Electrochemical Behaviour of a Gold Film- Glassy Carbon Electrode for Determination of Chromium (VI)

A gold nanostructured film modified glassy carbon electrode (Au_film/GCE) was developed for the determination of chromium (VI) in water sample. GCE was immersed into HAuCl₄ solution (10^-3M) and electrodeposition of thin gold layer was conducted at –0.4 V (vs Ag/AgCl) for 10 min. The strong affinity between Au and Cr species resulted with increasing of Cr (VI) signal, compared with the bare glassy carbon electrode. The electrodepositing time, type of supporting electrolyte, pH, the scan rate, modulation amplitude, and modulation time were optimized using differential pulse anodic stripping voltammetry (DP-ASV). The calibration graph using accumulation time of 120 s was linear from 10 to 120 µgL^-1 with a sensitivity 1.3 x 10^-2 µA/µgL^-1. Under optimum experimental conditions, a good correlation coefficient R²=0.9971, and a low detection limit 5.5 µg/L Cr (VI) was obtained. The signal was reproducible with a relative standard deviation ±4.5 %. The developed Au_film/GCE sensor was applied for the Cr (VI) determination of in sewage water samples.