Comparison of indirect cathodic stripping voltammetric methods based on accumulation of mercury, copper(I) and nickel salts or complexes at a hanging mercury drop electrode : determination of 2-mercaptobenzot h iazole

摘要

A preliminary study of the indirect cathodic stripping udvoltammetric determination of 2-mercaptobenzothiazole ud(MBT) based on accumulation of its mercury, copper(1) udand nickel(I1) salts or complexes was made as part of a udwider study comparing these three related techniques of uddetermining thiols. Detection limits for MBT using the udcopper@) and nickel(I1) methods ( c 2 X udconsiderably lower than that for the mercury method ud(about 3 x lo-' moll-1). The mercury method is udsusceptible to interference from copper(I1) and large udamounts of nickel(@, and seems generally to be less udreliable for the determination of MBT. The change from udaccumulation as the mercury salt to accumulation as the udcopper(1) salt is illustrated in the presence of excess of udMBT over copper(@ with increasing copper(I1) udconcentrations, and with change of accumulation potential udto more negative values from +lo0 mV. In the presence of uda stoichiometric amount or excess of copper(I1) over MBT, udno mercury salt is accumulated at potentials more udnegative than +50 mV. Currents obtained for MBT with udthe nickel(I1) method are much higher than those obtained udpreviously with cysteine and penicillamine.