Spectrophotometric studies on the simultaneous determination of cadmium and mercury with 4-(2-pyridylazo)-resoreinol

A new method for direct spectrophotometric determination of cadmium with 4-(2-pyridylazo)-resorcinol is reported. Absorption maximum, molar absorptivity and Sandell's sensitivity of the 1:1 (M:L) complex are 510 nm, 2.5 x 10(5) 1 mol(-1) cm-(1) and 3.55 ng cm(-2), respectively. A linear calibration graph, is obtained up to 4.49 mug ml(-1). The zero-crossing measurement technique is found suitable for the direct measurement of the first-derivative value at the specified wavelengths. Cadmium(II) (0.42-9.2 mug ml(-1)) and mercury(II) (0.35-7.4 mug ml(-1)) in different ratios have been determined simultaneously. A critical evaluation of the proposed method is performed by statistical analysis of the experimental data. The developed method was applied to the simultaneous spectrophotometric determination of Cd and Hg in some synthetic mixtures and was found to give satisfactory results. (C) 2002 Elsevier Science B.V. All rights reserved.