Simultaneous determination of captopril and thioguanine in pharmaceutical compounds and blood using cathodic adsorptive stripping voltammetry

A reliable, highly selective and sensitive procedure is presented for simultaneous determination of captopril and thioguanine based on cathodic adsorptive stripping of Cu(I)-captopril and Cu(I)-thioguanine complexes on a hanging mercury drop electrode. Captopril and thioguanine were preconcentrated onto the surface of hanging mercury drop electrode using Cu(II) as a suitable probe, with accumulation time of 90 s. Then the preconcentrated complexes were analyzed by cathodic stripping differential pulse voltammetry. The effect of various parameters such as pH, concentration of copper, accumulation potential, accumulation time and scan rate on the sensitivity were studied. The optimum conditions for simultaneous determination of captopril and thioguanine include pH=3.5, 45.0 ng mL-1 copper(II) concentration, accumulation potential of -0.10 V and scan rate of 60 mV s-1. Under the optimum conditions and for an accumulation time of 90 s, the measured peak currents at about -0.15 V and -0.40 V (vs. Ag/AgCl) are proportional to the concentrations of thioguanine and captopril over the ranges of 0.15-180 and 0.5-100 nmol L-1, respectively. The limits of detection are 0.08 and 0.3 nmol L-1 for thioguanine and captopril, respectively. The relative standard deviations for five replicate analyses of 20.0 nmol L-1 captopril and thioguanine are 2.5% and 2.1%, respectively. The method was applied to the determination of captopril and thioguanine in synthetic mixed samples, pharmaceutical samples and human serum with satisfactory results

The Roles of Alkyl Branches of Ionic Liquid in the Corrosion Resistance of Pb/Sb/Sn Grids Alloy in Lead-Acid Battery

This paper describes the effects of ionic liquids (ILs) including mono, bicyclohexyl, and tetrahexyl ammonium hydrogen sulphate on the corrosion behaviour of Pb/Sb/Sn grids alloy of lead-acid battery with Pb, Sb (1.66 wt%), and Sn (0.24 wt%). Electrochemical behaviour has been investigated using Tafel plots and electrochemical impedance spectroscopy with various concentrations of ILs as electrolyte additives in 4.0 mol⋅L-1 sulphuric acid. The obtained results indicated that, by increasing number of alkyl or cycloalkyl branches in ILs, the corrosion rate of the lead alloy decreases, whereas inhibition efficiency shows a reverse effect. In the presence of all ILs in different concentrations, conversion current of PbSO4 to PbO2 (ia and ic) increases, while the reversibility, deduced from peak potential differences, decreases. Also, the effect of ILs adsorption model on the corrosion behaviour of electrode was proposed