Cathodic adsorptive stripping voltammetry of indium complexed with morin at a static mercury drop electrode

Abstract

A new method is described for the determination of indium based on the cathodic adsorptive stripping of In(III) complexed with 2′,3,4′-5,7-pentahydroxyflavone (morin) at a satic mercury drop electrode. Optimal conditions were found to be: accumulation potential, −0.30 V (vs. Ag/AgCl); final potential, −1.00 V; accumulation time, 60 s; scan rate, 200 mV/s; linear scan mode; filter, 0.1 s; supporting electolyte, acetic acid-acetate (0.1 M, pH 3.5); concentration of morin, 1 × 10 −5 M. The response of the system was found to be linear in a range of In concentrations from 0 ppb to 40 ppb. The detection limit was found to be 0.4 nM (0.05 ppb) with 5 min of accumulation time. This is compared to a detection limit of 6.9 nM (0.8 ppb) for simple anodic stripping under the same conditions. The effect of various potential interferences (including a variety of cations, anions and organic surfactants) were also studied. At less than equimolar concentrations no significant interferences were observed. Al 3+ , Ti 4+, Sc 3+ and uranyl were found to interfere at concentrations larger than that of In, but may be masked by fluoride. The observed interference by V 5+ may be masked by cyanide. The method was applied to a sample of jarosite (an industrial residue from the refinement ofzinc ore) which is known to contain significant quantities of indium.