Facile spectrophotometric determination of aluminum(III) and copper(II) simultaneously with Alizarin yellow R in aluminum-copper alloys

A facile, highly sensitive, and selective spectrophotometric method has been developed for the determination of aluminum and copper in different alloys. The method is based on the formation of the binary complexes of aluminum and copper with Alizarin yellow R (AYR) [5-(4-nitrophenylazo) salicylic acid] at pH 2.0 and 6.2, respectively, at wavelengths 422 and 445nm with molar absorbtivity 1.1 × 10⁴ l mol^-1 cm^-1 for each one. Aluminum and copper were thus determined in the ranges 0.4-2.0 μg ml^-1 and 1.9-3.6 μg ml^-1, respectively, in the presence of one to another. The detection limits were found to be 1.4 ng ml^-1 of aluminum and 0.015 μg ml^-1 for copper. The relative standard deviations were in all instances less than 1.3%. The proposed method was successfully applied for the simultaneous determination of aluminum and copper in certified reference aluminum-copper alloys.