ALUMINUM SPECIATION IN SOME SYNTHETIC SYSTEMS - COMPARISON OF THE FAST-OXINE, PH 5.0 EXTRACTION AND DIALYSIS METHODS

A procedure for the fractionation of aqueous aluminum was evaluated on synthetic systems using 8-hydroxyquinoline (oxine) at pH 5.0 or 8.3 and reaction times of 15 s or 60 min. For comparison of the speciation of the most reactive forms of Al, dialysis tubing with a molecular weight cutoff of 1000 was used. In the hydroxide and fluoride systems the fast-oxine, pH 5.0 method clearly distinguishes between different forms of Al. In systems containing citrate and oxalate, low molecular weight organic complexing agents, the fast-oxine method produced a clearer distinction between inorganic and organically complexed Al than did the dialysis method. In contrast, the AL species in systems containing fulvic acid and leaf litter leachate were much more clearly differentiated by the dialysis method. The fast-oxine, pH 5.0 reaction appears to extract a fraction of the organically complexed Al; this supports the hypothesis that natural organic complexes have a wide range of bond strengths to metal ions.