Adsorptive stripping voltammetric determination of aluminium using Arsenazo III

A new analytical method for the indirect determination of trace amounts of aluminium(III) is based on the adsorptive accumulation of an azo dye, Arsen azo III, an the hanging mercury drop electrode. In the presence of AI(III) forming complexes with the dye, its peak occurring at -330 mV decreases. Op timized experimental conditions were found as follows: supporting electroly te, acetate or chloroacetate-acetate buffer (pH 3.6); accumulation potentia l, -50 mV vs SCE; accumulation time, 120 s; Arsenate III concentration, 5.1 0(-7) mel l(-1); scan rate, 20 mV s(-1); initial potential, -500 mV; final potential, 0 mV; FSDPV mode; pulse amplitude, 50 mV; pulse duration, 100 ms ; pulse interval, 10 ms. Under these experimental conditions, the calibrati on dependence was linear in the concentration range 0-6 mu mol l(-1) with a detection limit of 3.7 10(-8) mol l(-1) (1 ppb, calculated as 30 for n = 1 0). Interference of iron(III) can be suppressed by addition of L-ascorbic a cid, the effect of numerous divalent metal ions is negligible. Serious inte rfering effects were observed for U(VI) as UO22+, both Cr(III) and Cr(VI), and F-. The method developed was verified using a certified reference mater ial (SRM 1575 Pine Needles); no statistically significant differences betwe en the determined and declared contents were found.