Alfred J. Baca: Quantification of Metals Released by Metallothionein Adsorbates at Mercury Film Electrodes by Differential Pulse Voltammetry and Electrochemical ICP-Atomic Emission Spectrometry Electrochemistry combined on-line with inductively coupled plasma-atomic emission spectrometry (EC/ICP-AES) was used to study the electrode reactions of rabbit liver metallothionein adsorbates at thin mercury films (TMFs) and to quantify the metals released from MT adsorbates under oxidoreductive conditions. The differential pulse voltammetric (DPV) behavior of the MT adsorbates at the TMFs was found to be analogous to that observed at a dropping mercury electrode. Three major oxidation peaks, with peak potentials at –1.20 V, -0.75 V, 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). The electrode processes at –0.75 V are more complex. For the first time, both Zn2+ and Cd2 were found to be associated with the oxidation peak at –0.75 V by EC/ICP-AES. In the subsequent DPV scan, the peak at –0.75 V decreased but remained steady in latter scans and did not result in the elution of additional metals. The initial current decrease was suggested to be the completion of the anodic stripping of the Cd(Hg) amalgam and the Zn-Cd intermetallic compound in the TMF. The anodic peak remained at –0.75 V was attributed to the formation of the cystine analog from the electrodimerization of the uncomplexed cysteine residues in MT molecules. Both Cd2+ released at –0.75 V and Zn2+ under the two oxidation peaks at –1.20 V and –0.75 V were quantified by EC/ICP-AES. The average extent of metal release per MT was calculated by comparing the EC/ICP-AES results to the total metals in the MT solution introduced into the electrochemical flow cell. Our findings suggest that caution should be exercised when conventional voltammetric techniques are used to study the MT binding towards Zn2+, since the stripping of the Cd-Zn intermetallics might be overwhelmed by the Cd(Hg) oxidation and/or the cysteine electrodimerization reactions and consequently is undetectable by voltammetry. Our work demonstrates that EC/ICP-AES is a viable hybrid technique for elucidating relatively complicated electrode reactions that involve metal release and transfer.