Determination of trace amounts of aluminium in tap water by spectrophotometry after collection on a membrane filter using Chrome Azurol S and Zephiramine

Abstract

A sensitive and selective spectrophotometric method for the determination of aluminium(III) using Chrome Azurol S and Zephiramine is described. The ion-pair precipitate formed between Zephiramine and perchlorate ions is effective for the enrichment of aluminium(III) on a membrane filter as its ternary complex with Chrome Azurol S and Zephiramine. The solid-state absorbance of the complex on the membrane filter is measured at 640 and 700 nm against a blank thin layer and the difference is calculated. Although the calibration graph does not obey Beer's law good reproducibility is observed, the relative standard deviation for 0.10 µg of aluminium(III) in a 20-ml sample volume being 3.1%(n= 5). A ligand buffer solution, composed of trans-cyclohexane-1,2-diaminetetraacetic acid and an excess of zinc(II), is effective for masking interferences from foreign ions, particularly iron(III). The method has been applied to the determination of aluminium in tap water.