Differential pulse polarographic determination of lead in complex materials after adsorption of its N-methylethylxanthocarbamate complex on microcrystalline naphthalene or on N-methylethylxanthocarbamate-benzyldimethyltetradecylammonium-naphthalene adsorbent

Lead is quantitatively adsorbed as the lead N-methylethylxanthocarbamate (MEXC)-benzyldimethyltetradecylammonium (BDTA) ion pair complex on microcrystalline naphthalene in the pH range 4.0-11.0. The metal is desorbed with HCI and determined by differential pulse polarography. Alternatively lead can be quantitatively adsorbed on the adsorbent (MEXC-BDTA-naphthalene) packed in a column at a flow rate of 1-2 mL/min and determined similarly. Dissolved oxygen is removed by adding a few milliliters of 4% NaBH4 solution. The detection limit is 0.12 microg/mL at the minimum instrumental settings (signal-to-noise ratio, 2). Linearity was obtained over the concentration range 0.3-20.0 microg/mL with a correlation factor of 0.9998 and a relative standard deviation of +/- 0.98%. Various parameters, such as the effect of pH, volume of aqueous phase, flow rate, and the interference of a large number of metal ions and anions, were studied in detail to optimize the conditions for the trace determination of lead in various standard alloys, standard biological materials, and environmental samples.