Trace Level Determination of Lead(II) in Water by Colorimetric-Solid Phase Extraction

Preliminary results on the development of quick, simple analytical method for the low level of lead(II) in water samples are described. The method concentrates lead(II) on a small solid-phase extraction disk, which is then quantified directly on the disk by diffuse reflectance spectroscopy (DRS). This method, termed colorimetric solid-phase extraction (C-SPE), requires only 1–2 min for complete workup and is suitable for use in a wide range of applications, including the microgravity environment on the International Space Station. The procedure first adds an excess of potassium iodide to a 10.0 mL sample at a pH of 3.0–3.5 to produce the anionic PbI₄²⁻ colored complex, which is exhaustively extracted by the disk that was previously impregnated with cetylpyridinium chloride (CPC). The amount of complex extracted is then determined at 420 nm by a hand-held DRS instrument. A linear calibration plot was obtained for lead(II) concentrations from 0.02–2.50 ppm, with a detection limit of 0.010 ppm. Results from interference tests using Ni(II), Cd(II), Zn(II), Cu(II), and Hg(II) yielded deviations of ±10%.