DETERMINATION OF TRACE-ELEMENTS IN BIOLOGICAL STANDARD REFERENCE MATERIALS BY GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY WITH SOLID AND SLURRY SAMPLING

Compared to conventional dissolution methods, solid and slurry samplin g methods offer advantages which include speed, improved sensitivity, a reduced risk of contamination, and a reduced risk of analyte loss. M ost successful graphite furnace atomic absorption spectrometry (GFAAS) results have been obtained by the use of modern furnace technology, w hich includes Zeeman background correction, platform atomization, and matrix modifiers. In this work, solid and slurry sampling were investi gated for the determination of Ag, Cu, Fe, Mn, Pb, and Zn in biologica l National Institute of Standards and Technology (NIST) standard refer ence materials (SRMs) with the use of vintage (1980) GFAAS instrumenta tion, aqueous calibration, and deuterium arc background correction. Al though reasonable accuracy was obtained with solid sampling, the relat ive standard deviation was between 13 and 53 %, which was probably cau sed by the inability of the furnace to reproducibly vaporize the sampl e and the inability of deuterium arc background correction to account for the high background signals. Good accuracy and precision (3 - 13 % ) were obtained with slurry sampling, with the exception of the determ ination of copper in citrus leaves. This low result (three times below the certified value) and high precision (RSD = 31 %) were probably ca used by irreproducible atomization of the sample matrix.