Polarographic study of Eriochome cyanine R and its aluminium complexes

Abstract

The behaviour of the two main cathodic polarographic waves of the dye Eriochhrome cyanine R (ECR), A at - 0.45V, and B at -1.0 vs. SCE, were followed from acetate buffer pH 4.8 in the presence of Al3+ ions. Two new waves (E and F) were noticed in the potential region between waves A and B. From amperometric titrations, the mole ratios 1:1 and 2:3 of the formed Al-ECR complexes, which correspond to the waves E and F, were determined. The procedure for indirect analytical determination of aluminium was done by monitoring the variation of the wave A height as a function of the Al3+ ion concentration. A linear response of the wave heigh vs. the metal-ion concentration was obtained in the range fron 0.05 to 0.5 mg/l with standard deviation of ±3% determined for the aluminium ion concentration of 0.1 mg/l (n = 10).