Graphite furnace analysis

The impact of microwave digestion, hot injection of solutions and chemical modification on the analysis of biological samples by electro-thermal atomic absorption spectrometry (AAS) has been assessed. The stabilizing effects of palladium and ruthenium modifiers were compared. Although ruthenium has a higher atom appearance temperature, palladium was a more useful modifier when samples other than water were analysed. When 2 μg of palladium (as PdCl2) was preconditioned in hydrogen at 500 degC, volatile elements were retained at char temperatures up to 1000-1100 degC. This allowed similar atomizer programmes to be used for Cd, Cu, Fe, Mn and Pb and accurate determination of the analytes in solutions of reference materials was achieved against aqueous standards Rapid drying of the solutions by hot injection at 120 degC reduced programme time to just over 1 min. A combination of microwave digestion ,hot injection of 40% (w/v) HNO3 solutions and Pd modification produced a rapid and sensitive method for determination of Cd and Pb at sub-μg g-1 levels in vegetable and protein foodstuffs. Palladium modification also proved useful in simultaneous multielement determination by continuum source AAS. The picogram detection limits obtained for Cr, Mn and Pb were similar to line source AAS values recorded with the same compromise programme. Accurate determination of Cd, Cr, Cu, Mn, Mo and Pb in NIST SRM 1566 Oyster Tissue indicated the potential of continuum source AAS for multielement determinations. The advantages of palladium modifications were also illustrated for furnace atomic non-thermal excitation spectrometry (FANES) with hollow-cathode discharge. Maximum char temperatures of Ag, Ga, Hg, Pb, Sb and Se were increased by 300-600degC in the presence of 1 μg of Pd, although detection limits were a factor of 2 poorer. (author). 58 refs.; 2 figs.; 17 tabs