Octyl methoxycinnamate (OMC) is a common UVA and UVB filter molecule that is widely used is commercial sunscreens. Here, we use gas-phase laser photodissociation spectroscopy to characterize the intrinsic photostability and photodegration products of OMC, by studying the system as its protonated form, i.e. [OMC·H]+. The major photofragments observed have, m/z 179, 161, and 133, corresponding to fragmentation on either side of the of the ether oxygen of the ester group (m/z 179, and 161) or the C-C bond adjacent to the ester carbonyl group. Additional measurements were obtained using higher-energy collisional dissociation mass spectrometry (HCD-MS), to identify fragments which result from breakdown of the vibrationally hot electronic ground state. We found that the m/z 179 and 161 ions are the main fragments produced by this route. Notably, the m/z 133 ion was not observed through HCD-MS, revealing that this product ion is only produced through a photochemical route. Our results demonstrate that UV photoexcitation of OMC is able to access a dissociative excited state surface that uniquely leads to rupture of the C-C bond adjacent to the key ester carbonyl group.

Sunscreens are topical preparations containing one or more compounds that protect humans from ultraviolet (UV) light. This review focuses on analytical methods, particularly liquid chromatography, aimed at identifying and determining UV filters (UVFs) in environmental and marine biota matrices. A literature review was done using NIH (PubMed and Medline), FDA and EPA databases, Google Scholar, and Federal Regulations. This retrospective literature review is focused on the last five years. UVFs quantification in environmental and biological matrices showed a wide array of methods where liquid chromatography is predominant. The scientific literature identified a large variety of analytical methodologies that are compared in this review, to evaluate the better results in terms of limits of quantification and the possibility to identify as many analytes as possible simultaneously.