Studies of aluminium complexation to humic and fulvic acids using a method for the determination of quickly reacting aluminium

Abstract

We have recently presented a method for the determination of quickly reacting aluminium in natural waters based on kinetic discrimination in a flow system. This method has been further validated using both an isolated fulvic acid and natural humus-rich waters. Different reaction times were used, further clarifying the response of aluminium complexed 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 and fulvic acids. We have compared results from a series of solutions with varying concentrations of fulvic acids with calculations based on two different models obtained from complexation studies performed by potentiometric titrations and by equilibrium dialysis. The results show fair agreement and suggest that our method can be used for such studies. This approach is more sensitive and rapid than potentiometric titrations, enabling studies of humus interactions with aluminium at concentrations similar to those found in natural waters.