Column-mode separation and pre-concentration of some heavy metal ions by solvent-impregnated resins containing quinizarin before the determination by flame atomic absorption spectrometry

A simultaneous separation and pre-concentration of Cd(II), Cu(II), Ni(II) and Zn(II) ions from natural water samples for subsequent flame atomic absorption spectrometric determination was proposed. The procedure is based on sorption of the metal ions at the buffering pH of 9.5, on a short column filled with Amberlite XAD-16 impregnated with the complexing agent of 1,4-dihydroxyanthraquinone (quinizarin). The determinations, without the interference of the co-existing substances, were carried out after metals elution with 5 mL of 0.5 mol L-1 HCl. A pre-concentration factor of nearly 100 was obtained using aliquots of 500 mL of the sample solution. For the optimisation of the procedure, effects of sample and eluent flow rate, eluent concentration and its volume were investigated. Beer's law was obeyed in the range of 5.0 10-9 to 1.0 10-7 mol L-1 for Cd(II) and Zn(II), 5.0 10-8 to 1.0 10-6 mol L-1 for Cu(II) and Ni(II) ions. The relative standard deviations of the determinations were 1.87%. The limit of detections for Cd(II), Cu(II), Ni(II) and Zn(II) were found to be 1.3 10-9, 7.1 10-9, 1.3 10-8 and 1.8 10-9mol L-1, respectively. The practical applicability of the method was confirmed using a synthetic certificated reference material and spiked natural water samples.