FLOTATION SEPARATION AND FLAME ATOMIC ABSORPTION SPECTROMETRIC DETERMINATION OF TRACE AMOUNT OF LEAD IN SOME ENVIRONMENTAL SAMPLES

摘要

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 various environmental samples. The flotation process was carried out using a 250-mL aliquot of the aqueous solution at the buffering pH of 8.50 in which the ion-associate complex was floated at the interface of the aqueous/xylene phases. The ion-associate complex was then dissolved in 5 mL of acidic solution of 0.05 M KClO3 and the Pb(II) content was determined by flame atomic absorption spectrometry (FAAS). By this method, a preconcentration factor of 50 can be achieved so that the determination of trace amounts of Pb(II) ions is feasible in the range of 1x10~(-7) to 1.2x10~(-6) M. The LOD and RSD (n=7) were obtained as 1.5x10~(-8) M and 1.5%, respectively. It was found that a large number of cations and anions even at high considerably foreign ion/Pb(II) ratios were not interfered. In treatment with a SRM water sample and a synthetic liquid extract of vegetable, the recoveries were more than 95%s, which confirmed validity of the method. The method was satisfactorily applied for determining of trace amount of Pb(II) in some complex matrices.