ANALYSIS OF SILICON-NITRIDE POWDERS FOR AL, CR, CU, PA, K, MG, MN, NA, AND ZN BY SLURRY-SAMPLING ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A slurry-sampling electrothermal atomic absorption spectrometry method for the determination of Al, Cr, Cu, Fe, K, Mg, Mn, Na, and Zn in powdered silicon nitride is described. The atomization behavior of Ct, Cu, Fe and Mn in aqueous slurries could be improved by using a mixture of(NH4)H2PO4 and Mg(NO3)(2) as chemical modifier. Radiotracer experiments using in situ labeling of the matrix with Si-31 showed that silicon was retained up to similar to 80% after the atomization stage at 2200 degrees C but it could be removed almost quantitatively in the clean-out stage at 2500 degrees C. The modifier facilitated this removal. For all elements, excluding Cu and Mn, quantification by a calibration curve using aqueous standards was possible. As a result of reduction of the blank by use of this technique, the limits of detection of contamination-risk elements such as K, Mg, Na, and Zn could be improved by factors between 8 and 100 over the solution technique, reaching for these elements 4, 7, 12, and 1 ng g(-1) respectively. Upon comparison of the results with those obtained by solution electrothermal atomic absorption spectrometry and neutron activation analysis, good accuracy with the developed slurry sampling technique was shown.