Determination of lead in soil samples by in-valve solid-phase extraction–flow injection flame atomic absorption spectrometry

Abstract

Solid-phase extraction (SPE) using an immobilized crown ether as an extractant was applied to the flow injection FAAS determination of Pb^II with in-valve minicolumn preconcentration and separation. Lead(II) was first loaded on to a column filled with the crown ether resin from a nitric acid solution (0.8–2.0 mol dm^–3). Among the eluents studied (oxalic acid, ammonium oxalate, citric acid, sodium citrate and tartaric acid), 0.05 mol dm^–3 ammonium oxalate was found to be most suitable. Calibration was made either by variation of the preconcentration time (using a single standard) or by using standard solutions of different concentrations. The detection limit (3σ) was found to be 0.08 µg of Pb and an RSD of 4.1% was achieved for 0.8 µg of Pb^II(n= 15). An upper limit for the working range of 5 µg of Pb^II per sample was found. Interferences of cationic and anionic sample components were found to be negligible. Application to the determination of Pb^II in digested soil samples is described and the method was validated by using certified reference materials.