CATHODIC ADSORPTIVE STRIPPING VOLTAMMETRY OF INDIUM COMPLEXED WITH MORIN AT A STATIC MERCURY DROP ELECTRODE

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-p entahydroxyflavone (morin) at a static 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, 2 00 mV/s; linear scan mode; filter, 0.1 s; supporting electrolyte, acet ic acid-acetate (0.1 M, pH 3.5); concentration of morin, 1x10(-5) M. T he response of the system was found to be linear in a range of In conc entrations 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 unde r the same conditions. The effect of various potential interferences ( including a variety of cations, anions and organic surfactants) were a lso studied. At less than equimolar concentrations no significant inte rferences were observed. Al3+, Ti4+, Sc3+ and uranyl were found to int erfere at concentrations larger than that of In, but may be masked by fluoride. The observed interference by V5+ may be masked by cyanide. T he method was applied to a sample of jarosite (an industrial residue f rom the refinement of zinc ore) which is known to contain significant quantities of indium.