Constant current chronopotentiometric stripping analysis of Cd-metallothionein on carbon and mercury electrodes. Comparison with voltammetry

Constant current chronopotentiometric shipping analysis (CPSA) on hanging m ercury drop electrode, using positive or negative stripping current, reveal ed similar behavior of cadmium metallothionein (CdMT) as observed with volt ammetry but higher sensitivity has been achieved. CPSA on renewable carbon composite paste electrode increases the sensitivity by more than one order of magnitude as compared to voltammetry. It allows the study of CdMT in the mu M concentration range, i.e., the same as is used for the study of CdMT behavior on HMDE. After deposition of CdMT on composite paste electrode at the potential of the complex reduction, three oxidation peaks can be observ ed, one of uncomplexed Cd2+ and two of different S-Cd(II) complexes in the region between -250 mV and + 150 mV. Simultaneous presence of apometallothi onein or of free SH or S-S groups in MT molecule does not interfere in that potential region.