Quantification of metals released by metallothionein adsorbates at mercuryfilm electrodes by electrochemical ICP-atomic emission spectrometry

Electrochemistry combined on-line with inductively coupled plasma-atomic em ission spectrometry (EC/ICP-AES) was used to study the electrode reactions of rabbit liver metallothionein (W) adsorbates at thin mercury films (TMFs) . Three major oxidation peaks, with peak potentials at - 1.20, - 0.75 and - 0.32 V, were observed. Through the correlation of the DPV characteristics to the elution of the Zn2+ and Cd2+ ions monitored by time-resolved ICP-AES responses, the peak at - 1.20 V was assigned to the anodic stripping of Zn (Hg). For the first time, both Zn2+ and Cd2+ were found to be associated wi th the initial oxidation at - 0.75 V by EC/ICP-AES. In the subsequent volta mmetric scans, the peak at - 0.75 V decreased but remained steady and did n ot result in the elution of additional metals. The initial decrease in curr ent is suggested to originate from the anodic stripping of the Cd(Hg) amalg am and the Zn-Cd intermetallic compound in the TMF. The anodic peak remaini ng at - 0.75 V was attributed to the formation of the cystine analog from t he electrodimerization of the uncomplexed cysteine, residues in NIT molecul es. The quantities of Cd2+ and Zn2+ under the oxidation peaks were measured by EC/ICP-A-ES. Our work demonstrates that EC/ICP-AES. is a viable techniq ue for elucidating relatively complicated electrode reactions that involve metal release and transfer. (C) 2001 Elsevier Science B.V. All rights reser ved.