Combined use of differential pulse adsorptive and anodic stripping techniques for the determination of antimony(III) and antimony(V) in zinc electrolyte

Abstract

A knowledge of the concentration of both antimony(III) and antimony(V) is required in zinc plant electrolyte. In this paper, it is shown that an interference-free method to determine the low concentration of antimony in both oxidation states in zinc matrices is achieved by the combined use of differential pulse anodic stripping voltammetry (DPASV) after addition of concentrated hydrochloric acid (total antimony) and differential pulse adsorptive stripping voltammetry (DPAdSV) after addition of dilute hydrochloric and chloranilic acid (antimony(III)). The antimony(V) concentration is therefore calculable from the difference in the DPASV and DPAdSV determinations. In principle, antimony(III) could be determined by DPASV and antimony(V) by DPAdSV. However, in zinc electrolyte, the antimony(III) DPASV method suffers from a small level of interference when antimony(V) is present, while the DPAdSV method for the determination of antimony(V) is significantly interefered with by the presence of antimony(III). Consequently, only the combined use of both the DPASV and DPAdSV gives the required selectivity to achieve a completely interference-free determination of antimony in each oxidation state in zinc plant electrolyte.