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 sampling methods offer advantages which include speed, improved sensitivity, a reduced risk of contamination, and a reduced risk of analyte loss. Most successful graphite furnace atomic absorption spectrometry (GFAAS) results have been obtained by the use of modern furnace technology, which includes Zeeman background correction, platform atomization, and matrix modifiers. In this work, solid and slurry sampling were investigated for the determination of Ag, Cu, Fe, Mn, Pb, and Zn in biological National Institute of Standards and Technology (NIST) standard reference materials (SRMs) with the use of vintage (1980) GFAAS instrumentation, aqueous calibration, and deuterium arc background correction. Although reasonable accuracy was obtained with solid sampling, the relative standard deviation was between 13 and 53 %, which was probably caused by the inability of the furnace to reproducibly vaporize the sample 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 determination of copper in citrus leaves. This low result (three times below the certified value) and high precision (RSD = 31 %) were probably caused by irreproducible atomization of the sample matrix.