DETERMINATION OF TRACE ALUMINUM BY DIFFERENTIAL PULSE ADSORPTIVE STRIPPING VOLTAMMETRY OF ALUMINUM(III)-8-HYDROXYQUINOLINE COMPLEX

A rapid and sensitive differential-pulse adsorptive stripping voltammetric method, based on the formation of an electroactive complex between aluminium(III) and 8-hydroxyquinoline (HOx), is presented for the determination of trace levels of aluminium. The complex showed an oxidative peak potential at + 0.876 V vs. Ag/AgCl (saturated KCl) at a glassy carbon (GC) electrode in aqueous ammonium acetate (0.024 M, pH 6.8). A good linear relationship between the peak current and Al(III) concentration in the ranges 4.00 x 10(-8)-5.00 x 10(-6) and 8.00 X 10(-6)-4.00 x 10(-5) M were observed. In the lower Al(III) concentration region, the anodic peak was the result of the stripping of the adsorbed Al(III)-HOx complex, whereas in the higher concentration range, the diffusional oxidation current of the solution species predominated. A surface saturation region was observed from 5.00 x 10(-6) to 8.00 x 10(-6) M Al(III). Relatively few interferences were found and these were easily masked. The detection limit for Al(III) for this method is 1.00 x 10(-8) M and ten determinations of Al(III) at 1.00 x 10(-7) M gave a relative standard deviation of 6.2%. The method was employed in the analysis of Al(III) in a US Environmental Protection Agency water pollution quality control sample (WP 386) and excellent agreement with the certified value was obtained.