Simultaneous preconcentration of Cu, Cd and Pb from soil samples by solid phase extraction and their determination by flame AAS

Simultaneous preconcentration of Cu, Cd and Pb in the form of mixed xanthate-1, 10 - phenanthroline complexes onto microcrystalline naphthalene has been described. The pH range required for quantitative sorption is 5.0-9.0 for each element. Solid mixture containing ternary complexes of metal ions and naphthalene was dissolved in 5 mL of DMF. Cu, Cd and Pb contents were measured using FAAS. The obtained calibration plots were rectilinear over the concentration ranges: 0.03-20.0, 0.01-5.0 and 2.5-100.0 μg L - 1 for Cu, Cd and Pb, respectively. Standard deviations of six replicate determinations of 5.0, 1.0 and 10 μg of Cu, Cd and Pb in 1.0 L of the sample solutions equalled to 1.5, 1.6 and 2.1% respectively. The detection limits found were 0.03, 0.01 and 2.5 μg L - 1 for Cu, Cd and Pb, respectively, which is 200 times lower than for the direct FAAS method. The influence of NaCl, NaNO 3 , Na 2 SO 4 and Na 3 PO 4 on sorption of 5.0, 1.0 and 10.0 μg L - 1 of Cu, Cd and Pb, respectively has been studied. Ca(II) and Mg(II) were found to be not interfering up to the concentration of 25 mmol L - 1 . Enrichment factors obtained for the developed preconcentration procedure involving the solid phase extraction were approximately 200 for the each investigated element. The procedure has been successfully used for the determination of Cu, Cd. and Pb in soil fractions collected from the neighbourhood of industrial and agricultural areas in India.