AQUEOUS AL(III) SPECIATION BY HIGH-PERFORMANCE CATION-EXCHANGE CHROMATOGRAPHY WITH FLUORESCENCE DETECTION OF THE ALUMINUM-LUMOGALLION COMPLEX

Soluble complexes of aluminum, including fluorides, citrates, acetates , and silicate, were separated from uncomplexed Al and quantitated usi ng gradient elution cation exchange HPLC. Fluorescence detection of th e Allumogallion complex allowed detection as low as 7 nM with linearit y to 58 mu M and relative standard deviations of 3% at the 2 mu M leve l. Dissociation of the complexes on the column and inadequate detectio n of Al organic complexes, problems in previous methods, were not obse rved. Species concentrations at various pH and ionic strengths agreed well with equilibrium speciation calculations for solutions of aluminu m citrates and aluminum fluorides. The formation constants were determ ined for AlOSiO3H32+, an aluminum species considered in the modeling o f acid-impacted aquatic systems, and for AlCit-(-H)(-), a species pred ominant in basic solutions. Formation constants were also estimated fo r two aluminum acetate complexes, AlOAc2+ and AlOHOAc+, the identifica tion of the latter being previously unconfirmed.