STUDIES OF ALUMINUM COMPLEXATION TO HUMIC AND FULVIC-ACIDS USING A METHOD FOR THE DETERMINATION OF QUICKLY REACTING ALUMINUM

We have recently presented a method far the determination of quickly r eacting aluminium in natural waters based on kinetic discrimination in a flow system. This method has been further validated using both an i solated fulvic acid and natural humus-rich waters. Different reaction times were used, further clarifying the response of aluminium complexe d with humic and fulvic acids. Equilibrium dialysis was also used as a reference method for comparison. With the reaction time used normally , 2.3 s, aluminium complexed with humic or fulvic acids was shown not to be measured with our method. These results suggest that our method may be used for studies of the complexation of aluminium with humic an d fulvic acids. We have compared results from a series of solutions wi th varying concentrations of fulvic acids with calculations based on t wo different models obtained from complexation studies performed by po tentiometric titrations and by equilibrium dialysis. The results show fair agreement and suggest that our method can be used for such studie s. This approach is more sensitive and rapid than potentiometric titra tions, enabling studies of humus interactions with aluminium at concen trations similar to those found in natural waters.