Determination of aluminium in water samples by adsorptive cathodic stripping voltammetry in the presence of pyrogallol red and a quaternary ammonium salt

A fast, sensitive and selective method for the determination of aluminium based on the reaction of the metal with pyrogallol red (PR) in the presence of tetrabutylammonium tetrafluoroborate (TBATFB) to form an Al(PR)3x9TBATFB complex which is adsorbed on the mercury electrode is presented. Under these conditions complexation of aluminium is rapid and no waiting period or heating of the sample is required. The reduction current of the accumulated complex is measured by scanning the potential in the cathodic direction. The variation of peak current with pH, adsorption time, adsorption potential, ligand and quaternary ammonium salt concentration, and some instrumental parameters, such as stirring rate in the accumulation stage, and step amplitude, pulse amplitude and step duration while obtaining the square wave voltamperograms were optimized. The best experimental parameters were pH 8.5, (NH4Ac–NH3 buffer), CPR = 25 μmol L−1, CTBATFB over 75 μmol L−1, tads = 60 s, and Eads = −0.60 V versus Ag/AgCl. A linear response is observed over the 0.0–30.0 μg L−1 concentration range, with a detection limit of 1.0 μg L−1. Reproducibility for 9.0 μg L−1 aluminium solution was 2.3% (n = 6). Synthetic sea water and sea water reference material CRM-SW were used for validation measurements. Aluminium in urine samples of a volunteer who ingested 800 mg of Al(OH)3 was analyzed.