Electrochemical Detection Of Cysteine In A Flow System Based On Reductive Desorption Of Thiols From Gold.

A simple strategy for cysteine determination using flow-injection analysis with electrochemical detection is described. The approach is based on the chemisorptions reactions of the sulfur moiety of cysteine upon polycrystalline gold electrodes and its subsequent reductive desorption. The electrochemical measurements were accomplished by the application of differential pulse voltammetry (DPV) for the operational optimization and pulsed electrochemical detection (PED) in combination with flow-injection analysis for the electrochemical detection as time function. The electroactive species could be adsorbed in a potential level (0.1 V versus SCE), at other (-0.6 V versus SCE) occurs their reductive desorption from the electrode, while the analytical current is recorded simultaneously, and a third potential step is applied to the complete regeneration of the gold electrode surface (-1.3 V versus SCE). The linear response range was observed between 1.0 x 10(-6) and 6.0 x 10(-6) mol L(-1) with a good reproducibility (R.S.D.