Simultaneous Determination of Traces of Lead and Cadmium in Various Samples by Differential Pulse Polarography after Adsorbing Their 1-(2-Pyridyazol)-2-Naphthol onto Microcrystalline Naphthalene

A highly selective, rapid and economical differential pulse polarographic method has been developed for the determination of trace amounts of cadmium and lead present together in various standard alloys and biological samples after adsorption of their 1-(2-pyridylazo)-2-naphthol complexes on microcrystalline naphthalene. Cadmium and lead complexes are equantitatively adsorbed on microcrystalline naphthalene in the pH range of 8.2-11.0 for cadmium and 8.4-11.5 for lead. After filtration, the solid mass is shaken in 10 mL of 1M hydrochloric acid and these metals are determined simultaneously by differential pulse polarography (DPP). Detection limits are: 0.07 mg/mL for Cd and 0.1 mg/mL for Pb (signal to noise ratio=2). While linearity is maintained in the concentration range 0.1-150 mg-mL for Cd and 0.1-300 mg/mL for Pb with a correlation coefficient of 0.9996 and relative standard deviations of 0.98 and 1.1%, respectively. 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 and lead have been studied in detail to optimize the conditions for their simultaneous (based upon the difference in their Ep values) determination in complex materials.