ALUMINUM SPECIATION IN AQUEOUS-SOLUTIONS

An analytical scheme for the speciation of monomeric and polymeric forms of Al in aqueous solutions is presented. After monomer isolation by complexation with pyrocathecol violet (PV) the sample is passed through a column filled with strong cationic exchange resin for polymer retention. Monomeric Al is then determined by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) after preconcentration on silica gel supported 8-hydroxyquinoline (SG-8H) and elution with a 1M HCl/0.1M HNO3 solution. Total Al is determined by ICP-AES on another sample aliquot treated with SG-8H. Polymeric Al is determined by difference between total and monomeric Al. The method was applied to Al speciation in geothermal fluids: a detection limit of 10 ng/mL was obtained with a 5-fold preconcentration factor. Results showed that 100% of total Al in brine and about 80% in hot spring water was in the monomeric form.