Enrichment of metal-APDC complexes on admicelle-coated alumina for water analysis

Aggregates of sodium dodecyl sulfate (SDS) formed on alumina particles were employed as enrichment vehicles of hydrophobic metal-chelates from water samples. To a 50 cm(3) suspension of 1.5 g of purified alumina was added 100 mg of SDS; the mixture was then acidified to pH 2, where the anionic surfactant was strongly adsorbed on positively charged alumina surfaces to form admicelles. Nanogram quantities of heavy metals (Co, Ni, Cu, Cd and Pb) in water were complexed with APDC at pH 2-6 and quantitatively incorporated in the admicelles. A nearly complete desorption was achieved for those metals (except for Co) in 4 mol dm(-3) nitric acid with the aid of ultrasonic irradiation. A multielement determination was performed by ICP-MS. The reliability of the proposed method was evaluated by analyzing a certified reference seawater sample.