Determination of metallothionein at the femtomole level by constant current stripping chronopotentiometry

Metallothionein (MT) from rabbit liver was analyzed by differential pulse polarography, cyclic voltammetry, square wave voltammetry, and chronopotentiometric stripping analysis (CPSA) with a hanging mercury drop electrode under various conditions. The highest sensitivity of the AIT determination was obtained with CPSA which produced a well-developed peak H due to catalytic hydrogen evolution at highly negative potentials. The highest peak H was obtained in borate buffer close to pH 8.0. In this medium, subnanomolar concentrations of NIT were detectable. In the adsorptive transfer stripping (medium exchange) experiments, determination of few femtomoles of MT in 5-muL aliquots of the analyte was possible. CPSA determination of AIT in various tissues of carp (Cyprinus carpio) yielded values in agreement with the published data.