Extraction-Spectrophotometric Determination of Cadmium with N-Hydroxy-N,N’-diphenylbenzamidine and 4-(2-Pyridylazo)resorcinol

Abstract

A simple, sensitive and selective spectrophotometry method for the determination of cadmium at trace levels in various environmental samples is reported. The binary complex formed between cadmium(II) and N-hydroxy-N, N’-diphenylbenzamidine (HDPBA) is extracted with chloroform at pH 9.0±0.2 and shows a maximum absorbance at 400 nm with a molar absorptivity of 1.96×10⁴ 1 mol^-1 cm^-1. The sensitivity of the binary complex was enhanced by adding 4-(2-pyridylazo)resorcinol (PAR) after extracting cadmium(II) with HDPBA at pH 9.0±0.2. The reddish-orange complex shows a maximum absorbance at 520 nm with a molar absorptivity of 5.9×10⁴ 1 mol^-1 cm^-1. This method follows Beer’s law up to 1.6 μg cm^-3 Cd. Various experimental parameters such as the effect of solvents, pH, time, temperature, concentration of the reagent and order of addition of reagents have been studied for establishing the optimum conditions for the determination of cadmium. The effect of diverse ions was examined; the results indicated that most of the common ions like Fe(III), Co(II), Ni(II), Cu(II), Mn(II), Al(III), V(V), Cr(III), Mg(II), Mo(VI), Sn(IV) and Bi(III) do not interfere. The detection limit of cadmium in this method is 0.05 μg cm^-3. The relative standard deviation of the method for ten replicate measurements is ±1.4%. This method has been successfully employed for the determination of cadmium in various environmental samples.