clear health-promoting effects. This work is focused on the potential application cosmetic formulations containing including but not limited to of clove water and isolated clove oils on their aid in the control of the diseases. The aim of our work was to prepare to evaluate cosmetic formulations containing clove oil, eugenol or new eugenol ester derivative (eugenyl dichloroacetate - EDChA) but also cosmetic formulations containing the aqueous phase obtained after separation of essential oil following the clove buds steam distillation. To evaluate the antioxidants transdermal delivery system, in vitro permeation experiments in a Franz diffusion cell were performed using pig skin. The antioxidative capacity of the cosmetic formulations obtained was determined by the DPPH free radical reduction method. In the next stage, the antioxidant activity (DPPH, ABTS, and Folin–Ciocalteu methods) of the fluid that penetrated through pig skin and of the fluid obtained after skin extraction, were also evaluated. For comparison, studies of cosmetic formulation containing alone dichloroacetic acid (DChAA) were as well carried out. The obtained cosmetic formulations were characterized by of antioxidant activity estimated after 24 hours of conducting the experiment, which indicates long-term protection against reactive oxygen species (ROS) in the deeper layers of the skin. The results of this work contribute to the development of cosmetic formulations with antioxidant potential, emphasizing that the water phases are waste from the process of cloves steam distillation and are not used to prepare cosmetic formulations. The use of waste water from the clove buds steam distillation process is environmentally friendly and not allows us to waste, containing however valuable biologically active compounds (furfural, methyl salicylate, 4-allilofenol, eugenol, α- and β-caryophyllene, eugenyl acetate, β-caryophyllene oxide). Together, these results suggest that cosmetic formulations may be potential drug candidates for chemopreventive, antineoplastic and antimutagenic therapy.
Thu, 8 October 2020
ARTICLE | doi:10.20944/preprints202010.0181.v1
Subject: Chemistry, Analytical Chemistry Keywords: Ethiopia; milk; aflatoxin; Awi zone; HPLC-FLD; Aspergillus
Online: 8 October 2020 (15:53:52 CEST)
The aim of this study, therefore, provides information about Aflatoxin levels in raw cow’s milk in Injibara Town of Awi Administrative zone by using HPLC-FLD. A good linearity of standard calibration was found for AFM1 at a range of 0.5–7 µg/L. Regression coefficient (R2) values were 0.9999, whereas slope and intercept were 2.5278 and 0.1012, respectively. The average recoveries for the spiked samples were range from76.62– 90.98 % and the RSD values ranged between 2.55–7.36 %. The results showed that 15 % of samples (3 out of 20) were contaminated with AFM1 in the range of 0.046–0.22 µg/L. The average contamination level was 0.121 µg/L. The determined mean values of AFM1 in the collected milk samples were above the standard limit of the European Commission and lower than the level established by United States regulations. Further monitoring of Aflatoxin in milk samples from different regions of the country is justified to conclusively determine the actual safe/risks and possibly low Aflatoxins-risk milk production areas.
Tue, 6 October 2020
ARTICLE | doi:10.20944/preprints202010.0139.v1
Online: 6 October 2020 (16:01:57 CEST)
Spin crossover (SCO) complexes are in the forefront of image, memory and sensing devices, with applications already established since for thirty years. In order to reach magnetic multistability conditions, the high-spin (HS) and low-spin (LS) states have to be carefully balanced by ligand field stabilization and spin pairing energies. Both of these effects could be effectively modelled by electronic structure theory, if the description would be accurate enough to describe these concurrent influences to within a few kJ/mol. Such a milestone would allow for the in silico-driven development of SCO complexes. However, so far, the ab initio simulation of such systems has been dominated by general gradient approximation density functional calculations. The latter can only provide the right answer for the wrong reasons, given that the LS states are grossly stabilized. In this contribution, we explore different venues for the parameterisation of hybrid functionals. A fitting set is provided on the basis of explicitly correlated coupled cluster calculations, with single- and multi-dimensional fitting approaches being tested to selected classes of hybrid functionals (hybrid, range separated and local hybrid). Promising agreement to benchmark data is found for a rescaled PBE0 hybrid functional and a local version thereof, with a discussion of different atomic exchange factors.
REVIEW | doi:10.20944/preprints202010.0134.v1
Subject: Chemistry, Analytical Chemistry Keywords: zinc sensor; 8-amidoquinoline; fluorescent probe; chemosensor; systematic review
Online: 6 October 2020 (14:55:13 CEST)
Abundant of preparatory works have recognized that fluorescent sensors based on 8-aminoquinoline are popular tools to detect Zn2+ ions in environmental and biological applications. Along with these studies, researchers started to introduce a variety of carboxamido group into an 8-aminoquinoline molecule in forming 8-amidoquinoline derivatives. Therefore, this systematic review aims to introduce a general overview of the fluorophore 8-aminoquinoline as Zn2+ receptors and to provide comparisons of collected studies that related to 8-amidoquinoline derivatives as fluorophore probe of the sensor. According to PRISMA systematic searches strategy, 13 articles were analyzed for trends, research designs, results and discussion, subject samples, and remarks or conclusions. We found cross-sectional studies with four aspects in zinc sensing that have been targeted; binding studies via titration, detection's limit, interferences studies, and validation of the study. Hence, this paper also included assessments of those criteria and the trends of development of 8-amidoquinoline derivatives based-zinc fluorescent chemosensor. It also showed that most of the researches conducted in China. In conclusion, this study identified various research designs of fluorescent chemosensors based on 8-amidoquinoline prolong with the effectiveness and potential as a recognition probe to assist the detection of zinc. Hence, elucidation of those derivatives essential to be explored because more studies are needed to improve the sensing criteria of the zinc sensor
Subject: Chemistry, Analytical Chemistry Keywords: untargeted metabolomics; internal standard; deoxynivalenol; abiotic stress of wheat; matrix effects
Online: 6 October 2020 (13:37:38 CEST)
Stable isotope-assisted approaches can improve untargeted LC-HRMS metabolomics studies. Here, we demonstrate at the example of chemically stressed wheat that metabolome-wide internal standardization by globally 13C-labeled metabolite extract (GLMe-IS) of experimental-condition-matched biological samples can help to improve coverage of treatment-relevant metabolites and aid in the post-acquisition assessment of putative matrix effects in samples obtained upon different treatments. For this, native extracts of toxin- and mock-treated (control) wheat ears were standardized by the addition of uniformly-13C-labeled wheat ear extracts that were cultivated under similar experimental conditions (toxin-treatment and control) and measured with LC-HRMS. The results show that 996 wheat-derived metabolites were detected with the non-condition-matched 13C-labeled metabolite extract, while another 68 were only covered by the experimental-condition-matched GLMe-IS. Additional testing is performed with the assumption that GLMe-IS enables compensation for matrix effects. Although on average no severe matrix differences between both experimental conditions were found, individual metabolites may be affected as is demonstrated by wrong decisions with respect to the classification of significantly altered metabolites. When GLMe-IS was applied to compensate for matrix effects, 272 metabolites showed significantly altered levels between treated and control samples, 42 of which would not have been classified as such without GLMe-IS.
Mon, 5 October 2020
ARTICLE | doi:10.20944/preprints202010.0105.v1
Online: 5 October 2020 (20:19:21 CEST)
Nitroxyl radical catalysts oxidize alcohols under an applied electric potential. It is possible to quantify the alcohol concentration from the resulting oxidation current. In this work, we evaluated the catalytic activity of nitroxyl radicals (or their corresponding hydroxylamines), including 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) as representative nitroxyl radicals, acetoamido-TEMPO, which shows higher oxidation potential than TEMPO owing to the acetoamido group, AZADO, Nor-AZADO, and NNO as less-hindered bicyclic nitroxyl radicals, and NHPI as an N,N-diacyl-type hydroxylamine, in acetonitrile solution. TEMPO, AZADO and NNO were also evaluated for their ability to oxidize alcohols in organic solvents, and their reactivity was compared with the electrochemical response. The most active NNO was used for electrochemical detection of cyclosporin A, a drug with a hydroxyl group.
ARTICLE | doi:10.20944/preprints202010.0077.v1
Subject: Chemistry, Analytical Chemistry Keywords: acetamide; pyridine; pyrrolidine; piperidine; antibacterial activity; heterocycles
Online: 5 October 2020 (11:51:12 CEST)
A sequence of new acetamide derivatives 9-15 of primary, secondary amine, and para-toluene sulphinate sodium salt have been synthesized under microwave irradiation and assessed in vitro for their antibacterial activity against one Gram-positive and two Gram-negative bacterial species such as S. pyogenes, E. coli, and P.mirabilis using the Mueller-Hinton Agar diffusion (well diffusion) method. The synthesized compounds with significant differences in inhibition diameters and MICs were compared with those of amoxicillin, ampicillin, cephalothin, azithromycin and doxycycline. All of the evaluated acetamide derivatives were used with varying inhibition concentrations of 6.25, 12.5, 37.5, 62.5, 87.5, 112.5 and 125 µg/ml. The results show that the most important antibacterial properties exercised by the synthetic compounds 9 and 11 bearing para-chlorophenyl moiety incorporated into the 2-position moiety of acetamide 2. The molecular structures of the new compounds were determined using FT-IR, 1H-NMR techniques.
ARTICLE | doi:10.20944/preprints202010.0071.v1
Subject: Chemistry, Analytical Chemistry Keywords: ethane-diols; methoxy and dimethoxy ethane; liquid structure; hydrogen bond, XRD; Raman
Online: 5 October 2020 (11:30:46 CEST)
In this study, we report a detailed experimental and theoretical investigation of three glycols, namely ethane-1,2-diol, 2-methoxyethan-1-ol and 1,2-dimethoxy ethane. For the first time, the X-Ray spectra of the latter two liquids was measured at room temperature, and they were compared with the newly measured spectrum of ethane-1,2-diol. The experimental diffraction patterns were interpreted very satisfactorily with molecular dynamics calculations, and suggest that in liquid ethane-1,2-diol most molecules are found in gauche conformation, with intramolecular hydrogen bond between the two hydroxyl groups. Intramolecular H-bonds are established in the mono-alkylated diol, but the interaction is weaker. The EDXD study also evidences strong intermolecular hydrogen-bond interactions, with short O···O correlations in both systems, while longer methyl-methyl interactions are found in 1,2-dimethoxy ethane. X-Ray studies are complemented by micro Raman investigations at room temperature and at 80°C, that confirm the conformational analysis predicted by X-Ray experiments and simulations.
Fri, 2 October 2020
ARTICLE | doi:10.20944/preprints202010.0031.v1
Subject: Chemistry, Analytical Chemistry Keywords: primary fatty acid amides; microfluidics; laser induced fluorescence, bioactive lipids
Online: 2 October 2020 (09:16:13 CEST)
The inherent trace quantity of primary fatty acid amides found in biological systems presents challenges for analytical analysis and quantitation, requiring a highly sensitive detection system. The use of microfluidics provides a green sample preparation and analysis technique through small-volume fluidic flow through micron-sized channels embedded in a PDMS device. Microfluidics provides the potential of having a micro total analysis system where chromatographic separation, fluorescent tagging reactions, and detection are accomplished with no added sample handling. This study describes the development and optimization of a microfluidic-laser indued fluorescence (LIF) analysis and detection system that can be used for the detection of ultra-trace levels of fluorescently tagged primary fatty acid amines. A PDMS microfluidic device was designed and fabricated to incorporate droplet-based flow. Droplet microfluidics have enabled on-chip fluorescent tagging reactions to be performed quickly and efficiently, with no additional sample handling. An optimized LIF optical detection system provided fluorescently tagged primary fatty acid amine detection sub-fmol (436 amol) LODs. The use of this LIF detection provides unparalleled sensitivity, with detection limits several orders of magnitude lower than currently employed LC-MS techniques and might be easily adapted for use as a complementary quantification platform for parallel MS-based -omics studies.
Thu, 1 October 2020
ARTICLE | doi:10.20944/preprints202010.0019.v1
Subject: Chemistry, Analytical Chemistry Keywords: photocatalyst; TiO2/SiO2 composite; solvothermal; silica sand
Online: 1 October 2020 (14:31:31 CEST)
Heavy metals are non-biodegradable and have a high toxicity effect to living things which makes their presence in the environment extremely dangerous. The method of handling heavy metals waste by photocatalysis techniques using TiO2/SiO2 composite showed a good performance in reducing harmful pollutants. In this study, SiO2 from Bengkulu beach sand was used as a support material for TiO2 photocatalyst to reduce Cr(VI) and Pb(II) concentrations. SiO2 was obtained through leaching techniques using NaOH as a solvent. The TiO2/SiO2 composite photocatalyst were synthesized using a solvothermal method at 130 °C and then characterized using XRD, FTIR, SEM and PSA. Based on the XRD diffractogram, the synthesized TiO2 showed the anatase structure while the SiO2 showed the amorphous structure. Ti-O-Si bond is defined in the IR spectra, which indicates that the relationship between TiO2 and SiO2 is a chemical interaction. The results of SEM and PSA characterizations show agglomerated spherical (round) particles with a mean particle size of 616.9 nm. The TiO2/SiO2 composite of 7:1 ratio showed the highest photocatalytic activity after 180 minutes of UV irradiation, with a concentration-decrease percentage of 93.77% and 93.55% for for Cr(VI) and Pb(II), respectively.
Wed, 30 September 2020
ARTICLE | doi:10.20944/preprints202009.0763.v1
Subject: Chemistry, Analytical Chemistry Keywords: ab initio; sulphur dioxide; ozone; dimers; complexes; structures; vibrational spectra.
Online: 30 September 2020 (18:36:52 CEST)
The structures of a number of dimers of sulphur dioxide and ozone have been optimized by means of a series of ab initio calculations. The dimer species have been classified as either genuine energy minima or transition states of first or higher order, and the most probable structures consistent with the experimental data have been confirmed. The molecular orbitals engaged in the interactions resulting in adduct formation have been identified and relations between the orbitals of the dimers of the valence isoelectronic monomer species examined. The vibrational spectra of the most probable structures have been computed, and compared with those reported in the literature, particularly with spectra observed in cryogenic matrices. The calculations have been extended to predict the properties of a number of possible heterodimers formed between sulphur dioxide and ozone.
ARTICLE | doi:10.20944/preprints202009.0762.v1
Subject: Chemistry, Analytical Chemistry Keywords: Bentonite; Phosphogypsum; Slag; Lime; Hydration; Kinetics; Pozzolanic reactions.
Online: 30 September 2020 (18:01:21 CEST)
The Black Steel slag (Ss) and phosphogypsum (PG) are industrial wastes produced in Morocco. In order to reduce these two wastes and to evaluate their pozzolanic reactivity in the presence of water, they were incorporated into bentonite (B) mixed with lime (L). The studied mixtures (BLW, BL-PG-W and BL-PG-Ss-W) were analyzed by X-ray diffraction, Infrared spectroscopy, Raman spectroscopy and SEM/EDX analysis. Compressive strength tests were performed on hardened specimens. The results obtained show that the hydration kinetics of the B-L-W and B-L-PG-W mixtures are slow. The addition of PG to a bentonite-lime mixture induces the formation of new microstructures such as hydrated calcium silicate (C-S-H) and ettringite, which increases the compressive strength of the cementitious specimens. The addition of the Ss to a mixture composed by 8%PG and 8%L-B accelerates the kinetics of hydration and activates the pozzolanic reaction. The presence of C2S in the slag helps to increase the mechanical strength of the mixture B-L-PG-Ss. The compressive strength of the mixtures BL-W, BL-PG-W and BL-PG-Ss-W increases from 15 to 28 days of setting. After 28 days of setting, 8% of Sc added to the mixture 8% PG-8%L-B is responsible for an increase of the compressive strength to 0.6 MPa.
Subject: Chemistry, Analytical Chemistry Keywords: multiscale computation; electron transfer; light harvesting
Online: 30 September 2020 (16:44:21 CEST)
A tremendous effort is currently devoted to the generation of novel hybrid materials with enhanced electronic properties for the creation of artificial photosynthetic systems. This compelling and challenging problem is well-defined from an experimental point of view, as the design of such materials relies on combining organic materials or metals with biological systems like redox-active proteins. Such hybrid systems can be used e.g. as bio-sensors, bio-fuel cells, biohybrid photoelectrochemical cells and nanosctuctured photoelectronic devices. Despite these efforts, the main bottleneck is the formation of efficient interfaces between the biological and the organic/metal counterparts for efficient electron transfer (ET). It is within this aspect that computation can make the difference and improve the current understanding of the mechanisms underneath the interface formation and the charge transfer efficiency. Yet, the systems considered are more and more complex, reaching (and often passing) the limit of current computation power. In this review, recent developments in computational methods for studying complex systems for artificial photosynthesis will be provided and selected cases discussed, to assess the inherent ability of computation to leave a mark in this field of research.
ARTICLE | doi:10.20944/preprints202009.0731.v1
Subject: Chemistry, Analytical Chemistry Keywords: Cosmetic, Heavy metals, Toxicity, Cadmium, Atomic Absorption Spectroscopy.
Online: 30 September 2020 (09:07:14 CEST)
Throughout the ages and times, the need to use everything that reflects women's beauty and helps them maintain their vision and health, and if the need to use the precious materials has been put in place, it is important that they produce the desired results without attention to the harmful chemicals and heavy metals that they contain. Over time, the toxicity of these heavy metals increases in our environment because of their long-term exposure to these pollutants, whether low or high-level in toxicity, animal-prednmost, environment, including air we breathe, water, food, etc. Cosmetics are one of these sources through which humans are exposed to heavy toxic metals. Heavy metals have been estimated in a number of previous studies, and in our study here, we aim to estimate the amount of cadmium metal and study it in various cosmetics such as Lipstick, Eye shadow, Face whitening cream. Two samples were taken from each of the locomoys and cadmium was estimated using the photometer of atomic absorption, one of the samples being expensive and the other low-cost, and purchased from the wholesale markets of Taiz City. Cadmium has been found prominently in these products and the highest rate found in the lowest cost-effective, Eye shadow, that the use of these cosmetic products exposes users to low- conc. heavy metals, which may pose a danger to their health. They are known to be clustered in their biological systems over time, resulting in an imbalance of body and environment. The results found that the low-priced color samples contained a higher concentration of cadmium than the high-price samples in low-priced samples, cadmium concentration was in order of eye shadow > lipstick = face whitening cream. The similar pattern are shown also for higher price product, which are lipstick > face whitening cream > eye shadow.
Tue, 29 September 2020
ARTICLE | doi:10.20944/preprints202009.0703.v1
Subject: Chemistry, Analytical Chemistry Keywords: açaí; total polyphenol; total anthocyanin; antioxidant; elemental analysis; essential elements; biological activity; wound healing
Online: 29 September 2020 (09:14:48 CEST)
Chemical composition analysis of açaí extracts revealed higher levels of total polyphenol content in purple açaí samples for both commercial (4.3 – 44.7 gallic acid equivalents mg/g) and non-commercial samples (30.2 – 42.0 mg/g) compared to white (8.2 – 11.9 mg/g) and oil samples (0.8 – 4.6 mg/g). The major anthocyanin compounds found in purple açaí samples were cyanidin-3-glucoside and cyanidin-3-rutinoside with total concentrations in the range of 3.6 – 14.3 cyanidin-3-glucoside equivalents mg/g. The oligomeric proanthocyanidins were quantified in the range of 1.5 – 6.1 procyanidin B1 equivalents mg/g. Moreover, açaí presented significant levels of calcium, magnesium, manganese, iron, zinc and copper, essential minor and trace elements, in comparison with other berries. All of the açaí extracts at 50 μg/mL potently inhibited the release of reactive oxygen species in lipopolysaccharide-stimulated RAW 264.7 macrophage cells, but none inhibited the release of nitric oxide. Furthermore, all the açaí samples demonstrated potential as wound healing agents due to the high levels of migration activity in human fibroblast cells.
Mon, 28 September 2020
ARTICLE | doi:10.20944/preprints202009.0689.v1
Subject: Chemistry, Analytical Chemistry Keywords: Molecular docking; α-Pyrone; antileukemic; CRM1inhibitors
Online: 28 September 2020 (15:35:00 CEST)
Some α-Pyrone derivatives isolated from Alternaria phragmospora fungus showed promising anti leukemic activities, while others were inactive. CRM1/XPO1 (chromosome region maintenance 1 protein, also called exportin1 or PO1 in humans) has been chosen as a target for antileukemic molecular docking study for those compounds to understand their modes of interaction and structure activity relationships. The results showed that two (2 and 4), out of six, natural α-Pyrone derivatives exhibited well-established interactions with the amino acids of the receptor, which was in agreement with the experimental anti-leukemic results of these compounds. Moreover, twenty hypothetical chemically modified α-Pyrone derivatives (7-27) have been designed. Compounds 7, 8, 22 and 24 showed more efficient docking properties than the previously considered natural compounds.
TECHNICAL NOTE | doi:10.20944/preprints202009.0683.v1
Subject: Chemistry, Analytical Chemistry Keywords: DNA extraction; normal; patients; protocol; frozen blood
Online: 28 September 2020 (10:52:59 CEST)
Herein, we describe a highly efficient, non-complicated, and non-organic procedure to overcome the negative effect of chemotherapeutic drugs on the quality of the extracted DNA by applying several modulations in cell washing, suspension, and lysis of cells treated with these drugs. In this protocol, 500µl were extracted from patients who received systemic sessions of chemotherapy. The validity of this protocol for digestion with restriction endonucleases and both conventional and real-time polymerase chain reaction were tested. This protocol proved obvious purity (1.8±0.02 and 2.1±1.2, for A260/280 and A260/230, respectively) and adequate yields (10±2.24) µg/100 ml. The positive results of validation experiments proved the validity of the extracted DNA for downstream applications of molecular biology. In addition to the proven efficiency of this protocol to extract DNA from normal samples, its validity was also confirmed from patients who were exposed to chemotherapy. This entails a novel approach to extract a molecular biology grade DNA without having inhibitors against enzymes used in digestion, amplification, and subsequent sequencing even after the systemic sessions with several doses of chemotherapy.
Sun, 27 September 2020
ARTICLE | doi:10.20944/preprints202009.0668.v1
Subject: Chemistry, Analytical Chemistry Keywords: magnetic solid-phase extraction; CoFe2O3 Nanoparticles; polyphenol; Lawsone; high-performance liquid chromatography
Online: 27 September 2020 (08:01:06 CEST)
A novel polyphenol‑coated CoFe2O4 system was synthesized as a magnetic adsorbent by chemical oxidative polymerization process for magnetic solid-phase extraction of lawsone. The synthesized nanoadsorbent showed a spherical morphology with diameters under 50 nm by scanning electron microscopy images. The extraction efficiency of this adsorbent was studied towards the extraction of lawsone from saline aqueous solution in dispersion mode. Major parameters including the type and volume of desorption solvent, amount of sorbent, desorption time, extraction time, extraction temperature, ionic strength and pH were optimized. Under the optimum conditions the relative standard deviation in 0.005 µg mL-1 (inter-day n = 6; intra-day: n = 6; and adsorbent to adsorbent n = 4) were obtained as 5.2, 8.07 and 11.7%, respectively. A linear calibration curve in the range of 0.003–0.5 µg mL-1 with R2 = 0.993 was obtained. The limit of detection and limit of quantification of the method were 0.001 µg mL-1 and 0.003 µg mL-1, respectively. The relative recovery percentages were in range of 90-96.4% for henna leaves, henna shampoo, and henna dermal lotion real samples.
ARTICLE | doi:10.20944/preprints202009.0660.v1
Subject: Chemistry, Analytical Chemistry Keywords: metformin cocrystal; mechanochemical synthesis; dicationic metformin; water channels; pi-interactions; mesoporous anhydrate
Online: 27 September 2020 (04:12:17 CEST)
A new cocrystal salt of metformin, an antidiabetic drug, and N,N’-(1,4-phenylene)dioxalamic acid, was synthesized by mechanochemical synthesis, purified by crystallization from solution and characterized by single X-ray crystallography. The structure revealed a salt-type cocrystal composed of one dicationic metformin unit, two monoanionic units of the acid and four water molecules namely H2Mf(HpOXA)2∙4H2O. X-ray powder, IR, 13C-CPMAS, thermal and BET adsorption-desorption analyses were performed to elucidate the structure of the molecular and supramolecurar structure of the anhydrous microcrystalline mesoporous solid H2Mf(HpOXA)2. The results suggest that their structures, conformation and hydrogen bonding schemes are very similar between them. To the best of our knowledge, the selective formation of the monoanion HpOXA⁻, as well as its structure in the solid, is herein reported for the first time. Regular O(-)∙∙∙C(), O(-)∙∙∙N+ and bifacial O(-)∙∙∙C()∙∙∙O(-) of n→* charge-assisted interactions are herein described in H2MfA cocrystal salts which could be responsible of the interactions of metformin in biologic systems. The results, support the participation of n→* charge-assisted interactions independently, and not just as a short contact imposed by the geometric constraint due to the hydrogen bonding patterns.
Sat, 26 September 2020
Subject: Chemistry, Analytical Chemistry Keywords: NMR spectroscopy; honey; honeydew honey; geographical origin; classification
Online: 26 September 2020 (16:58:24 CEST)
Bulgaria and North Macedonia have a long history of production and use of honey, however, there is an obvious lack of systematic and in-depth research on honey from both countries. Of particular interest is the oak honeydew honey, highly valued by consumers because of its health benefits. Aim of this study was to characterize honeydew and floral honeys from Bulgaria and North Macedonia based on their NMR profiles. 1D and 2D 1H and 13C NMR spectra were measured of 16 North Macedonian and 22 Bulgarian honey samples. 25 individual substances were identified, including quinovose, which was found for the first time in honey. Chemometric methods (PCA - principal component analysis, PLS-DA - partial least squares discriminant analysis, ANOVA) were used to detect similarities and differences between samples, as well as to determine their botanical and geographical origin. Semiquantitative data on individual sugars and some other constituents were obtained; which allowed reliable classification of honey samples by botanical and geographical origin, based on chemometric approaches. The results enabled to distinguish oak honeydew honey from other honey types, and to determine the country of origin. NMR was a rapid and convenient method, avoiding the need for other more time-consuming analytical techniques.
ARTICLE | doi:10.20944/preprints202009.0643.v1
Subject: Chemistry, Analytical Chemistry Keywords: dispersion; ketone-alcohol complexes; density functional theory; hydrogen bonds; molecular recognition; vibrational spectroscopy; gas phase; benchmark; pinacolone
Online: 26 September 2020 (14:57:33 CEST)
The influence of distant London dispersion forces on the docking preference of alcohols of different size between the two lone electron pairs of the carbonyl group in pinacolone is explored by infrared spectroscopy of the OH stretching fundamental in supersonic jet expansions of 1:1 solvate complexes. Experimentally, no pronounced tendency of the alcohol to switch from the methyl to the bulkier tert-butyl side with increasing size is found. In all cases, methyl docking dominates by at least a factor of two, whereas DFT-optimized structures suggest a very close balance for the larger alcohols, once corrected by CCSD(T) relative electronic energies. Together with inconsistencies when switching from a C4 to a C5 alcohol, this points at deficiencies of the investigated B3LYP and in particular TPSS functionals even after dispersion correction, which cannot be blamed on zero point energy effects. The search for density functionals which describe the harmonic frequency shift, the structural change and the energy difference between the docking isomers of larger alcohols to unsymmetric ketones in a satisfactory way is open.
Fri, 25 September 2020
ARTICLE | doi:10.20944/preprints202009.0607.v1
Subject: Chemistry, Analytical Chemistry Keywords: Milk Serum; whey proteins; RP-HPLC-UV; free amino acids; RP-HPLC-FLD; antimicrobial study
Online: 25 September 2020 (11:45:09 CEST)
The aim of this study was characterization of some dairy drinks based on Milk Serum regarding major whey proteins (WP) and free amino acids (FAAs) using reversed phase high performance liquid chromatographic (RP-HPLC) methods. The studied WP, -lactalbumin (-La), bovine serum albumin (BSA), -lactoglobulin A (-Lg A) and -lactoglobulin B (-Lg B) were separated on Aeris XB-C18 column at 214 nm detection. The RP-HPLC method was validated by selectivity, linearity (R2 ≥0.99), sensitivity (LOQ, 1.35–10.08 µg mL−1), accuracy (recovery 96.79-103.07%) and precision (% RSD ≤ 4.13%). The total studied WP in studied dairy drinks varied between 1.42 and 3.047 g·L-1. The chromatographic profile of FAAs (aspartic acid, glutamic acid, serine, histidine, arginine, glycine, threonine, alanine, tyrosine, cysteine, tryptophan, methionine, valine, phenylalanine, isoleucine, leucine and lysine) was determined in lyophilized concentrate of Milk Serum by RP-HPLC using pre-column derivatization reaction with orthophthalaldehyde (OPA). The total studied FAAs in studied samples varied between 1.103 and 1.119 mg·g-1. Moreover, the Milk Serum showed bacteriostatic activity against two bacterial strains Escherichia coli and Staphylococcus aureus. The obtained results confirm that dairy drinks based on the Milk Serum constitutes a valuable sources of bioactive components with benefits for human healthy nutrition.
Tue, 22 September 2020
ARTICLE | doi:10.20944/preprints202009.0523.v1
Subject: Chemistry, Analytical Chemistry Keywords: Anticancer; Tubulin; HSP27; Nimesulide; SKOV3; SKBR3
Online: 22 September 2020 (15:19:02 CEST)
Tubulin and heat shock protein 27 (HSP27) are up-regulated in cancer cells, and play a critical role in cell division, and proliferation. Therefore, they are targets for discovery of anticancer therapy. The objective of this study is to design, characterize, and biologically evaluate the nimesulide analogues to combat female cancer such as ovarian cancer, and breast cancer. Herein, the nimesulide analogues are designed to target both tubulin and HSP27 functions. Ovarian cancer (SKOV3) and breast cancer (SKBR3) cell lines were used as surrogate models to test the nimesulide analogs biological activities using MTT assay. In the present study, four nimesulide analogues were designed, synthesized and the chemical structures were with the biological evaluation were studied. The synthesized agents were characterized by 1H-NMR, 13C-NMR, the molecular weight was confirmed using GC-MS technique, and melting point. Besides, the agent L4 structure was confirmed using X-ray crystallographic analysis. The present data revealed that nimesulide analogs have potent anticancer activity against SKOV3and SKBR3 cell lines. The IC50 values for both SKOV3 and SKBR3 cell lines treated with the agents showed a potent cell growth inhibition range of 0.23-2.02 µM and 0.50-3.73 µM respectively. In conclusion, the designed nimesulide analogues can target both tubulins, and HSP27 concurrently, and they are promising agents as future chemotherapy female cancers.
Tue, 8 September 2020
Subject: Chemistry, Analytical Chemistry Keywords: glycolipidomics; GIPC; glycosyl inositol phospho ceramides; Lipid Data Analyzer; lipidomics; sphingolipids; ultra-high pressure liquid chromatography; high-resolution mass spectrometry; LC-MS; automated annotation
Online: 8 September 2020 (12:34:56 CEST)
Glycosyl inositol phospho ceramides (GIPCs) are the major sphingolipids on earth as they account for a considerable fraction of the total lipids in plants and fungi which in turn represent a large portion of the biomass on earth. Despite their obvious importance, GIPC analysis remains challenging due to the lack of commercial standards and automated annotation software. In this work, we introduce a novel GIPC glycolipidomics workflow based on reversed-phase ultra-high pressure liquid chromatography coupled to high-resolution mass spectrometry. For the first time, automated GIPC assignment was performed using the open-source software Lipid Data Analyzer based on platform-independent decision rules. Four different plant samples (salad, spinach, raspberry, strawberry) were analyzed and revealed 64 GIPCs based on accurate mass, characteristic MS2 fragments and matching retention times. Relative quantification using lactosyl ceramide for internal standardization revealed GIPC t18:1/h24:0 as the most abundant species in all plants. Depending on the plant sample, GIPCs contained mainly amine, N-acetylamine or hydroxyl residues. Most GIPCs revealed a Hex-HexA-IPC core and contained a ceramide part with a trihydroxylated t18:0 or t18:1 long chain base and hydroxylated fatty acid chains ranging from 16 to 26 carbon atoms in length (h16:0 – h26:0). Interestingly, six GIPCs containing t18:2 were observed in raspberry, which was not reported so far. The presented workflow supports the characterization of different plant samples by automatic GIPC assignment potentially leading to the identification of new GIPCs. For the first time, automated high‑throughput profiling of these complex glycolipids is possible by liquid chromatography-high-resolution mass spectrometry and subsequent automated glycolipid annotation based on decision rules.
Thu, 3 September 2020
ARTICLE | doi:10.20944/preprints202009.0070.v1
Subject: Chemistry, Analytical Chemistry Keywords: inactivation column test; silanol; trace metals; in silico; bonded-phase silica
Online: 3 September 2020 (11:41:25 CEST)
The silanol activity and trace metal detection methods for chemically bonded silica gels were evaluated in silico. Test compounds with large molecular sizes may demonstrate negative results because of the possibility of indirect hydrogen bonding via short alkyl groups or siloxane of the silica gels. This hypothesis was based on the observation of weak hydrogen bonding energy values similar to those observed in the study of the alkyl group effect on the hydrogen bonding of alkanols. Consequently, smaller molecules may be a better choice for the analysis of bonded-phase quality.
Wed, 2 September 2020
ARTICLE | doi:10.20944/preprints202009.0007.v1
Subject: Chemistry, Analytical Chemistry Keywords: Basic drugs; selective bonded-phase; in silico; solvent effect; electron localization
Online: 2 September 2020 (04:20:56 CEST)
Abstract: The quantitative analysis of the chromatographic behavior of basic compounds was performed in silico. The liquid chromatography (LC) data measured with pentyl-, hexenyl-, and octyl-bonded silica gels were analyzed in silico employing model phases. The main retention force was the van der Waals (VW) interaction, and the main desorption force was an electrostatic (ES) interaction. The contribution of hydrogen bonding (HB) was weak compared to that for acidic compounds. The quantitative explanation was achieved utilizing the calculated VW, HB, and ES energy values obtained from a molecular mechanics program. The electron localization was observed at the molecular interaction-site calculated MOPAC program. This fundamental approach was like that of explaining chemical reactions. The difference was electron localization in chromatography or electron transfer in a chemical reaction.
Wed, 26 August 2020
Subject: Chemistry, Analytical Chemistry Keywords: Howard Flack; Flack Parameter; Structure Analysis; X-ray Crystallography
Online: 26 August 2020 (05:01:13 CEST)
The Flack Parameter is now almost universally reported for all chiral materials characterized by X-ray crystallography. It’s elegantly simplicity was an inspired development by Flack, and although the original algorithm for its computation has been strengthened by other workers, it remains an essential outcome for any crystallographic structure determination. As with any one-parameter metric, it needs to be interpreted in the context of its standard uncertainty.
Tue, 25 August 2020
ARTICLE | doi:10.20944/preprints202008.0533.v1
Subject: Chemistry, Analytical Chemistry Keywords: sulfamethoxazole; differential pulse voltammograms; cyclic voltammetry; molybdenum; nanoparticle; TMP
Online: 25 August 2020 (03:24:09 CEST)
Manganese and Molybdenum oxides are well-known electro-catalysts in fuel cells systems; they are usually used as anodic materials for the oxidation of low molecular weight alcohols. The utilization of MoO2 and MnO2 as catalysts in the pharmaceutical analysis is not common yet an analytical method for the determination of Sulfamethoxazole (SMX) antibacterial agents in Pharmaceutical Dosage form is developed. The method is based on the voltammetric determination of SMX using modified glassy carbon electrode by molybdenum oxide. The two components are oxidized at the modified electrode surface with the development of current that is linearly proportional to their concentrations in the range of 7.04*10-7- 1*10-3 M for SMX. The oxidation reaction of the two components is pH-dependent, in which the buffer used is Britton-Robinson at pH = 7.00 where maximum peak current and maximum peak separation is obtained. The regression factors obtained from the calibration curves are 0.9790 for SMX and 0.9812 for TMP. The method of analysis was validated, where the limit of detection (LOD) and the limit of quantitation (LOQ) of SMX were calculated to be 1.44*10-4 M, 4.36*10-4 M and 1.27*10-4 M, 3.84*10-4 M respectively, The percentage recovery of both components was also calculated to 81 % for SMX.
Thu, 13 August 2020
COMMUNICATION | doi:10.20944/preprints202008.0297.v1
Subject: Chemistry, Analytical Chemistry Keywords: cat urine; odor mitigation; odor; volatile organic compounds; emission; indoor air quality, solid-phase microextraction; SPME; diffusion; Micrococcus luteus
Online: 13 August 2020 (08:51:58 CEST)
Urination on carpet and subflooring can develop into persistent and challenging to mitigate odor. Very little or no information is published on how these VOCs change over time when urine is deposited on the carpet covering a plywood-type subflooring. This research has investigated the VOCs emitted from carpet+subflooring (control), carpet+subflooring sprayed with water (control with moisture), and cat urine-contaminated carpet+subflooring (treatment) over time (day 0 and 15). In addition, the effect of popular cleaning products on VOCs emitted and evaluated their efficacy in eliminating those indoor odors over time (day 0 and 15). Carpet-subflooring with all treatments were also contaminated with Micrococcus luteus, nonmotile obligate aerobe commonly found in household dust, to observe the impact of the aerobe on carpet-subflooring VOCs emission. VOCs emitted from carpet+subflooring receiving different treatments were collected from headspace using solid-phase microextraction (SPME). The VOCs were analyzed using a multidimensional gas chromatography-mass spectrometer attached to an olfactometry (GC-MS-O). Many common VOCs were released from the carpet on day one and day fifteen, specifically from urine contamination. Cleaning products were effective in masking several potent odors of cat urine contaminated carpet VOCs on day one but unable to remove the odor appeared on day 15 in most cases.
Wed, 12 August 2020
ARTICLE | doi:10.20944/preprints202008.0282.v1
Subject: Chemistry, Analytical Chemistry Keywords: cyanobacteria; cyanopeptides; eutrophication; harmful bloom; liquid chromatography tandem mass spectrometry; Global Natural Product Social networking (GNPS); Dereplication strategy.
Online: 12 August 2020 (10:15:46 CEST)
Man-made shallow fishponds in the Czech Republic have been facing a high eutrophication since 1950s. Anthropogenic eutrophication and feeding of fish have strongly affected the physico-chemical properties of water and its aquatic community composition leading to harmful algal bloom formation. In our current study, we have characterised the phytoplankton community across three hypertrophic ponds to assess the phytoplankton dynamics during the vegetation season. We microscopically identified and quantified 29 cyanobacterial taxa comprised of non-toxigenic and toxigenic species. Further, a detailed cyanopeptides (CNPs) profiling was performed using molecular networking analysis of liquid chromatography tandem mass spectrometry (LC–MS/MS) data coupled with dereplication strategy. This MS networking approach coupled with dereplication on online global natural product social networking (GNPS) web platform led us to putatively identify forty CNPs: fourteen anabaenopeptins, ten microcystins, five cyanopeptolins, six microginins, two cyanobactins, a dipeptide radiosumin, a cyclooctapeptide planktocyclin and epidolastatin12. We have applied the binary logistic regression to estimate the CNPs producer by correlating the GNPS data with the species abundance. Usage of The combination of molecular networking and dereplication on online global natural product social networking (GNPS) web platform has proved as a valuable approach for rapid and simultaneous detection of high number of peptides, and rapidly assessing the risk for harmful bloom.
Sun, 2 August 2020
ARTICLE | doi:10.20944/preprints202008.0025.v1
Subject: Chemistry, Analytical Chemistry Keywords: HPLC method; Curcumin; Quercetin; Thermal analysis; Nanoemulsion
Online: 2 August 2020 (12:15:13 CEST)
Biphasic oily/water nanoemulsions have been proposed as delivery systems for the intranasal administration of curcumin (CUR) and quercetin (QU), due to their high drug entrapment efficiency, the possibility of simultaneous drug administration and protection of the encapsulated compounds from the degradation. To better understand the physicochemical and biological performance of the selected formulation simultaneously co-encapsulating CUR and QU, a stability test of the compounds mixture was firstly carried out using X-ray powder diffraction and thermal analyses, such as differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA). The determination and quantification of the encapsulated active compounds was then required being an essential tool for the development of innovative nanomedicines. Thus, a new HPLC–UV/Vis method for the simultaneous determination of CUR and QU in the nanoemulsions and their evaluation in stability studies in simulated biological fluids was developed and validated. The X-ray diffraction analyses demonstrated that no interaction between the mixture of active ingredients, if any, is strong enough to take place in the solid state. Moreover, the thermal analysis demonstrated that the CUR and QU are stable in the nanoemulsion production temperature range. The proposed analytical method for the simultaneous quantification of the two actives was selective and linear for both compounds in the range of 0.5 – 12.5 µg/mL (R2 > 0.9997), precise (RSD below 3%), robust and accurate (recovery 100 ± 5 %). The method was validated in accordance with ICH Q2 R1 “Validation of Analytical Procedures” and CDER-FDA 2validation of chromatographic methods” guideline. Furthermore, the low detection (LOD < 0.005 µg/mL for CUR and <0.14 µg/mL for QU) and quantification limits (LOQ < 0.017 µg/mL for CUR and < 0.48 µg/mL for QU) of the method were suitable for the application to drug release and permeation studies planned for the development of the nanoemulsions. The method was then applied for the determination of nanoemulsions CUR and QU encapsulation efficiencies (> 99%), as well as for the stability studies of the two compounds in simulated biological fluids over time. The proposed method represents, to our knowledge, the only method for the simultaneous quantification of CUR, and QU in nanoemulsions.
Thu, 23 July 2020
ARTICLE | doi:10.20944/preprints202007.0562.v1
Subject: Chemistry, Analytical Chemistry Keywords: Brasilonema; Anabaenopeptins; hexapeptides; tryptophan-containing peptides; molecular networking; antiproliferative activity
Online: 23 July 2020 (12:40:38 CEST)
Heterocytous cyanobacteria are among the most prolific source of bioactive secondary metabolites, including anabaenopeptins (APTs). A terrestrial filamentous Brasilonema sp. CT11 collected in Costa Rica bamboo forest, as black mat was studied using a multidisciplinary approach: genome mining and HPLC-HRMS/MS coupled with bionformatic analyses. Herein, we report the nearly complete genome consisting 8.79 Mbp with a GC content of 42.4%. Moreover, we report on three novel tryptophane-containing APTs; anabaenopeptin 788 (1), anabaenopeptin 802 (2) and anabaenopeptin 816 (3). Further, the structure of two homologues, i.e., anabaenopeptin 802 (2a) and anabaenopeptin 802 (2b) was determined by spectroscopic analysis (NMR and MS). Both compounds were shown to exert weak to moderate antiproliferative activity against HeLa cell lines. This study also provides the unique and diverse potential of biosynthetic gene clusters and an assessment of the predicted chemical space yet to be discovered from this genus.
Fri, 17 July 2020
Subject: Chemistry, Analytical Chemistry Keywords: mixed oxide-LDHs; manganese; wastewater; adsorption kinetics
Online: 17 July 2020 (09:14:45 CEST)
In this study, Mg-Al and Mg-Al-Ni - layered double hydroxides (LDHs) were successfully synthesized for efficient removal of Mn2+ from synthetically wastewater. LDH adsorbents (Mg-Al and Mg-Ni-Al) were prepared by co-precipitation method. The formation of the layered double hydroxide, the adsorption of manganese on both LDH (Mg-Al and Mg-Ni-Al) were observed by XRD, SEM and EDX analysis. The various parameters such as the effect of shaking time, initial Mn2+ concentration, temperature were controlled and optimized to removal of Mn2+ from synthetic wastewater. The kinetics and adsorption isotherms for Mn2+ removal from wastewater were studied in batch mode. At temperatures of 10 °C and 20 °C the adsorption equilibrium was reached after 24 h. Adsorption isotherms of Mn2+ are well fitted by Langmuir and Freundlich isotherm equation. The adsorption capacity of Mn2+ from synthetic wastewater of 80.607 mg/kg was obtained for (Mg-Al-Ni)-LDH. It is found that the adsorption kinetics is best described by the pseudo-second order model. These results prove that LDHs can be considered as a potential material for adsorption of Mn2+ from wastewater.
Sun, 28 June 2020
ARTICLE | doi:10.20944/preprints202006.0342.v1
Subject: Chemistry, Analytical Chemistry Keywords: Heavy metal; Platinum electrode; Ion beam sputtering deposition; Nanoparticle; IBSD; Ion detection
Online: 28 June 2020 (19:31:19 CEST)
An electrochemical sensing platinum nanoparticle in the tantalum electrode is provided by means of an Ion Beam Sputtering Deposition (IBSD). The electrode was made with a Pt solution, sputtered simultaneously with hydrochloric acid corrosion on tantalum substrate. In the study of heavy metal ions, for example, the platinum nanoparticle electrodes as prepared were used Square wavelength voltammetry (OSWV) Hg2+, Cu2+ and Ag2+. The porous electrodes were observed in a broader range by the Pt nanostructure electrode for heavy metal ions. Furthermore, the susceptibility to detection has been shown to be saturated as the thickness of the layer electrode exceeded 50 nm. For Hg2+ 0,003-1 M, for Cu2+ 0,005-3 M and for Ag2+ the linear detection scale is 0,009-4 M. There has also been good reusability and repeatability. In addition, a scan electron microscope (SEM) used to study platinum electrode forming process and nanostructure. This electrode will have interesting applications in sensing systems.
Sun, 14 June 2020
ARTICLE | doi:10.20944/preprints202006.0179.v1
Subject: Chemistry, Analytical Chemistry Keywords: Heavy metal; Platinum electrode; Ion beam sputtering deposition; Nanoparticle; IBSD; Ion detection
Online: 14 June 2020 (14:46:10 CEST)
Today, contamination from heavy metals in the atmosphere is a global concern. Efficient detection techniques are therefore necessary if heavy metal exposure levels in different media are to be determined. The voltammetry method for in situ detection of heavy metal ions is a very sensitive electrochemical method. This thesis explores emerging developments in electrode alteration, materials production and experimental optimization. An electrochemical sensing platinum nanoparticle in the tantalum electrode is provided by means of an Ion Beam Sputtering Deposition (IBSD). The electrode was made with a Pt solution, sputtered simultaneously with hydrochloric acid corrosion on tantalum substrate. In the study of heavy metal ions, for example, the platinum nanoparticle electrodes as prepared were used Square wavelength voltammetry (OSWV) Hg2+, Cu2+ and Ag2+. The porous electrodes were observed in a broader range by the Pt nanostructure electrode for heavy metal ions. Furthermore, the susceptibility to detection has been shown to be saturated as the thickness of the layer electrode exceeded 50 nm. For Hg2+ 0,003-1 M, for Cu2+ 0,005-3 M and for Ag2+ the linear detection scale is 0,009-4 M. There has also been good reusability and repeatability. In addition, a scan electron microscope (SEM) used to study platinum electrode forming process and nanostructure. This electrode will have interesting applications in sensing systems.
ARTICLE | doi:10.20944/preprints202006.0177.v1
Subject: Chemistry, Analytical Chemistry Keywords: Hydrochlorothiazide; Differential pulse voltammograms; Cyclic Voltammetry; Molybdenum; Modified electrode
Online: 14 June 2020 (14:40:00 CEST)
Molybdenum oxides is well-known electro-catalysts in fuel cells systems, they are usually used as anodic materials for the oxidation of low molecular weight alcohols. The utilization of Mo as catalysts in the pharmaceutical analysis is not common yet. In this study, bare glassy carbon electrodes were modified by the oxides by means of electrochemical deposition and the modified electrodes were used as catalysts for the electrochemical oxidation of hydrochlorothiazide (HCT). Well-resolved anodic peaks were reported for the analyzed pharmaceuticals when the Mo/GCE was utilized for the analysis of HCT. Analytical performance of the modified electrodes was evaluated based on the following statistical parameters; linearity ranges, correlation coefficients, limits of detection and quantitation, and recovery values. The prepared electrodes were used for the determination of the active ingredients in their pharmaceutical formulations and the reported activity was correlated to influence of the utilized pH on both structures of the used electrodes and the detected analytes.
Thu, 4 June 2020
ARTICLE | doi:10.20944/preprints202006.0023.v1
Subject: Chemistry, Analytical Chemistry Keywords: Nymphaea lotus L.; stamen; ultrasound-assisted extraction; macroporous resin (MPR) purification; in vitro; in cellulo; antioxidant; flavonoids
Online: 4 June 2020 (03:59:58 CEST)
Nymphaea lotus L. is the medicinal plant that has long been used as food, cosmetic and traditional medicines in Africa and Asia since the ancient time. Its flavonoids and other interesting phytochemical compounds from rhizome, leaf, and the whole flowers have been reported in the previous published researches. However, stamens, which are essential for reproductive functions, may also represent new alternative sources of potential antioxidant flavonoids as investigated in this study. The innovative green chemistry method i.e. ultrasound-assisted extraction (USAE) as well as macroporous resin (MPR) purification procedure were employed in this current research. The optimal ultrasound-assisted extraction condition is 90 % (v/v) aqEtOH with 34.65 khz ultrasonic frequency and 46 minutes of extraction time. Comparing with heat reflux extraction (HRE) conventional method, the significant gain of 1.35 total flavonoids content was obtained using optimized USAE conditions, jumping to 2.80 when this USAE associated with MPR purification. Not only in vitro cell free antioxidant activity of N. lotus stamen extracts, but also in cellulo antioxidant investigation using yeast model showed the same trend to indicate that the best antioxidant flavonoid can be found in USAE coupled with MPR purification. Moreover, the key antioxidant genes expression in yeast model such as SIR2 and SOD2 were also expressed at the highest level in yeast cell treated with the extract from USAE together with MPR purification. Consequently, it can be seen that the USAE combined with MPR purification can help to enhance the flavonoids antioxidant potential of the stamens extract from this medicinal species.
Sun, 24 May 2020
ARTICLE | doi:10.20944/preprints202005.0402.v1
Subject: Chemistry, Analytical Chemistry Keywords: electrical conductivity; volcanic tuff; cyclic voltammetry; conductivity nanoparticle; platinum electrode
Online: 24 May 2020 (19:17:53 CEST)
This paper has experimentally measured volcanic tufa electrical conductance. The calculations are carried out in accordance with the potential of cyclic voltammetry in a constant state. The cyclic voltammograms nanoelectrode platinum prepared electrochemically were examined in the range -0.2 to 1.2 V vs. AgCl [Cl-]:1.0 M in the presence and absence of volcanic tuff in the aqueous solution of 1.0 M HCl. The cyclic voltammetry studies show that the Nano platinum film suffers degradation when the potential exceeds +0.85 V, and below this potential, it is quite stable. The redox reaction of the electrode is reversible. The nanoparticle platinum synthesized at low temperature and high acid concentration exhibits higher electronic conductivities. It has been observed that, relative to area under the peak aggregate tests, the use of volcanic concrete was showing a large increase in electrical conductivity. It was shown that with cyclic voltammetry, three well-defined anode peak could be achieved at a power of 0.0, 0.4 and 0.6 V versus Ag/AgCl.
Tue, 5 May 2020
ARTICLE | doi:10.20944/preprints202005.0071.v1
Subject: Chemistry, Analytical Chemistry Keywords: COVID-19; coronavirus; SARS-CoV-2; Simultaneous surveillance; Jordan
Online: 5 May 2020 (10:57:53 CEST)
The outbreak of coronavirus 2 (SARS-CoV-2) has already taken on pandemic proportions and has affected more than 100 countries in recent weeks. It is imperative that global healthcare systems are prepared. Containment initiatives in Jordan, on the other hand, have decreased new cases by over 63%. The Jordanian national health system has been very pleased with its ability to adequately meet the needs of the patients diagnosed with SARS-CoV-2 pneumonia, and includes intensive care. From 2 March to 14 April 2020, between 4% and 8% of active infected patients in Jordan registered daily in intensive care. The percentage is very low.
ARTICLE | doi:10.20944/preprints202005.0069.v1
Subject: Chemistry, Analytical Chemistry Keywords: Platinum Electrode; Nanoparticle; Heavy metal; Square Wave Voltammetry
Online: 5 May 2020 (10:45:05 CEST)
The copper deposition on the platinum and palladium nanoelectrode has been studied using cyclic voltammetry. The use of nanoelectrode platinum and palladium are defined in the study of heavy metals. The noble nanoelectrode of metal has a typical silicone processing structure. In comparison to the nanoelectrodes, the geometry of the electrode series is complex and balanced. Nanoelectrodes of platinum are found effective in detecting heavy metal. There was regular analysis of the use of the sensors. The identification constraints down to the ng /L level was accomplished by refined electrode geometry and the stripping procedures. The process was used for the study of water sample determination. Another heavy metal ion attack voltammetric reaction was studied. The SEM picture clearly observed and characterized the nanoparticle electrode by X-ray diffraction and cyclic voltammetry.
Mon, 27 April 2020
ARTICLE | doi:10.20944/preprints202004.0472.v1
Subject: Chemistry, Analytical Chemistry Keywords: 3-D printing; additive manufacturing; distributed manufacturing; laboratory equipment; open hardware; open source; open source hardware; scale; balance; mass
Online: 27 April 2020 (02:59:34 CEST)
This study provides designs for a low-cost, easily replicable open source lab-grade digital scale that can be used as a precision balance. The design is such that it can be manufactured for use in most labs throughout the world with open source RepRap-class material extrusion-based 3-D printers for the mechanical components and readily available open source electronics including the Arduino Nano. Several versions of the design were fabricated and tested for precision and accuracy for a range of load cells. The results showed the open source scale was found to be repeatable within 0.1g with multiple load cells, with even better precision (0.01g) depending on load cell range and style. The scale tracks linearly with proprietary lab-grade scales, meeting the performance specified in the load cell data sheets, indicating that it is accurate across the range of the load cell installed. The smallest loadcell tested(100g) offers precision on the order of a commercial digital mass balance. The scale can be produced at significant cost savings compared to scales of comparable range and precision when serial capability is present. The cost savings increase significantly as the range of the scale increases and are particularly well-suited for resource-constrained medical and scientific facilities.
Fri, 7 February 2020
ARTICLE | doi:10.20944/preprints202002.0088.v1
Subject: Chemistry, Analytical Chemistry Keywords: structural mass spectrometry; protein structure; chemical cross-linking; disuccinimidyl glutarate; bis(sulfosuccinimidyl) glutarate; bovine serum albumin
Online: 7 February 2020 (02:54:08 CET)
The combination of chemical cross-linking and mass spectrometry is currently a progressive technology for deriving structural information of proteins and protein complexes. In addition, chemical cross-linking is a powerful tool for stabilizing macromolecular complexes for single particle cryo-electron microscopy. Broad pallets of cross-linking chemistry, currently available for the majority of cross-linking experiments, still rely on the amine-reactive N-hydroxysuccinimide esters targeting mainly N-termini and lysine side chains. These cross-linkers are divided into two groups: water soluble and water insoluble; and research teams prefer one or another speculating on the benefits of their choice. However, the effect of cross-linker polarity on the outcome of cross-linking reaction has never been studied. Herein, we use both polar (bis(sulfosuccinimidyl) glutarate) and non-polar (disuccinimidyl glutarate) cross-linkers and systematically investigated the impact of cross-linker hydrophobicity on resulting distance constraints, using bovine serum albumin as a model protein.
Fri, 31 January 2020
ARTICLE | doi:10.20944/preprints202001.0373.v1
Subject: Chemistry, Analytical Chemistry Keywords: carbon nanostructures; nanodiamonds; metal nanoparticles; functionalization electrochemical (bio)sensor; nanocomposites
Online: 31 January 2020 (02:13:31 CET)
The incorporation of nanomaterials on (bio)sensors based on composite materials has led to important advances in analytical chemistry field due to the extraordinary properties that these materials offer. Nanodiamonds (NDs) are a novel type of material that has raised much attention, as they have the possibility of being produced on large scale by using relatively inexpensive synthetic methodologies. Moreover, NDs present some other interesting features as suitability for fluorescence due to surface functionalization and a proved biocompatibility, which makes them well suited for biomedical applications. In addition, NDs can be modified with metallic nanoparticles (NP), such as silver or gold, in order to combine the special features of both. The aim of this research work is the nanostructuration of novel sensing devices using NDs combined with silver ([email protected]) and gold ([email protected]) nanoparticles. A complete morphological and electrochemical characterization as function of the prepared nanocomposite composition have been performed in order to improve the electroanalytical properties of the developed (bio)sensors.
Sat, 11 January 2020
ARTICLE | doi:10.20944/preprints201911.0211.v2
Subject: Chemistry, Analytical Chemistry Keywords: polypyrrole; diazonium; multiwalled carbon nanotubes; chelator; heavy metal ions; electrochemical sensors
Online: 11 January 2020 (13:19:11 CET)
Highly sensitive multicomponent materials designed for the recognition of hazardous compounds request control over interfacial chemistry. The latter is key parameter in the construction of the sensing (macro)molecular architectures. In this work, multi-walled carbon nanotubes (in short, CNTs) were deposited on diazonium-modified flexible ITO electrodes prior to electropolymerization of pyrrole. This three step process, including diazonium electroreduction, deposition of CNTs and electropolymerization, provided adhesively bonded polypyrrole-wrapped CNT composite coatings on aminophenyl-modified flexible ITO sheets. The aminophenyl (AP) groups were attached to ITO by electroreduction of the in situ generated aminobenzenediazonium compound in aqueous, acidic medium. For the first time, polypyrrole (PPy) was electrodeposited in the presence of both benzenesulfonic acid (dopant) and ethylene glycol-bis(2-aminoethylether)-tetraacetic acid (EGTA) which acts as a chelator. The flexible electrodes were characterized by XPS, Raman and scanning electron microscopy (SEM) which provided strong supporting evidence for the wrapping of CNTs by the electrodeposited PPy. Indeed, the CNT average diameter increased from 182.6 nm to 274.8, 35.65.9 and 17520.1 after 1, 5 and 10 of electropolymerization of pyrrole. The PPy/CNT/NH2-ITO films generated by this strategy exhibit significantly improved stability and higher conductivity compared to a similar PPy coating without any embedded CNTs as assessed by from electrochemical impedance spectroscopy measurements. The potentiometric response was linear in the 10-83×10-7 mol.L-1 Pb(II) concentration range and the detection limit was 2.9×10-9 mol.L-1 at S/N=3. The EGTA was found to drastically improve selectivity for Pb(II) over Cu(II). To account for this improvement, density functional theory (DFT) was employed to calculate the EGTA-metal ion interaction energy which was found to be -374.6 and -116.4 kJ/mol for Pb(II) and Cu(II), respectively, considering solvation effects. This work demonstrates the power of a subtle combination of diazonium coupling agent, CNTs, chelators and conductive polymers to design high-performance electrochemical sensors for environmental applications.
Sun, 5 January 2020
ARTICLE | doi:10.20944/preprints202001.0043.v1
Subject: Chemistry, Analytical Chemistry Keywords: biosensors; cyclic voltammetry; electrochemical sensors; extracellular electron transfer; extracellular polymeric substances; growth curve; microbial growth phases
Online: 5 January 2020 (16:23:51 CET)
Microbial growth has been of prime importance to the researchers in health and biotechnology industries. It has been known to be closely associated to the secretion of extracellular polymeric substances that help in the formation of colonies. Inter-microbial communication happens within such colonies by means of extracellular electron transfer mediated by the aforementioned polymeric substances. Conventionally, different phases of microbial growth are monitored with the aid of a traditional UV-Visible spectrophotometer by measuring the optical density of the liquid medium at 280 nm. In this paper, we have developed an alternative novel way to sense different growth phases employing electrochemical means i.e. two-terminal cyclic voltammetry. This cyclic voltammetry relies on the extracellular electron transfer mechanism taking place via the polymeric substances secreted by the microorganisms, measured by the temporal area changes in the current-voltage hysteresis curves in the inoculated nutrient broth. This work paves a new way to detect the biological activity in the medium, which can be directly correlated to the population of microorganisms. It would be of immense interest to scientists and researchers working in the field of microbiology as well as in development of biosensors, electrochemical sensors etc. which would be helpful in absence of traditional spectrophotometers.
Tue, 31 December 2019
ARTICLE | doi:10.20944/preprints201912.0416.v1
Subject: Chemistry, Analytical Chemistry Keywords: multiparametric assay; rapid tests; immunochromatography; antibiotics; non-equilibrium interactions
Online: 31 December 2019 (16:25:33 CET)
The presented study is focused on the impact of binding zones locations at immunochromatographic test strips into analytical parameters of multiplex lateral flow assay. Due to non-equilibrium conditions for such assays the duration of immune reactions influences significantly on analytical parameters, and the integration of several analytes into one multiplex strip may cause essential decrease of sensitivity. To choose the best location of binding zones, we have tested reactants for immunochromatographic assays of lincomycin, chloramphenicol, and tetracycline. The influence of the distance to the binding zones on the intensity of coloration and limit of detection (LOD) was rather different. Basing on the obtained data, the best order of binding zones was chosen. In comparison with non-optimal location the LODs were 5-10 fold improved. The final assay provides LODs 0.4, 0.4 and 1.0 ng/mL for lincomycin, chloramphenicol, and tetracycline, respectively. The proposed approach can be applied for multiassays of other analytes.
Wed, 4 December 2019
REVIEW | doi:10.20944/preprints201912.0034.v1
Subject: Chemistry, Analytical Chemistry Keywords: graphene; graphene derivative; biosensor; detection; biomarker
Online: 4 December 2019 (03:00:03 CET)
The development of biosensors with high sensitivity and low-detection limits provides a new direction for medical and personal care. Graphene and graphene derivatives have been used to prepare various types of biosensors due to their excellent sensing performance (e.g. high specific surface area, extraordinary electronic properties, electron transport capabilities and ultrahigh flexibility). This perspective review focuses on graphene-based biosensors for quantitative detection of cancer related biomarkers such as DNA, miRNA, small molecules and proteins by integrating with different signal outputting approaches including fluorescent, electrochemistry, surface plasmon resonance, surface enhanced Raman scattering etc. The article also discussed their challenges and potential solutions along with future prospects.
Sun, 17 November 2019
ARTICLE | doi:10.20944/preprints201911.0207.v1
Subject: Chemistry, Analytical Chemistry Keywords: conducting polymers; metal nanoparticles; gas sensor; hydrogen sulfide gas
Online: 17 November 2019 (14:21:38 CET)
This research paper presents a new application of electroactive polyimide doped with gold nanoparticles (PI/AuNPs) as a chemiresistor sensor for detecting hydrogen sulfide gas. The synthesis of PI/AuNPs was done in a simple 3-step process of polymerization using the as prepared amine-capped aniline trimer (ACAT), followed by imidization, and doping. Spectral analyses via FTIR, LC-MS and 1H-NMR confirmed the formation of amine-capped aniline trimer with a MW of 288 g mol-1. Comparison of ACAT, BSAA, and PI FTIR spectra showed successful polymerization of the last, while XRD validated the incorporation of metal nanoparticles onto the polymer matrix showing characteristic diffraction peaks corresponding to gold. Furthermore, TEM, and FE-SEM revealed the presence of well-dispersed Au nanoparticles with an average diameter of about 60nm. The electroactive PI/AuNPs-based sensor showed a sensitivity of 0.29% ppm-1 H2S at a linear concentration range of 50 to 300 ppm H2S (r = 0.9777). The theoretical limit of detection was found at 0.142 ppm or 142 ppb H2S gas. The sensor provided a stable response reading at an average response time of 43±5 seconds, which was easily recovered after an average time of 99±5 seconds. The sensor response was highly repeatable and reversible with RSD values of 8.88%, and 8.60%, respectively. Compared with the performance of the conventional conducting polyaniline also doped with gold nanoparticles (PANI/AuNPs), the fabricated electroactive PI/AuNPs exhibited improved sensing performance making it a potential candidate in monitoring H2S in the environment and for work-related safety.
Sun, 3 November 2019
ARTICLE | doi:10.20944/preprints201911.0028.v1
Subject: Chemistry, Analytical Chemistry Keywords: gas sensor; hydrogen sensor; diode laser; TDLAS; WMS; absorption spectroscopy; laser spectroscopy; hydrogen
Online: 3 November 2019 (18:21:16 CET)
A laser-based hydrogen (H2) sensor using wavelength modulation spectroscopy (WMS) was developed for contactless measurements of molecular hydrogen. The sensor uses a distributed feedback (DFB) laser to target the H2 quadrupole absorption line at 2121.8 nm. The H2 absorption line exhibits weak collisional broadening and strong collisional narrowing effects. Both effects were investigated by comparing measurements of the absorption linewidth with detailed models using different line profiles that include collisional narrowing effects. The collisional broadening and narrowing parameters were determined for pure hydrogen as well as for hydrogen in nitrogen and air. Performance of the sensor was evaluated and the sensor applicability for H2 measurements in a range of 0- 10 %v of H2 was demonstrated. A precision of 0.02 %v was achieved with 1 meter of absorption pathlength (0.02 %v∙m) and 1 s of integration time. For the optimum averaging time of 20 s a precision of 0.005 %v∙m was achieved. A good linear relationship between H2 concentration and the sensor response was observed. A simple and robust transmitter-receiver configuration of the sensor allows in-situ installations in harsh industrial environments.
Wed, 25 September 2019
ARTICLE | doi:10.20944/preprints201909.0281.v1
Subject: Chemistry, Analytical Chemistry Keywords: polymer-derived contaminants; pvc fires; fire emissions analysis; polymer leachate characterization; gc-ms and ftir analysis of gaseous pollutants
Online: 25 September 2019 (09:12:03 CEST)
In order to assess the human exposure risks from the release of contaminants from water pipes made of polyvinyl chloride (PVC), experiments were carried out by subjecting the PVC pipe material to burning and leaching conditions followed by analysis of the emission and leachate samples. The emissions of burning pipes were analyzed by both infrared spectrometry and gas chromatography-mass spectrometry (GC-MS). The emission results indicate the presence of chlorinated components including chlorine dioxide, methyl chloride, methylene chloride, allyl chloride, vinyl chloride, ethyl chloride, 1-chlorobutane, tetrachloroethylene, chlorobenzene, and hydrogen chloride were detected in the emissions of burning PVC pipes. Furthermore, the concentrations of benzene, 1,3-butadiene, methyl methacrylate, carbon monoxide, acrolein, and formaldehyde were found at levels capable of affecting human health adversely. The analysis of PVC pipe leachates using GC-MS shows that there are 40-60 tentatively identified compounds, mostly long-chain hydrocarbons such as tetradecane, hexadecane, octadecane, and docosane, were released when the burned PVC materials were soaked in deionized water for one week. Quantitative analysis shows that 2-butoxyethanol, 2-ethyl-1-hexanol, and diethyl phthalate were found in the burned PVC polymer at the average levels of 2.7, 14.0, and 3.1 micrograms per gram (g/g) of pipe material. This study has significant implications for understanding the benzene contamination of drinking water in the aftermath of wildfires that burned polymer pipes in California.
Wed, 18 September 2019
ARTICLE | doi:10.20944/preprints201909.0213.v1
Subject: Chemistry, Analytical Chemistry Keywords: chlorogenic acid; extraction; coffee silverskin; analytical method
Online: 18 September 2019 (17:21:05 CEST)
Chlorogenic acid or 5-Caffeoylquinic acid is a polyphenolic component present in coffee and its by-products. Chlorogenic acid has been shown to exert biological properties, particularly in relation to glucose and lipid metabolism, including antibacterial, antioxidant, anti-inflammatory activities, among others. Due to its importance, it is necessary to evaluate the reliability of the analytical method for its determination in complex matrices such as food. In this work, different methods of chlorogenic acid extraction in coffee Silverskin were studied, as well as its quantification by HPLC. The results showed that the method of extraction with a mixture of methanol:water (3:1 v/v) in an ultrasonic bath, favored the recovery of chlorogenic acid with a recovery of 77.44%. The instrument detection limit for chlorogenic acid was 3.311 µg/mL and the quantification limit was 11.037 µg/mL. For coffee Silverskin, the concentration obtained of chlorogenic acid by the three extraction methods evaluated was in the range of 57 to 224 mg/kg of coffee silverskin (dry basis).
Mon, 9 September 2019
ARTICLE | doi:10.20944/preprints201909.0093.v1
Subject: Chemistry, Analytical Chemistry Keywords: reduced graphene oxide nanosheets; gold nanoparticles; composite materials; glucose oxidase; direct electron transfer
Online: 9 September 2019 (08:14:26 CEST)
Graphene-based composites have been widely explored for electrode and electrocatalyst materials for electrochemical energy systems. In this paper, a novel composite material of the reduced graphene oxide nanosheets (rGON) with gold nanoparticles (NPs) (rGON-AuNP) is synthesized, and its morphology, structure and composition are characterized by SEM, HRTEM, XRD, EDX, FTIR, Raman, and UV-Vis techniques. To confirm this material’s electrochemical activity, a glucose oxidase (GOD) is chosen as the target reagent to modify the rGON-AuNP layer to form GOD/rGON-AuNP/glassy carbon (GC) electrode. Two pairs of distinguishable redox peaks, corresponding to the redox processes of two different conformational GOD on AuNP, are observed on the cyclic voltammograms of GOD/rGON-AuNP/GC electrode. Both cyclic voltammetry and electrochemical impedance spectroscopy are employed to study the mechanism of direct electron transfer from GOD to GC electrode on the rGON-AuNP layer. In addition, this GOD/rGON-AuNP/GC electrode shows catalytic activity toward glucose oxidation reaction.
Mon, 2 September 2019
REVIEW | doi:10.20944/preprints201909.0020.v1
Subject: Chemistry, Analytical Chemistry Keywords: chemical pollutants; chemometrics; constructed wetlands; hydroponics; macrophytes; models; toxicity; water pollution
Online: 2 September 2019 (09:45:46 CEST)
Heavy metals and organic pollutants are ubiquitous environmental pollutants affecting the quality of soil, water and air. Over the past 5 decades, many strategies have been developed for the remediation of polluted water. Strategies involving aquatic plant use are preferable to conventional methods. In this study, an attempt was made to provide a brief review on recent progresses in research and practical applications of phytoremediation for water resources with the following objectives: (1) to discuss the toxicity of toxic chemicals pollution in water to plant, animals and human health (2) to summarise the physicochemical factors affecting removal of toxic chemicals such as heavy metals and organic contaminants in aqueous solutions by aquatic plants; (3) to summarise and compare the removal rates of heavy metals and organic contaminants in aqueous solutions by diverse aquatic plants; and (4) to summarise chemometric models for testing aquatic plant performance. More than 20 aquatic plants specie have been used extensively while duckweed (L. minor), water hyacinth (Eichhornia crassipes), water lettuce (P. stratiotes) are the most common. Overall, chemometrics for performance assessment reported include: Growth rate (GR), Growth rate inhibition (% Inhibition), Metal uptake (MU), translocation/transfer factor (TF), bioconcentration factor (BCF), Percent metal uptake (% MU), Removal capacity (RC) and Tolerance index (TI) while absorption rate have been studied using the sorption kinetics and isotherms models such as pseudo-first-order (PFO), pseudo-second-order (PSO), Freundlich, Langmuir and Temkin. Using modeling and interpretation of adsorption isotherms for performance assessment is particularly good and increases level of accuracy obtained from adsorption processes of contaminant on plant. Conclusion was drawn by highlighting the gap in knowledge and suggesting key future areas of research for scientists and policymakers.
ARTICLE | doi:10.20944/preprints201909.0017.v1
Subject: Chemistry, Analytical Chemistry Keywords: LC-MS; mesenchymal stem cells; stromal cells; fat differentiation; lipidomics; metabolomics; proteomics; multiomics; network analysis; mathematical modelling
Online: 2 September 2019 (06:07:17 CEST)
The molecular study of fat cell development in the human body is essential for our understanding of obesity and related diseases. Mesenchymal stem/stromal cells (MSC) are the ideal source to study fat formation as they are the progenitors of adipocytes. In this work, we used human MSCs, received from surgery waste, and differentiate them into fat adipocytes. The combination of several layers of information coming from lipidomics, metabolomics and proteomics enabled comprehensive analysis of the biochemical pathways in adipogenesis. Simultaneous analysis of metabolites, lipids and proteins in cell culture is challenging due to the compound’s chemical difference so that most studies involve separate analysis with unimolecular strategies. In this study, we employed a multimolecular approach using a two–phase extraction to monitor the crosstalk between lipid metabolism and protein-based signaling in a single sample (~105 cells). We developed an innovative analytical workflow including standardization with in-house produced 13C-isotopically labeled compounds, hyphenated high-end mass spectrometry (high-resolution Orbitrap MS) and chromatography (HILIC, RP) for simultaneous untargeted screening and targeted quantification. Metabolite and lipid concentrations ranged over 3-4 orders of magnitude and were detected down to the low fmol (absolute on column) level. Biological validation and data interpretation of the multiomics workflow was performed based on proteomics network reconstruction, metabolic modelling (MetaboAnalyst 4.0) and pathway analysis (OmicsNet). Comparing MSCs and adipocytes, we observed significant regulation of different metabolites and lipids such as triglycerides, gangliosides and carnitine with 113 fully reprogrammed pathways. The observed changes are in accordance with literature findings dealing with adipogenic differentiation of MSC. These results are a proof of principle for the power of multimolecular extraction combined with orthogonal LC-MS assays and network construction. Considering the analytical and biological validation performed in this study, we conclude that the proposed multiomics workflow is ideally suited for comprehensive follow-up studies on adipogenesis and is fit for purpose for different applications.
Fri, 30 August 2019
REVIEW | doi:10.20944/preprints201908.0316.v1
Subject: Chemistry, Analytical Chemistry Keywords: air pollution; dermal route; fibers; health risk; inhalation; micropollutants
Online: 30 August 2019 (05:08:43 CEST)
Microplastics (of size < 5mm) pollution in our environment is of current concern by researchers, public media and non-governmental organizations. Implications by their presence in aquatic and soil ecosystems have been well studied and documented, but less attention has been paid on airborne microplastics (MPs). Studies concerning airborne microplastics started from 2016 and only a few (n=7) have been published till date. Although, studies may increase in the following years, since air is very important for human survival. Microplastics have been observed in atmospheric fallouts in indoor and outdoor environments using a sampling or vacuum pump, rain sampler and/or particulate fallout collector. Identification and quantification have been carried out by visual, spectroscopic and spectrometric techniques. Factors such as meterological, climatic and anthropogenic influence the distribution and movement of airborne MP. Human exposure may be through inhalation or dermal route with their potential biopersistence and translocation. Ingestion may cause localized inflammation and cancer due to responses by the immune cells, especially in individuals with compromised metabolism and poor clearance mechanisms. Ecological risks involve possible contamination of the ecosystem through a dynamic relationship of MPs in soil, water and air forming a MP contamination cycle. The present review aimed at providing a comprehensive overview of current knowledge or information regarding microplastics in air, identifies gap in knowledge and give suggestions for future research.
Mon, 26 August 2019
REVIEW | doi:10.20944/preprints201908.0260.v1
Subject: Chemistry, Analytical Chemistry Keywords: air pollution; micropollutants; plastic debris; risks; soil pollution; toxicity; water pollution
Online: 26 August 2019 (01:39:10 CEST)
Current problem facing researchers globally is microplastics as well as toxic chemical pollution of the ecosystem. Microplastics carry toxic chemicals in the ecosystem.serving as a vector for transport. In this study, a review of the literature has been conducted with the following objectives: (1) to summarise the concentrations of toxic chemicals such heavy metals and hydrophobic organic contaminants sorped on microplastics; (2) to evaluate their spatial distribution regarding adsorbed contaminant (3) to discuss plausible mechanism by which microplastics adsorp or desorp toxic chemicals in the environment; (4) to discuss implications of their occurrence in air, water and soil media; and (5) to discuss the impact of ingested microplastics to human health. Microplastics are ubiquitous environmental contaminant. Concentrations of sorped toxic chemical varied with location which represents a local problem; industrialized areas (especially areas experiencing crude oil related activities or have history of crude oil pollution) have higher concentrations than less industrialized areas. Ingestion of microplastics has been demonstrated in a range of marine and soil organisms as well as edible plants, thus possible contaminating the base of the food-web. Potential health effect to human is by particle localization, chemical toxicity and microbal toxins. We conclude by highlighting the gap in knowledge and suggesting key future areas of research for scientists and policymakers.
Mon, 12 August 2019
ARTICLE | doi:10.20944/preprints201908.0145.v1
Subject: Chemistry, Analytical Chemistry Keywords: authentication of perfume, flavours, nuclear magnetic resonance, PCA
Online: 12 August 2019 (14:00:37 CEST)
The industry of the counterfeit goods is one of the largest underground business in the world and it is rapidly growing. Counterfeits can lead not only to loss of profit for honest producers but also have a negative impact on consumers who receive poor quality goods at an excessive price and may be exposed to health damages and safety issues. Perfume industry is constantly exposed to the problem of counterfeits with the fast developing parallel market of inspired perfumes being an important issue. It prompts for the identification of methods that classify the quality of this type of products. In this paper the application of proton nuclear magnetic resonance spectroscopy is employed for the authentication of perfumery products for the first time. Molecular composition of several types of authentic brand fragrances for women were compared with their cheaper inspired equivalents and fake products. Our approach offers the prospect of a fast and simple method for discrimination and counterfeit detection of perfumes using 1H NMR spectroscopy.
Mon, 5 August 2019
Subject: Chemistry, Analytical Chemistry Keywords: screen printed electrodes; Ag nanoparticles; drop-casting; spin-coating; nanoprisms; heavy metals; Differential pulse anodic stripping voltammetric; electrocatalysis
Online: 5 August 2019 (04:55:05 CEST)
The screen-printed carbon nanofibers electrodes (SPCNFE) represent an alternative with great acceptance due to their results, as well as their low impact for the environment. In order to improve their performance, in the present work they were modified with silver nanoparticles (Ag-NPs) and electrochemically characterized by using anodic stripping voltammetry. From the Ag-NPs synthesis, silver seeds (Ag-NS) and silver nanoprisms (Ag-NPr) were obtained. The Ag-NPs formation was confirmed by micrographs where Ag-NPs with diameters of 12.20±0.04 nm for Ag-NS, and 20.40±0.09 nm for Ag-NPr were observed. The electrodes were modified by using three different deposition methods: drop-casting, spin-coating and in-situ approaches. It was observed that the last methodology showed a low amount of Ag-NS deposited on the electrode surface and a deep alteration of this surface. Those facts suggested that the in situ synthesis methodology were not appropriate for the determination of heavy metals and it was discarded. The incorporation of the nanoparticles by spin-coating and drop-casting strategies showed different spatial distribution on the electrode surface as proved by scanning electron microscopy. The electrodes modified by these strategies, were evaluated for the cadmium(II) and lead(II) detection using differential pulse anodic stripping voltammetry, obtaining detection limit values of 2.1 and 2.8 µg L-1, respectively. The overall results showed that the incorporation route does not change directly the electrocatalytic effect of the nanoparticles, but the shape of these nanoparticles (spherical for seeds and triangular for prisms) has a preferential electrocatalytical enhancement over Cd(II) or Pb(II).
Tue, 23 July 2019
ARTICLE | doi:10.20944/preprints201907.0263.v1
Subject: Chemistry, Analytical Chemistry Keywords: ambient ionization; mass spectrometry; high-throughput sampling; imaging; modular robot; open hardware; lab automation; peer production; open software; low-temperature plasma
Online: 23 July 2019 (15:20:38 CEST)
Abstract: Mass spectrometry research laboratories reported multiple probes for ambient ionization in the last years. Combining them with a mechanical moving stage enables automated sampling and imaging applications. We developed a robotic platform, which is based on RepRap 3D-printer components, and therefore easy to reproduce and to adopt for custom prototypes. The minimal step width of the Open LabBot is 12.5 μm, and the sampling dimensions (x, y, z) are 18 × 15 × 20 cm. Adjustable rails in an aluminium frame construction facilitate the mounting of additional parts such as sensors, probes, or optical components. The Open LabBot uses industry-standard G-code for its control. The simple syntax facilitates the programming of the movement. We developed two programs: 1) LABI-Imaging, for direct control via a USB connection and the synchronization with MS data acquisition. 2) RmsiGUI, which integrates all steps of mass spectrometry imaging: The creation of G-code for robot control, the assembly of imzML files from raw data and the analysis of imzML files. We proved the functionality of the system by the automated sampling and classification of essential oils with a PlasmaChip probe. Further, we performed an ambient ionization mass spectrometry imaging (AIMSI) experiment of a lime slice with laser desorption low-temperature plasma (LD-LTP) ionization, demonstrating the integration of the complete workflow in RmsiGUI. The design of the Open LabBot and the software are released under open licenses to promote their use and adoption in the instrument developers’ community.
Mon, 22 July 2019
ARTICLE | doi:10.20944/preprints201907.0235.v1
Online: 22 July 2019 (08:13:57 CEST)
In this work, the capabilities of a novel miniaturized and portable MicroNIR spectrometer were investigated in order to propose a practical and intelligible test allowing the rapid and easy screening of cannabinoids in hemp flour. In order to develop a predictive model able to identify and simultaneously to quantify the residual amount of cannabinoids, specimens from flours commercially available on the markets were considered and spiked with increasing amount of Cannabidiol (CBD), Δ9-Tetrahydrocannabinol (THC) and Cannabigerol (CBG). Partial Least Square-Discriminant Analysis (PLS-DA) and Partial Least Square regression (PLSr) were applied for the simultaneously detection and quantification of cannabinoids. Results demonstrated that MicroNIR/Chemometric platform is statistically able to identify the presence of CBD, THC and CBG in simulated samples containing cannabinoids from 0.001 to 0.1 %ww, with the accuracy and sensitivity of the reference official methods actually proposed. The method was checked against false positive and true positive response and results proved to be those required for confirmatory analyses; permitting to provide a fast and accurate method for the monitoring of cannabinoids in hemp flours.
Thu, 11 July 2019
ARTICLE | doi:10.20944/preprints201907.0157.v1
Subject: Chemistry, Analytical Chemistry Keywords: acrylamide; biscuits; mitigation measures; benchmark levels; contaminant
Online: 11 July 2019 (11:05:40 CEST)
Acrylamide (AA), a molecule which potentially increases the risk of developing cancer, is easily formed in food rich in carbohydrates, such as biscuits, wafers and breakfast cereals, at temperatures above 120 °C. Thus, it is eminent the need to detect and quantify the AA content in processed foodstuffs, in order to delineate the limits and mitigation strategies. This work reports the development and validation of a high-resolution mass spectrometry-based methodology for identification and quantification of AA in specific food matrices of biscuits, by using LC-MSn with electrospray ionization and Orbitrap as mass analyser. The developed analytical method showed good repeatability (RSDr 11.1%) and 3.55 μg kg-1 and 11.8 μg kg-1 as limit of detection (LOD) and limit of quantification (LOQ), respectively. The choice of multiplexed targeted-SIM mode (t-SIM) for AA and AA-d3 isolated ions provided enhanced detection sensitivity, as demonstrated in this work. Results for AA concentration obtained vary between 323.7 and 2056.1 μg kg-1. During baking an increase in AA concentration was observed, as well as between samples taken from different areas of the baking oven. Statistical processing of data was performed in order to compare the AA levels with several production parameters, such as time/cooking temperature, placement on the cooking conveyor belt, color and moisture for different biscuits. The composition of the raw materials was statistically the most correlated factor with the AA content when all samples are considered. The statistical treatment presented herein enables an important prediction of factors influencing AA formation in biscuits contributing for putting in place effective mitigation strategies.
Tue, 11 June 2019
ARTICLE | doi:10.20944/preprints201906.0088.v1
Subject: Chemistry, Analytical Chemistry Keywords: ricin; marker peptides; unambiguous identification; mass spectrometry
Online: 11 June 2019 (08:27:32 CEST)
Both ricin and R. communis agglutinin (RCA120), belonging to the type II ribosome-inactivating proteins (RIPs-Ⅱ), are derived from the seeds of castor bean plant. They share very similar amino acid sequences, but ricin is much more toxic than RCA120. It is urgently necessary to distinguish ricin and RCA120 in response to public safety. Currently, mass spectrometric assays are well established for unambiguous identification of ricin by accurate analysis of differentiated amino acid residues after trypsin digestion. However, diagnostic peptides are relatively limited for unambiguous identification of trace ricin, especially in complex matrices. Here, we demonstrate a digestion strategy of multiple proteinases to produce novel peptide markers for unambiguous identification of ricin. LC-HRMS was used to verified the resulting peptides, among which only the peptides with uniqueness and good MS response were selected as peptide markers. Seven novel peptide markers were obtained from tandem digestion of trypsin and endoproteinase Glu-C in PBS buffer. From the chymotrypsin digestion under reduction and non-reduction conditions, eight and seven novel peptides were selected respectively. Using pepsin under pH 1~2 and proteinase K digestion, 6 and 5 peptides were selected as novel peptide markers. In conclusion, the obtained novel peptides from the established digestion methods can be recommended for the unambiguous identification of ricin during the investigation of illegal use of the toxin.
Fri, 7 June 2019
ARTICLE | doi:10.20944/preprints201906.0061.v1
Subject: Chemistry, Analytical Chemistry Keywords: new, sulbatamol sulphate, membrane electrode , utilizing for determination
Online: 7 June 2019 (13:49:13 CEST)
A new sulbatamol sulphate SBS membrane electrode was prepared that utilizing for its determination ; depend on the forming of the association complex ion of sulbatamol sulphate by the phosphotungstate counter anion deposed in poly vinyl chloride PVC polymer, by use a (Di-n- Octyl Phenyl Phthalate)(Dopp) as the plastizier substance, in membrane.The features properties as well as the behavior of it .The new electrode have been elaborated. The concentrations of medicine by utillizing This sensor show a fast, stable, near-Nernstian response in the range (1x10-1-1x10-6) mol/ L were determined with correlation coefficient of about (r = 0.9991) and with of a relative standard about 0.416 additionally deviation relative standard error of 1.710 %.pot The nernast linearity slop was founded and it is equal to 28.9 mV/decade and the detection limit was 4.1 x 10-6 mol/ L.The electrode selectivity coefficient Ki,j was calculated, in the existence of several interferences cations with confirmed medicine solutions. It was found the pH range response is in the range of (3 -7), with the response time of (30 – 116) sec. for various concentrations at room temperture , the lifetime for electrode was found to be more than 21 days. The electrode was successfully used for potentiometric limitation of sulbatamol sulphate in several pharmaceutical drugs by using direct potentiometry.
Fri, 31 May 2019
ARTICLE | doi:10.20944/preprints201905.0376.v1
Subject: Chemistry, Analytical Chemistry Keywords: alizarin; Austria; dyes; forgery; FORS; inks; madder; manuscripts; orchil; SERS
Online: 31 May 2019 (08:25:27 CEST)
The Privilegium maius is one of the most famous and spectacular forgeries in medieval Europe. It is a set of charters made in 14th century upon commitment by duke Rudolf IV, a member of the Habsburg family, to elevate the rank and the prestige of his family. These five charters, now kept at the Österreichisches Staatsarchiv in Vienna, have been subjected to a thorough interdisciplinary study in order to shed light on its controversial story. The charters are composed by pergamenaceous documents bound to wax seals with coloured textile threads. The present contribution concerns the characterisation of the inks used for writing and of the dyes used to colour to the threads: are they compatible with the presumed age of the charters? Though showing only a part of the whole story of the charters, dyes analysis could contribute in assessing their complex history from manufacturing to nowadays. The dyes were characterised with non-invasive in situ measurements by means of FORS and with micro-invasive measurements by means of SERS and HPLC-MS analysis. The results showed that the threads of four of the charters (three dyed with madder, one with orchil) were apparently coloured at different dyeing stages, then re-dyed in the 19th-20th century.
Wed, 15 May 2019
ARTICLE | doi:10.20944/preprints201905.0189.v1
Subject: Chemistry, Analytical Chemistry Keywords: exhaled breath analysis; field-asymmetric ion mobility spectrometry; FAIMS; Fourier-transform infrared spectroscopy; FTIR; luminescence sensing; infrared sensors; hyphenated techniques; hybrid techniques; acetone; carbon dioxide; oxygen
Online: 15 May 2019 (10:49:38 CEST)
The reliable online analysis of volatile compounds in exhaled breath remains a challenge as a plethora of molecules occur in different concentration ranges (i.e. ppt to %), and need to be detected against an extremely complex background matrix. While this complexity is commonly addressed by hyphenating a specific analytical technique with appropriate preconcentration and/or preseparation strategies prior to detection, we herein propose the combination of three analytical tools based on truly orthogonal measurement principles as an alternative solution: field-asymmetric ion mobility spectrometry (FAIMS), Fourier-transform infrared (FTIR) spectroscopy-based sensors utilizing substrate-integrated hollow waveguides (iHWG), and luminescence sensing (LS). These three tools have been integrated into a single compact analytical platform suitable for online exhaled breath analysis. The analytical performance of this prototype system was tested via artificial breath samples containing nitrogen (N2), oxygen (O2), carbon dioxide (CO2) and acetone as a model volatile organic compound (VOC) commonly present and detected in breath. Functionality of the combined system was demonstrated by detecting these analytes in their respectively breath-relevant concentration range and mutually independent of each other generating orthogonal yet correlated analytical signals. Finally, adaptation of the system towards the analysis of real breath samples during future studies is discussed.
Fri, 10 May 2019
Subject: Chemistry, Analytical Chemistry Keywords: BiVO4; nanobelts; photocatalyst; reusability; stability
Online: 10 May 2019 (14:33:25 CEST)
BiVO4 powder was synthesized by a simple hydrothermal method. The nanobelts with well dispersed and uniform morphology were synthesized by controlling the temperature. The structure of BiVO4 powder was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The diameter of the nanobelts was about 50 nm. The structure and composition of the nanobelts were studied by X-ray diffraction (XRD), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). The absorption intensity of BiVO4 powder in UV-Vis region was compared by UV–vis diffuse reflectance spectroscopy. As a photocatalyst, BiVO4 nanobelts have good photocatalytic ability under visible light irradiation, which is very useful for the treatment of environmental wastewater. The synthesized nanobelts photocatalyst can be reused without destroying its structure. The reusability and chemical stability of photocatalysts are of great significance for practical application.
Mon, 6 May 2019
Subject: Chemistry, Analytical Chemistry Keywords: stable-isotope dimethyl labeling; liquid chromatography-tandem mass spectrometry; food allergen; kiwifruit
Online: 6 May 2019 (07:57:06 CEST)
Stable-isotope dimethyl labeling is a highly reactive and cost-effective derivatization procedure that could be utilized in proteomics analysis. In this study, a liquid chromatography-tandem mass spectrometry in multiple reaction monitoring mode (LC-MS-MRM) platform for the quantification of kiwi allergens was first developed using this strategy. Three signature peptides for target allergens Act d 1, Act d 5, and Act d 11 were determined and were derivatized with normal and deuterated formaldehyde as external calibrants and internal standards, respectively. The results showed that sample preparation with the phenol method provided comprehensive protein populations. Recoveries at four different levels ranging from 72.5–109.3% were achieved for the H-labeled signature peptides of Act d 1 (SPA1-H) and Act d 5 (SPA5-H) with precision ranging from 1.86–9.92%. The limit of quantification (LOQ) was set at 8 pg mL–1 for SPA1-H and at 4 ng mL–1 for SPA5-H. The developed procedure was utilized to analyze seven kinds of hand-made kiwi foods containing 0.0175–0.0515 mg g–1 of Act d 1 and 0.0252–0.0556 mg g–1 of Act d 5. This study extended the applicability of stable-isotope dimethyl labeling to the economical and precise determination of food allergens and peptides.
Tue, 23 April 2019
ARTICLE | doi:10.20944/preprints201901.0321.v2
Subject: Chemistry, Analytical Chemistry Keywords: SPME; Carboxen; volatile organic compounds; benzene; transport in porous media; COMSOL Multiphysics
Online: 23 April 2019 (06:24:45 CEST)
Experimental optimization of analytical methods based on solid-phase microextraction (SPME) is a complex and labor-intensive process associated with uncertainties. Using the theoretical basics of SPME and finite element analysis software for the optimization proved to be an efficient alternative. In this study, an improved finite element analysis-based model for SPME of volatile organic compounds (VOCs) by porous coatings was developed mainly focussing on the mass transport in coatings. Benzene and the Carboxen/polydimethylsiloxane (Car/PDMS) coating were used as the model VOC and a porous SPME coating, respectively. It has been established that in the coating, volumetric fractions of Carboxen, PDMS, and air are 33, 42 and 24%, respectively. Knudsen diffusion in micropores can slow down a mass transport of analytes in the coating. When PDMS was considered as the solid part of the coating, lower root-mean-square deviation of the modeling results from experimental data was observed. It has been shown that the developed model can be used to model the extraction of VOCs from air and water samples encountered in a typical SPME development method procedure. It was possible to determine system equilibration times and use them to optimize sample volume and Henry’s law constant. The developed model is relatively simple, fast, and can be recommended for optimization of extraction parameters for other analytes and SPME coatings. The diffusivity of analytes in a coating is an important property needed for improved characterization of existing and new SPME polymers and analytical method optimization.
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