Development of a method for total plasma thiols measurement using a disposable screen-printed carbon, electrode coupled with a MnO2 reactor

We report here an electrochemical approach for total plasma thiols measurement using a disposable screen-printed carbon electrode coupled with a MnO2 reactor. In this approach, catechol is used as an electrochemical indicator to monitor the nucleophilic addition of thiols to the o-quinone. A reactor containing MnO2 particles is effectively combined into the flow injection analysis (FIA) system not only to facilitate the oxidation of catechol but also to eliminate the interference from ascorbic acid. At a low operating potential of -0.1 V versus Ag/AgCl, the interference by electroactive species (e.g., uric acid) and physiological constituents (e.g., lysine) can also be avoided. The analytical parameters in FIA for the determination of thiols (cysteine, homocysteine and glutathione) have been assessed. The proposed approach is finally validated through its application to the analysis of total thiols in human plasma. (c) 2007 Elsevier B.V. All rights reserved.