Cyclic voltammetry and quartz crystal microbalance electrochemical studieson thiosalicylic acid and dithiodibenzoic acid

Cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQ CM) were used to study the behavior of thiosalicylic acid (KTS) and dithiod ibenzois acid (DTDB) at the controlled-growth mercury drop electrode (CGMDE ), at the gold electrode, and at the carbon electrode. The CV method was us ed to study peak current intensities and peak potentials in relation to pH of the solution, to scan rate and to the concentration of the analyte. Opti mum measurement parameters were established and stock solutions developed. The electrode activity was found to be primarily due to the oxidation of th e sulhydryl group. The currents observed are diffusion controlled, Electroc hemical studies on complexes of KTS with Cu(II) were undertaken at varying constituent proportions and the cathodic peak was found to rise by ca. 70% whereby the sensitivity of the determination was considerably increased. Th e EQCM method allowed to establish that, as KTS is oxidized, the electrode slightly gains in weight (ca. 80 ng). As DTDB is reduced, the electrode sli ghtly looses in weight(ca40 ng). Studies on the equimolecular KTS-Cu(II) co mplex showed the electrode to gain about 125 ng more in weight than in the solutions containing KTS alone, a fact evidencing for the formation of the complex and for its deposition on the electrode surface. A procedure was de veloped to determine KTS and DTDB in the substance by the CV method Statist ical evaluation of data showed the results to be characterized by good accu racy and precision (RSD 0.80% and 0.61%, respectively).