CARBON-PASTE ELECTRODE AND MEDIUM-EXCHANGE PROCEDURE IN ADSORPTIVE CATHODIC STRIPPING VOLTAMMETRY OF SELENIUM(IV)

An adsorptive cathodic stripping voltammetric method for the determination of Se(IV) is described. The method is based on the detection of the piazselenol complex formed by Se(IV) with 2,3-diamino naphthalene (2,3 DAN) at pH 2 (0.01 mol L(-1) HCl + 0.1 mol L(-1) KCl). The method is based on a medium-exchange scheme and a carbon paste electrode (CPE). The preconcentration step is carried out at open circuit, and then the complex is stripped our: by linear sweep voltammetry (LSV) after medium exchange (0.1 mol L(-1) HNO3 + 0.1 mol L(-1) KNO3 where the working electrode is transferred). The method is characterized by a precision better than 8% and a limit of quantitation (10 times the standard deviation of the blank) of 1.25 x 10(-7) mol L(-1) (for 20 minutes of preconcentration time). The use of CPE coupled with the medium-exchange scheme reduces the interferences (especially by different classes of surfactants) and improves the selectivity (much better than in the usual cathodic stripping voltammetry on mercury).