Wall-jet flow cell for stripping potentiometry

Abstract

Samples were peristaltically injected, through a 0.32 mm diameter nozzle, on to the surface of a combined working, reference and counter electrode, which was held upside-down, and then allowed to drain down the electrode to waste. Sample analyte ions were enriched potentiostatically, by means of reduction and simultaneous amalgamation, on the mercury film coated 3 mm diameter glassy carbon working electrode. As the flow was stopped a droplet, of approximate volume 20 µl, of either the sample or a suitable stripping medium, remained on the electrode, maintaining electrical contact between the three electrodes and, at the same time, creating quiescent conditions, and thus reproducible hydrodynamic conditions, at the sample–electrode interface. Stripping was then performed in the constant-current stripping potentiometry mode. Repetitive analysis of a sample containing 5 µg l^–1 of lead(II) yielded a relative standard deviation of 1.5%.