Determination of trace aluminum in natural waters by flow-injection analysis with fluorescent detection of the lumogallion complex

A flow-injection analysis method is described for the determination of trace levels of aluminum using fluorescent detection of the Al-lumogallion complex. The method is very simple, requiring neither iron masking agents nor micelle forming compounds to improve sensitivity. The detection limit is 3.7 nM with linearity to 37 μM and a relative standard deviation at 1.1 μM of 0.8%. Naturally occurring substances which might be expected to react with aluminum or lumogallion, including citric acid, fulvic acid and iron(III), show no interference. The detection of all forms of aluminum except polymers is demonstrated, making the method useful as a speciation procedure for the determination of free and complexed forms of aluminum in acid impacted as well as non-impacted aquatic systems. Results of analyses of water samples from lakes having a variety of pH values are presented with comparison to results obtained by GFAAS.