Alfred J. Baca: Quantification of Metals Released by Metallothionein Adsorbates at Mercury Film Electrodes by Differential Pulse Voltammetry and Electrochemical ICP-Atomic Emission Spectrometry Electrodes and Cells.  A schematic representation of the homemade thin-layer electrochemical cell is shown in Figure 1a. This design is similar to that in References [[30]] and [[32]], except for two minor modifications. First, a 0.5-mm-diameter Ag wire was embedded in the PEEK square block adjacent to a 6-mm-diameter glassy carbon electrode (Bioanalytical Systems, Inc., West Lafayatte, IN). The distance between the working and the Ag electrodes is 1.2 mm (face view of Figure 1a).  Upon polishing the glassy carbon electrode and the Ag disk, a layer of AgCl was formed on top of the Ag disk by carefully leaving a drop of the coating solution (Bioanalytical Systems, CF-2200) onto the Ag disk for 60 s, followed by rinsing the electrode with a copious amount of water. The resultant quasi reference electrode was found to possess a stable potential and was calibrated against a standard Ag/AgCl reference electrode. The second change is that the Pt foil is not affixed onto the stainless steel block. The contact of the Pt foil counter electrode with the stainless steel block was made by aligning and tightening the working electrode, the separation Teflon gasket (MF-1047, Bioanalytical System), and the Pt foil assembly with four stainless steel screws (Figure 1a). Since the Pt foil is not permanently attached onto the stainless steel cell block, cleaning and replacement of it becomes easier. The choice of a specific cell design and the valve configuration is dependent on the consideration of sample consumption, the influence of the cell volume on the elution profile, and the necessity of maintaining a stable cell potential. Since the present work is concerned with protein samples, we opted to use a low-volume cell (ca. 2 ?L) that does not contain a reference electrode compartment. The absence of a separate electrode compartment also helps eliminate any possible sample entrapment in dead space.    Instruments.  The combination of the homemade thin-layer cell with an ICP-atomic emission spectrometer (ICP-AES) is described elsewhere.[30, 32] Briefly, the cell was positioned upstream of the sample introduction system of an axially viewed ICP-AES (Spectro Analytical Instruments, Fitchburg, MA) through a six-port rotary valve and a MicroMist nebulizer (Spectron, Santa Barbara, CA) mounted onto a Scott-type spray chamber. A Microneb 2000 controller (CETAC Technologies), consisting of a gas displacement pump and a module for changing the valve configuration (Figure 1b), was used to control the carrier flow rate and the valve configuration. Throughout this work, a flow rate of 75 ?L/min was chosen. This value is optimal in terms of preserving the mercury film on the glassy carbon electrode and delivering a sufficient amount of sample to the ICP-AES for reasonable signal intensity. Figure 1