TRACE ENRICHMENT OF ALUMINUM IONS ON IMMOBILIZED DESFERRIOXAMINE

Aluminium was quantitatively preconcentrated in a flow-injection system using a column containing desferrioxamine immobilized on porous glass. The metal ions were eluted with 2 M nitric acid for determination by atomic absorption spectrometry. It was necessary to add a soluble chelate former to prevent precipitation of aluminium hydroxides from the standard solutions. Computer modelling with known equilibrium constants indicated that a buffer with lactate as a ligand was adequate. The pH range was restricted to 5.5-6.0 for quantitative uptake of aluminium ions because of the competition of protons with the binding sites of desferrioxamine in the acidic region and precipitation of hydroxides in the alkaline region. The ligand-exchange kinetics were also of importance and the column was therefore kept at 50-degrees-C. The immobilized desferrioxamine column showed good stability and could be used continuously over a period of at least 2 months. Aluminium from peritoneal dialysis solutions was preconcentrated on immobilized desferrioxamine and determined by graphite furnace atomic absorption spectrometry.