Simultaneous Calibrationless Determination of Zinc, Cadmium, Lead, and Copper by Flow-Through Stripping Chronopotentiometry

Zn, Cd, Pb and Cu are deposited in a porous flow-through electrode plated with mercury and then are stripped by constant current while the stripping time is measured. Since complete electrochemical deposition can be achieved, the analyte concentrations can be directly obtained from Faraday's laws i.e., the method is denoted as calibrationless. The influence of the deposition potential, stripping current, carrier electrolyte composition, Cu content and sample matrix was investigated. The optimum conditions are: deposition potential: –1600 mV, stripping current: 200 μA, carrier electrolyte: 0.1 mol/L sodium sulfate at pH 4–5. The dynamic range of the method is from about 0.1 ng/mL to few mg/mL. The repeatability of the method is 1–2 % in the optimum concentration range. The procedure was applied to the analyses of water samples, geological, and biological materials.