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This paper proposes a methodology based on electrochemical reduction for a fast, specific and sensitive determination of genistein by square-wave voltammetry (SWV). The highest peak currents and optimal definition of reduction peak of genistein was obtained by using a supporting electrolyte consisted of 0.04 mol L(-1) phosphate buffer-methanol (8:2, v/v) solution at pH 7.5 and cationic surfactant 2.21 x 10(-4) mol L(-1) cetyltrimethylammonium bromide (CTAB). The peak current was proportional to the concentration of genistein in the range 1.14 x 10(-7) to 1.09 x 10(-6) mol L(-1), with a detection limit and quantification of 3.43 x 10(-8) mol L(-1) and 1.14 x 10(-7) mol L(-1), respectively. The extraction procedure was evaluated for a better determination of genistein contained in soy flour and soy based supplements. The efficiency of the proposed methodology was demonstrated by comparing the results obtained by SWV with those obtained by the high-performance liquid chromatography (HPLC) method.

This paper proposes a methodology based on electrochemical reduction for the simultaneous determination of three sunscreen agents, namely 4-methylbenzylidene camphor (MBC), benzophenone-3 (BENZO) and 2-ethylhexyl-4-methoxycinnamate (EHMC) by differential-pulse polarography (DPP). The highest peak currents and optimal separation of reduction peaks were obtained by using a supporting electrolyte consisted of Britton-Robinson buffer-methanol (8:2) solution at pH 4.0 and cationic surfactant 3.0 x 10(-4)mol L(-1) cetyltrimethylammonium bromide (CTAB). The methodology was validated using four commercial sunscreen preparation as a sample and the results showed high recovery rates. The efficiency of the proposed methodology was demonstrated by comparing the results obtained by DPP with those obtained by the high-performance liquid chromatography (HPLC) method.