Speciation of trace amounts of aluminium in environmental samples by cation-exchange FPLC – ETAAS

Cation-exchange fast protein liquid chromatography – electrothermal atomic absorption spectrometry (FPLC – ETAAS) was applied for the speciation of trace amounts of aluminium. An aqueous 8 mol dm–3 NH4NO3 linear gradient elution in 10 minutes enabled separation of positively charged monomeric aluminium species in aqueous solution. Separated aluminium species were collected in 0.5 cm3 fractions and aluminium determined “off line” after fourfold dilution by ETAAS. The ability of NH4NO3 to completely decompose at low temperature in the graphite tube during the ashing step enabled quantitative and reproducible determination of aluminium. After applying Chelex-100 resin in a cleaning procedure of the eluent, the eluent blank was very low (< 1.0 ng cm–3 Al). When 1 cm3 of sample was injected on the column resin, the limit of detection (3 s) for the separated aluminium species determined by ETAAS was found to be 3 ng cm–3. Good repeatability of measurement of separated aluminium species (relative standard deviation ±5%) was obtained under the recommended analytical conditions. The influence of some inorganic and organic complexing ligands at pH values of 4.0 and 6.0 on the speciation of aluminium was also investigated. The method developed was successfully applied for the speciation of aluminium in soil extracts and natural water samples at ng cm–3 levels.