DIRECT DETERMINATION OF CADMIUM AND LEAD IN GEOLOGICAL AND PLANT MATERIALS BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A laboratory-assembled atomic absorption spectrometer and graphite cup atomizer were evaluated for direct analysis of solid samples. A number of geological (soil and sediment) and botanical reference materials were analysed for lead and cadmium either by direct introduction (0.02-5 mg) or by a slurry technique (5-200 mg). Integrated absorbance was measured, and aqueous standards were used for calibration. An (NH4)2HPO4 chemical modifier was necessary in the analysis of botanical samples. The effect of particle size on the accuracy and precision of analytical results was studied. Atomization of small sample aliquots (20-500-mu-g) by direct 'weighing in' sample introduction technique requires fine grinding (1-mu-m) whereas slurry sample introduction is more tolerant to particle size effects.