Prior to the CV experiment, each group is required to clean their working electrodes. A three-electrode system is set up with a C-3 cell filled with 10 mL of the digested sample solution, a gold working electrode, a Ag/AgCl reference electrode, and a platinum wire as the auxiliary electrode (Figure ). Triplicate CV runs of the analyte were obtained followed by incremental addition of the standard to the sample (Figure ). Students are encouraged to clean the surface of the working electrode in between runs to avoid fouling the electrode. Both cathodic and anodic peak currents should respond linearly with increasing analyte concentration. Any deviation observed may be corrected by additional electrode polishing. All CVs were collected at a s scan rate of 200 mV/s over a potential range of -300 mV to 800 mV.