Determination of lead in soil samples by in-valve solid-phase extraction–flow injection flame atomic absorption spectrometry
Solid-phase extraction (SPE) using an immobilized crown ether as an extractant was applied to the flow injection FAAS determination of PbII 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 PbII(n= 15). An upper limit for the working range of 5 µg of PbII per sample was found. Interferences of cationic and anionic sample components were found to be negligible. Application to the determination of PbII in digested soil samples is described and the method was validated by using certified reference materials.