The electrochemical reduction of selenium ( + 4 ) on hanging mercury drop electrode (HMDE) has been studied using square wave voltammetry (SWV). The product of the first, very complex electrode reaction can be further reduced in a process characterized by reactant and product adsorption. The height of the stripping peak increases up to four times with the addition of Cu2+ ions, although the electrode reaction becomes less reversible. The square wave cathodic stripping peak currents are an order of magnitude higher than the corresponding differential pulse values, but the detection limit (3 x mol/L) is practically the same for both techniques. The concentration of selenium ( + 4 ) in rainwater samples has been determined.

Abstract. Current minimum, which sometimes appears as a part of the net response in differential pulse polarography (DPP), was studied in systems characterized by a pronounced IR drop or reactant adsorption. Experimental results obtained on a static mercury drop electrode (SMDE) clearly indicate that this effect is highly influenced not only by solution resistance (or intentionally added resistors) and reactant concentration, but also by both timing parameters (drop time, pulse duration) and electrode surface area. Presentation of the net response along with its components, demonstrates that the current minimum originates from the maximum on dc component, minimum on pulse component or both. In practice, DPP minimum, obtained in measurements with a SMDE, can be treated as an additional diagnostic parameter for the recognition of reactant adsorption or poor experimental conditions (i.e. high resistance within electrode system or low conductivity of the electrolyte medium). (doi: 10.5562/cca2054)

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