Flotation separation and electrothermal atomic absorption spectrometric determination of lead in water samples

A flotation method based on formation of an ion-associate complex between ferroin and Pb(II)-thiosulfate complex is proposed for the quantitative separation and preconcentration of Pb(II) content in water and some vegetable samples. The flotation process was carried out using a 250-mL aliquot of the aqueous solution at a buffering pH of 8.50. After separating the ion-associate complex, it was dissolved in 5 mL of heated 1 M HNO3, and the Pb(II) content was determined by electrothermal atomic absorption spectrometry. The determination of Pb(II) was carried out in the range of 1.6 x 10(-9) to 1.2 x 10(-8) M. The limit of detection and relative standard deviation were obtained as 8.5 x 10(-10) M and 1.73%, respectively. It was found that a large number of cations and anions, even at high much foreign ion/Pb(II) ratios, were not interfered. The validity of the method was confirmed by determining the Pb(II) contents in two Standard Reference Materials and a synthetic liquid extract of vegetable sample. It was then applied satisfactorily for determination of Pb(II) in several plant foodstuffs, drinking-water, and tap-water samples.