Electrochemical determination of hydroquinone in cosmetics by cyclic voltammetry using glassy carbon electrode

College

College of Science

Department/Unit

Chemistry

Document Type

Archival Material/Manuscript

Publication Date

2005

Abstract

The electrochemical behaviour of hydroquinone in aqueous solution was studied by cyclic voltammetry using glassy carbon electrode to optimize a method for its determination as an active ingredient in cosmetic preparations. The effect of supporting electrolyte (0.1M KCI, KNO3, H2SO4, and phosphate buffer), pH (2.0, 4.5, 7.0, 9.5, 12.0) and scan rate (25, 50, 80, 100 mV/s) were studied. An increase in current was observed at increasing rate for all electrolytes suggesting a diffusion-controlled transport of electroactive species. In basic medium, the rate of reduction was faster, while the rate of oxidation is slower. The reverse was true in acidic medium. Hydroquinone exhibited better response using phosphate buffer (pH = 9.5) at a scan rate of 100mV/s making it suitable for analysis. The voltammogram observed was quasi-reversible with two distinct peaks. Cathodic peak was used for the analysis. The detection limit was 0.1 µM with a linear range of 1.0 x 10 to 1.0 x 10M of HQ. Both the standard calibration and standard addition methods could be employed for the analyses of the samples. The analyses of three commercially available skin whiteners/exfoliants in liquid preparations gave % recovery range of 98.13 104.6%. The spiked placebo method was used to determine the accuracy of the method in the analysis of cream sample. This was conducted by combining 5.0 g sepigel (cream base) and known amount of hydroquinone. The standard addition method gave 96.81% recovery. In all the analyses, the %RSD was below 2.90%. Results of ten repetitive measurements showed 0.273% RSD.. The method exhibits excellent stability, reproducibility, immediate response, and can be used to quantify hydroquinone in other cosmetic preparations.

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Disciplines

Chemistry

Keywords

Hydroquinone—Analysis; Electrochemical analysis

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