Determination of aluminum in highly saline samples by electrothermal AAS after matrix removal

A FIAS (Flow-Injection Atomic Spectrometry) analytical procedure has been developed for aluminum preconcentration and determination at the ng/L level in highly saline samples, based on solid-phase extraction. Analyte enrichment and matrix removal are simultaneously achieved by on-line complexation of Al3+ with 4,5-dihydroxy-1,3-benzenedisulphonic acid (Tiron) and retention of the Al-Tiron complex on a macroporous anion-exchange resin. Selective release of Al3+ is obtained by elution with 0.1 mol/L HCl; the eluate can be collected in a small volume and analyzed by Graphite Furnace AAS, or carried on-line to a Flame AAS. The method resulted in a detection limit of 1 ng/L for GF-AAS determination, with a linear range comprised between 1 ng/L and 50 mu g/L. Precision is better than 5% on a 10 mu g/L Al3+ solution. The whole procedure has been successfully applied to Al determination in dialysis concentrates.