Simple detection of trace Pb²⁺ by enrichment on cerium phosphate membrane filter coupled with color signaling

A Pb²⁺ selective membrane filter was fabricated from the fibrous CeO(H₂PO₄)₂·2H₂O (CeP) crystals by blending with cellulose fiber. Enrichment of ppb level of Pb ²⁺ was achieved simply by filtration of aqueous sample solution through the membrane filter. Pb²⁺ was strongly retained on the membrane filter by accommodation into the interlayer gallery of a CeP crystal. Visual detection of the enriched Pb²⁺ was achieved by subsequent color signaling as PbS deposit upon treatment of the membrane filter with 3% Na₂S solution. The analytical procedure and sample treatment conditions were optimized with respect to pH of the sample solution, filtration rate and masking of interfering ions. Detection of 20 ppb of Pb²⁺ was not interfered by the presence of 1000-fold of Ca²⁺, Mg ²⁺, and up to 100-fold of Fe³⁺ and Cu²⁺ by masking with 1 × 10^-3 mol dm^-3 of iminodiacetic acid (IDA). Most anions including phosphate (20 000 times) did not interfere with the determination of Pb²⁺. The present simple method was applied to the determination of Pb²⁺ in real samples like mine valley water.