Measurement of L subshell X-ray fluorescence crosssections at 59.54 keV and L subshell fluorescence yields for elements in the atomic range 55 <=Z<=81

In the present paper, an on-line system for enrichment and determination of lead is proposed. It is based on the chemical sorption of lead(II) ions on a minicolumn packed with polyurethane foam loaded with 2-(2-benzothiazolylazo)-2-p-cresol (BTAC) reagent. After preconcentration, lead(II) ions are eluted by 0.10moll-1 hydrochloric acid solution and determined directly by flame atomic absorption spectrometry (FAAS). Chemical and flow variables as well as effect of other ions were studied. The results demonstrated that lead could be determinate with an enrichment factor of 26 for a sample volume of 7.0ml and preconcentration time of 1min. The detection limit (3s) was 1.0µgl-1 and the precision (assessed as the relative standard deviation) reached values of 6.0-0.7% in lead solutions of 10-500µgl-1 concentration, respectively. The enrichment factor and the detection limit can be further improved by increasing preconcentration time without degradation in the efficiency due to the favorable kinetics and low hydrodynamic impedance of the present system. Achieved sampling frequency was 48samples per hour. The effect of another ions in concentrations agreeing with biological samples was studied. It was found that the proposed procedure has necessary selectivity for lead determination in seafood and other biological samples. The accuracy was confirmed by analysis of the followings certified reference materials: fish tissue IAEA, lobster hepatopancreas NRCC TORT-1 and citrus leaves NIST 1572. Recoveries of spike additions (0.2 or 1.0µgg-1) to several seafood samples were quantitative (90-107%). These results proved also that the procedure is not affected by matrix interferences and can be applied satisfactorily for lead determination in samples of shrimp, oyster, crab, fish and mussel contaminated by it.