DETERMINATION OF ALUMINUM AND ITS FLUORO COMPLEXES IN NATURAL-WATERS BY ION CHROMATOGRAPHY

Ion chromatography was applied to the determination of aluminium and its fluoro complexes in natural waters. The separation was carried out on a cation-exchange column. The aluminium species were detected by postcolumn reaction with Tiron followed by UV spectrophotometry. The method requires the adjustment of the pH and ionic strength of the sample to those of the mobile phase immediately prior to injection. Al3+, AlF2+ and AlF2+: are eluted separately while all hydroxo complexes are readily dissociated and eluted along with Al3+ under these conditions. The sum of peak areas, which represents the total aluminium concentration, was conserved whatever the amount of fluoride in the sample. Linearity of calibration was observed over the range 20-2000 mu g l(-1). Further, the speciation of fluoro-aluminium complexes as determined experimentally by ion chromatography is in good agreement with calculations based on complexation constants. The applications and limitations of the method are discussed.