Flame atomic absorption spectrometric determination of trace amounts of Pb(II) and Cr(III) in biological, food and environmental samples after preconcentration by modified nano-alumina

A new solid-phase extraction sorbent was used for the preconcentration of Pb(II) and Cr(III) ions prior to their determination by flame atomic absorption spectrometry. It was prepared by immobilization of 2,4-dinitrophenylhydrazine on nano-alumina coated with sodium dodecyl sulfate. The sorbent was characterized by scanning electron microscopy, N-2 adsorption and Fourier transform infrared spectrometry, and used for preconcentration and separation of Pb(II) and Cr(III) from aqueous solutions. The ions on the sorbent were eluted with a mixture of nitric acid and methanol. The effects of sample pH, flow rates of samples and eluent, type of eluent, breakthrough volume and potentially interfering ions were studied. Linearity is maintained between 1.2 and 350 mu g L-1 of Pb(II), and between 2.4 and 520 mu g L-1 of Cr(III) for an 800-mL sample. The detection limit (3 s, N = 10) for Pb(II) and Cr(III) ions is 0.43 and 0.55 mu g L-1, respectively, and the maximum preconcentration factor is 267. The method was successfully applied to the evaluation of these trace and toxic metals in various water, food, industrial effluent and urine samples.