BATCH AND FLOW DETERMINATION OF URANIUM(VI) BY ADSORPTIVE STRIPPING VOLTAMMETRY ON MERCURY-FILM ELECTRODES

Uranium(VI) was determined by square wave adsorptive stripping voltammetry on a rotating-disc mercury-film electrode using 8-hydroxyquinoline as a complexing agent (batch mode), or, alternatively, on a wall jet mercury-him electrode with cupferron as complexing agent (flow-through mode). For the how-through configuration, the combination of a novel wall jet cell with an automated flow system and a commercial computer-controlled potentiostat allowed complete keyboard control of the sequence of operations. Both continuous flow and flow injection (FI) schemes for preconcentration were assessed, and various instrumental parameters are discussed. Linearity held typically for a concentration range of two orders of magnitude (for 60 s preconcentration), It was found that, whereas the batch and continuous-flow modes are more suitable for the determination of lower concentrations of U-VI (<10(-7) mol l(-1)), FI is ideal for higher concentrations (>10(-7) mol l(-1)). The batch and flow methods were, finally, applied to the determination of U-VI in a reference sea-water sample with accuracies of 7.2 and 4.2%, respectively, and relative standard deviations of 7.8 and 8.3%, respectively.