Iodide-assisted total lead measurement and determination of different lead fractions in drinking water samples

Abstract

Lead and its compounds are toxic and can harm human health, especially the intelligence development in children. Accurate measurement of total lead present in drinking water is crucial in determining the extent of lead contamination and human exposure due to drinking water consumption. The USEPA method for total lead measurement (no. 200.8) is often used to analyze lead levels in drinking water. However, in the presence of high concentration of the tetravalent lead corrosion product PbO₂, the USEPA method was not able to fully recover particulate lead due to incomplete dissolution of PbO₂ particles during strong acid digestion. In this study, a new procedure that integrates membrane separation, iodometric PbO₂ measurement, strong acid digestion and ICP-MS measurement was proposed and evaluated for accurate total lead measurement and quantification of different lead fractions including soluble Pb²⁺, particulate Pb(II) carbonate and PbO₂ in drinking water samples. The proposed procedure was evaluated using drinking water reconstituted with spiked Pb²⁺, spiked particulate Pb(II) carbonate and in situ formed or spiked PbO₂. Recovery tests showed that the proposed procedure and the USEPA method can achieve 93–112% and 86–103% recoveries respectively for samples containing low PbO₂ concentrations (0.018–0.076 mg Pb per L). For samples containing higher concentrations of PbO₂ (0.089–1.316 mg Pb per L), the USEPA method failed to meet the recovery requirement for total lead (85–115%) while the proposed method can achieve satisfactory recoveries (91–111%) and differentiate the soluble Pb²⁺, particulate Pb(II) carbonate and PbO₂.