SLURRY-ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRIC DETERMINATION OF ALUMINUM AND CHROMIUM IN VEGETABLES USING HYDROGEN-PEROXIDE AS A MATRIX MODIFIER

Fast heating programmes for determining aluminium and chromium in vegetables using electrothermal atomic absorption spectrometry with slurry sampling are developed using wall atomization. The build-up of carbonaceous residues inside the atomizer is avoided by adding 4% hydrogen peroxide and 1% nitric acid to the slurries instead of using an air-ashing stage. In accordance with fast-programme methodology, the conventional drying and charring steps are replaced by a modified drying stage, simplifying the heating programmes. For suspensions containing 0.1% m/V of ground vegetables, the relative standard deviation (RSD) is about +/-5% for aluminium. For chromium determination, the use of 0.5-1% m/V suspensions leads to RSDs close to +/-4%. Calibration is carried out using aqueous standards. The aluminium and chromium contents of a number of vegetable samples obtained by using the slurry approach agree with those obtained by means of a conventional procedure based on the total dissolution of the samples. The reliability of the procedures is also confirmed by analysing two certified reference materials.