Sensing of sulfhydryl based compounds by a simple electrochemical approach

Abstract We report a simple and effective electrochemical approach to determine thiolic compounds based on the reaction of sulfhydryl group with o -benzoquinone, which was freshly prepared by enzymatic oxidation of catechol in the presence of tyrosinase. The electrochemical reduction of o -benzoquinone was used as detection method by performing differential measurements in the absence and in the presence of thiols on glassy carbon electrode. Four thiols, thiocholine, cysteine, captopril and cysteamine were tested. Spectrometric measurements showed that reaction between thiols and o -benzoquinone is fast and complete. Therefore, indirect detection of thiols could be realized amperometrically by monitoring the decrease of the reduction current of the o -benzoquinone. A sensitivity of 76 and 177 μA/mM cm 2 was achieved for thiocholine and cysteine, respectively. Estimation of the total content of the compounds with sulfhydryl groups could be realized from samples containing thiols by using thiocholine or cysteine as reference compound. The proposed electrochemical approach could be used for selective detection of thiols compounds in the presence of amines at neutral pH.