Determination of La(III) by adsorptive stripping voltammetry using carminic acid in acetate buffer

La(III) was determined by differential pulse voltammetry, based on the adso rptive accumulation of the La(LII)-carminic acid complex on a I hanging mer cury drop electrode in 0.1 mol L-1 acetate buffer, at pH = 5.8. Cyclic volt ammetry and electrocapillary curves were used to characterize the redox and adsorptive behavior. The optimum conditions were found to be: carminic aci d concentration of 3.2x10-7 mol L-1, an accumulation potential of -0.70 V v s ESC, and an accumulation time of 2 min. A linear increase was observed wi th a La(III) concentration up to 1.4x10-8 mol L-1 with a 0.998 correlation coefficient, and a detection III mit of 1.7x10-9 mol L-1. At a La(III) conc entration of 7.2x10-9 mol L-1,a relative standard deviation of 4.8 % was ob tained.