DIFFERENTIAL-PULSE POLAROGRAPHIC-DETERMINATION OF LEAD USING A RAPID COPRECIPITATION TECHNIQUE WITH INDIUM HYDROXIDE

An analytical method involving lead in water was studied using differential pulse polarography (DPP) after being concentrated by the rapid coprecipitation technique with indium hydroxide. Indium hydroxide coprecipitates quantitatively 1-1500 mug of lead from up to 1000 cm3 of sample solution at a pH of about 9. The presence of indium does not affect the polarogram of lead. Since the concentration of indium is also measurable by DPP, the rapid coprecipitation technique, which does not require a complete collection of the collector precipitate, becomes possible using a known amount of indium and measuring the concentrations of both lead and indium in the final sample solution by DPP. The calibration curve is linear over the 0.04 - 60 mug cm-3 range of lead. Of the 39 diverse ions tested, tin(IV) and selenium(IV) interfered with the determination. The effect of tin(IV), however, could be eliminated by the addition of phosphoric acid. The proposed method is rapid and applicable to the determination of lead in water samples.