Catalytic hydrogen evolution in the presence of methylthiohydantoin–glycine and cobalt(II) ion: a study by cathodic stripping voltammetry at a hanging mercury drop electrode

• Published in: Talanta (Oxford) 1999-02, Vol.48 (2), p.491-494
• Main Authors: BANICA, F. G, SPATARU, N
• Format: Article
• Language: English
• Subjects: Amino acids; Analytical chemistry; Catalytic hydrogen current; Cathodic stripping voltammetry; Chemistry; Electrochemical methods; Exact sciences and technology; Thiohydantoin derivatives
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/S0039-9140(98)00259-8

The carbon–sulfur bond in methylthiohydantoin–glycine (MTH–Gly) is broken during the deposition on the mercury electrode at potentials around −0.1 V versus SCE, giving mercury sulfide which is detected by the characteristic cathodic peak at −0.7 V. If cobalt (II) is also present, the product of the deposition step is a mixture of mercury and cobalt sulfides. During the cathodic scan, the last one is reduced to a transient Co(0) species that catalyses the reduction of hydrogen ion to the hydrogen molecule by a mechanism alike to that emphasized for the Co(II)-sulfide ion system (F.G. Bănică, N. Spătaru, T. Spătaru, Electroanalysis 9 (1997) 1341). This electrode process induces a cathodic peak at −1.4 V that enables the determination of MTH–Gly down to 10 −7 M in the borax buffer at pH 8.5. The possible extension of this method to other classes of organic sulfur compounds is briefly discussed.