Simultaneous determination of aluminium and beryllium at the subnanogram per millilitre level by solid-phase derivative spectrophotometry

The applicability of derivative solid-phase spectrophotometry is demonstrated for the resolution of mixtures of aluminium and beryllium with closely overlapping absorption profiles. A spectrophotometric method for the simultaneous determination of beryllium and aluminium based on first-derivative solid-phase spectrophotometry is proposed. Both metal ions were fixed on a dextran-type anion-exchanger gel at pH 4.4, as coloured complexes with Eriochrome Cyanine R in the presence of ethylenediaminetetra-acetic acid. The absorption spectrum of the gel, packed in a 1 mm cell, was recorded directly. The application range is up to 60 ng ml(-1) for aluminium and up to 4.0 ng ml(-1) for beryllium, and the RSD is 3.5% and 3.8%, respectively. The detection limit is 0.04 ng ml(-1) for beryllium and 2.25 ng ml(-1) for aluminium. The relative error obtained in the analysis of a synthetic aqueous solution is 1.50% for beryllium and 1.75% for aluminium. The method was applied to the determination of both analytes in natural water, orange juice, geological and botanical samples.