SPECIATION OF ALUMINUM IN SOIL EXTRACTS BY EMPLOYING CATION-EXCHANGE FAST PROTEIN LIQUID-CHROMATOGRAPHY INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY

A fast protein liquid chromatographic-inductively coupled plasma (ICP) atomic emission spectrometric procedure was developed for the speciat ion of Al over a wide pH range, from acidic to alkaline regions, Posit ively charged monomeric Al species in synthetic aqueous solutions were separated from polymeric, neutral and negatively charged species on a cation-exchange fast protein LC column, Linear gradient elution with aqueous NaNO3 (8 mol dm(-3)) at a flow rate of 1.0 cm(3) min(-1) over 10 min was employed for the separation, The separated Al species were determined 'off-line' by ICP atomic emission spectrometry in 0.5 cm(3) fractions, which were diluted prior to analysis; yttrium was added as the internal standard, Retention times were found to be 1.5 min for A l(OH)(2)(H2O)(4)(+) [Al(OH)(2)(+)], 4.0 min for Al(OH)(H2O)(5)(2+) [Al (OH)(2+)] and 4.5 min for Al(H2O)(6)(3+) [Al3+], Good reproducibility of measurement (relative standard deviation 1.5%) was obtained in the optimum concentration range, The limit of detection (3s) for the separ ated Al species was found to be 120 ng cm(-3) (1.0 cm(3) sample), The distribution of Al species over a wide pH range agreed with the report ed calculated data and, in general, agreed also with the data from the 8-hydroxyquinoline spectrophotometric method, An investigation of the effect of inorganic and organic complexing ligands on the speciation of Al indicated that positively charged [Al(SO)(4)(+), AlF2+] and nega tively charged (oxalate and citrate) Al species co-eluted with Al(OH)( 2)(+) and were separated from Al(OH)(2+) and Al3+ species, while AlF2 co-eluted with Al(OH)(2+) species. At lower pH values (e.g., 4.0), al uminium citrate was partially co-eluted with Al3+ and Al(OH)(2+) speci es. The same observations were found when soil extracts were analysed.