APPLICATION OF MICROWAVE DIGESTION AND ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY BY REATOMIZATION FROM A 2ND TRAPPING SURFACE TO THE DETERMINATION OF CADMIUM IN PLANT AND ANIMAL-TISSUES

Electrothermal atomic absorption spectrometry by reatomization is based on the use of a small tantalum carbidized graphite vault, ie an arch-shaped surface, inserted inside the tube of a Massmann-type furnace which allows to trap the atomic vapour of the analyte produced by a first atomization of the sample from the tube wall. This technique associated to a microwave nitric digestion was evaluated and compared to more conventional procedures for the determination of cadmium in animal and plant tissues. Results show that the reliability of such an atomizer configuration makes it possible to accurately determine the whole of the chemical forms of Cd present in incompletely mineralized sample solutions without adding matrix modifiers. The absolute detection limit, corresponding to 0.002 mu g g(-1) of Cd for 2 g sample, is very close to the characteristic mass value of 0.43 pg. The accuracy of the proposed method was confirmed by the analysis of standard reference materials. Simple microwave digestion of samples in nitric acid leads to quantitative recovery of Cd as well as a more drastic wet digestion. The vault reatomization proves to be less affected by spectral and chemical interferences than platform atomization, so standardless analysis might be considered.