ANALYSIS OF SILICON-CARBIDE POWDERS WITH ICP-MS SUBSEQUENT TO SAMPLE DISSOLUTION WITHOUT AND WITH MATRIX REMOVAL

ICP-MS has been employed for the analysis of silicon carbide powders i n connection with high pressure acid decomposition without and with ma trix removal by evaporation. The powder is decomposed by treatment of a 250 mg sample with a mixture of HNO3, H2SO4 and HE Prior to the anal yses with ICP-MS the solutions have to be diluted to a matrix concentr ation of 500 mu g/ml related to SiC in order to realize full long-term precision. The results obtained for Li, B, Na, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, Ga, Sr, Y, Zr, Nb, Ag, Cd, In, Sn, Sb, Pa , La, Ce, Pr, Nd, I-If, Ta, W, Tl, Pb, Pi, Th and U in SiC powder S-93 3 are shown to be in good agreement with those of independent methods, such as INAA, ICP-AES with slurry atomization and ICP-AES subsequent to sample decomposition. For extending the use of ICP-MS to elements s uch as Mg, Ca, Sc and Ti at the relevant concentrations in SiC powders , a more effective matrix removal by evaporation of the decomposition solution to near dryness has been successfully applied. Its advantages have been proven by the results of high resolution ICP-MS. It has bee n found by analyses of the treated sample solutions for the residual S i and C with ICP-MS that over 99% of the matrix and also of the acids used for decomposition are removed. For B, Al and Fe losses were found to occur at concentration levels of some mu g/g, 200 mu g/g and 300 m u g/g, respectively, and all other elements were detected with very go od recoveries. For all 36 elements investigated in this work the detec tion limits could be improved from the ng/g to the pg/g range by remov al of the matrix. The analytical range could be improved, in particula r for In, Tl, Bi and U.