EVALUATION OF FLOW-INJECTION IN LEAD HYDRIDE GENERATION ATOMIC-ABSORPTION SPECTROMETRY

The present study explores the attractiveness of combining flow-inject ion (FI) with lead hydride generation atomic absorption spectrometry ( AAS) to improve the selectivity and sensitivity of analysis. Lead hydr ide was generated in three acid-oxidant media: HNO3-(NH4)(2)S2O8, lact ic acid-K2Cr2O7 and HNO3-H2O2. The effect of chemical parameters (acid -oxidant concentration and NaBH4 concentration) was investigated and t he performance of each generation medium in terms of interferences, se nsitivity and detection limits was compared with that obtained in batc h mode. In all cases improved sensitivity (HNO3-H2O2, 0.8 ng Pb; lacti c acid-K2Cr2O7, 0.2 ng Pb; (NH4)(2)S2O8-HNO3, 4 ng Pb) was obtained, m ost notably in HNO3-H2O2, which provided 12 times higher sensitivity t han in batch mode and sharper absorption peaks. Furthermore, interfere nce by Cu and Ni was lower in the proposed FI-HG system. Compared with the batch mode, about 10 to 100 times higher concentrations of interf erent are tolerated in the sample. The use of FI also allows work at a lower NaBH4 concentration. The method was applied to the determinatio n of lead in water samples with a sampling frequency of 180 samples pe r hour. In terms of both sensitivity and freedom from interferences, l actic acid-K2Cr2O7 was the best of the generation media tested.