DIFFERENTIAL-PULSE POLAROGRAPHIC-DETERMINATION OF CADMIUM IN VARIOUS ENVIRONMENTAL-SAMPLES AFTER ADSORPTION OF ITS QUINOLIN-8-OLATE COMPLEXONTO MICROCRYSTALLINE NAPHTHALENE

A highly selective, sensitive, rapid and economical differential-pulse polarographic method has been developed for the determination of trac e amounts of cadmium in various standard alloys and environmental samp les after adsorption of its quinolin-8-olate on to microcrystalline na phthalene. The cadmium complex is quantitatively adsorbed on to microc rystalline naphthalene in the pH range 6.1-10.0 and is determined by d ifferential-pulse polarography after desorption in 10 ml of 1 mol l(-1 ) hydrochloric acid. Dissolved oxygen is removed by adding a few milli litres of 4% NaBH4 solution. The detection limit is 0.7 ppm (signal-to -noise ratio = 2) and the linearity is maintained in the concentration range 0.7-17 ppm, with a correlation coefficient of 0.9997 and a rela tive standard deviation of +/-0.74%. Characterization of the electroac tive process included an examination of the degree of reversibility. v arious parameters, such as the effect of pH, volume of aqueous phase a nd interference of a number of metal ions on the determination of cadm ium, have been studied in detail to optimize the conditions for its de termination in complex materials.