ADSORPTIVE STRIPPING VOLTAMMETRIC MEASUREMENTS OF TRACE NIOBIUM LEVELS FOLLOWING CHELATION WITH CUPFERRON

Trace levels of niobium can be determined by adsorptive stripping voltammetry, with controlled interfacial accumulation of the niobium/cupferron complex onto the hanging mercury drop electrode. Optimal conditions (5 x 10(-6) M cupferron in acetate buffer (pH 4.0), a preconcentration potential of -0.2 V, and differential pulse stripping) allow convenient quantitation of mug/L (ppb) concentrations. The detection limit is 83 ppt (10 minute preconcentration); the response is linear over the 0-20 ppb range: and the relative standard deviation (at the 5 ppb level) is 2.0%. Most cations do not interfere in the determination of niobium. Complexation with cupferron also allows analogous trace measurements of vanadium.