Differential-pulse polarographic determination of cadmium in various environmental samples after adsorption of its quinolin-8-olate complex on to microcrystalline naphthalene

Abstract

A highly selective, rapid and economical differential-pulse polarographic method has been developed for the determination of trace amounts of cadmium in various standard alloys and environmental samples after adsorption of its quinolin-8-olate on to microcrystalline naphthalene. The cadmium complex is quantitatively adsorbed on to microcrystalline naphthalene in the pH range 6.1–10.0 and is determined by differential-pulse polarography after desorption in 10 ml of 1 mol l^–1 hydrochloric acid. Dissolved oxygen is removed by adding a few millilitres 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 relative standard deviation of ±0.74%. Characterization of the electroactive process included an examination of the degree of reversibility. Various parameters, such as the effect of pH, volume of aqueous phase and interference of a number of metal ions on the determination of cadmium, have been studied in detail to optimize the conditions for its determination in complex materials.