SLURRY SAMPLING FOR THE DETERMINATION OF LEAD, CADMIUM AND THALLIUM IN SOILS AND SEDIMENTS BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRYWITH FAST-HEATING PROGRAMS

To determine the lead and cadmium content of soils and sediments, the samples are suspended in water containing 5% (v/v) concentrated hydrof luoric acid before injected into the electrothermal atomizer. For thal lium determination a 30% hydrofluoric acid solution is used as the sus pension medium. In accordance with fast-heating methodology, the conve ntional ashing step is replaced by a modified drying stage performed b y programming the instrument to 400 degrees C. No modifier other than hydrofluoric acid is required. Calibration is performed directly using aqueous standards for cadmium and lead determination. For thallium th e standard additions method is recommended. The results obtained for f ive certified reference materials show the reliability of the procedur es.