Amperometric determination of Se(IV) with on line preconcentration by flowinjection anlysis.

The experimental conditions for the indirect amperometric detection of Se(I V) by flow injection analysis have been optimized. The method is based on t he Se(IV) reduction to Se(0) in acid medium in presence of an excess of iod ide, being generated yotrion species which is electroactive and amperometri cally detected at vitreous carbon electrode. The signal depends on the quan tity of Se(IV) in the samples. Under optimized conditions, analytical condi tions of the method were determined. The detection and quantification limit s were 4.8 mu g l(-1) and 15.9 mu g l(-1), respectively. Because of the met hod proposed for its application to the determination of Se(IV) in natural water samples, it became necessary to increase the detection sensitivity an d an on-line concentration stage was coupled. This stage is carried out on an anionic resin exchange (Dowex 1-X8). The detection and the quantificatio n limits were in this case 0.06 mu g l(-1) and 0.2 mu g l(-1), respectively . The online preconcentration stage increases the sensibility of the ampero metric detection which allows the Se(IV) determination at mu g l(-1) levels .