Highly sensitive determination of vanadium (V) by catalytic adsorptive stripping voltammetry. Substituent effect on sensitivity III

Abstract

Catalytic adsorptive stripping voltammetry has been a powerful technique for trace metal determination. We now report one of the most sensitive voltammetric methods developed for vanadium. The determination is based on the complexation of vanadium with quercetin-5-sulfonic acid (QSA), adsorption of V(V)-QSA and reduction to V(III)-QSA onto HMDE; and finally in the scan step electrochemical reduction of V(III)-QSA to V(II) at about −0.78V applying differential pulse catalytic adsorptive stripping voltammetry. With the aim of comparing the effect of the sulfonic group on the sensitivity of the determination, two methods were developed using quercetin (Q) and Quercetin-5-sulfonic acid (QSA) as complexing and adsorbing ligands. The effects of various operational parameters such as pH, ligand, and potassium bromate concentration (CQ, CQSA, CKBrO3), potential, and adsorption time (Eads, tads) were optimized. The best results were obtained with QSA, and the optimal experimental parameters were pH: 7.0; CQSA: 0.6×10−6molL−1, CKBrO3: 3.5×10−2molL−1, Eads: 0.0V, and tads: 30s. Under the best experimental conditions the RSD for a V(V) solution (0.1μgL−1) was 3.4% for ten successive assays. Linearity was maintained up to 0.35μgL−1 and the detection limit was 0.23ngL−1 (tads: 30s; CQSA: 0.6×10−6molL−1). The method was validated using certified reference water (TMDA – 61.2) and finally, the method was applied to the determination of vanadium in tap water, purified drinking water, river water, and commercial water for chromatography.