Relevance of the reaction of aluminium with pyrocatechol violet to speciation and complexation capacity analysis

Pyrocatechol Violet is shown to separate uncomplexed aluminium effectively in the presence of model and natural ligands. Application to freshwater samples shows that the measurement is critically dependent on reaction time. Use of a short reaction time reflects the nature of the colloidal ligands rather than the presence of inorganic aluminium. A short reaction time with Pyrocatechol Violet and separation by equilibrium dialysis were not found to be suitable separation methods for inorganic and organic aluminium species. The results indicate the analytical difficulties in determining inorganic aluminium in natural water samples. However, it is shown that the reaction of aluminium, after 30 min, with Pyrocatechol Violet is promising for the assessment of aluminium complexation by fulvic acid.