DUAL STAGE PRECONCENTRATION SYSTEM FOR FLAME ATOMIC-ABSORPTION SPECTROMETRY USING FLOW-INJECTION ONLINE ION-EXCHANGE FOLLOWED BY SOLVENT-EXTRACTION

A dual stage preconcentration system based on flow injection on-line i on-exchange and solvent-extraction has been developed for flame atomic absorption spectrometry. Lead is taken as a model trace element. A co lumn packed with Amberlite IRC-718 cation exchanger is incorporated in to the FI manifold. The analyte is retained on the column by time-base d sample loading and eluted by 1 mol/L HNO3. The eluate is subsequentl y merged with potassium iodide and tetrabutylammonium bromide (TBABr), and isobutyl methyl ketone (IBMK), Lead is extracted on-line into IBM K as the ion-pair formed between the iodoplumbate anion and tetrabutyl ammonium cation, The organic phase is separated from the aqueous phase by a gravity phase separator, 50 mu L of concentrate is introduced in to the nebulizer-bumer system of the spectrometer. An enhancement fact or of 550 is achieved with a 30 mt sample consumption at a sampling fr equency of 30/h, The precision (relative standard deviation) is 2.4% a t 10 mu g/L level and the detection limit is 0.3 mu g/L (3 sigma). The method was successfully applied to the determination of lead in water samples.