Determination of impurities in niobium carbide by high-pressure acid decomposition/ICP-AES

In order to determine impurities (thirteen elements) in niobium carbide (Nb C) by inductively coupled plasma atomic emission spectrometry (ICP-AES), a sample dissolution procedure using acids was examined. A 0.25 g amount of N bC powder sample was taken in a Teflon pressure vessel, and 2 ml of hydrofl uoric acid (1+1) and 10 ml of nitric acid (1+ 9) were added. The vessel was sealed and kept at 160 degreesC for 16 hours in a drying oven. After cooli ng, the mixture was filtrated so as to remove any small amount of insoluble free carbon which existed in the sample. The filtrate was transferred to a 100 ml calibrated flask, and diluted with distilled water to volume. Thirt een elements (Al, Ca, Co, Cr, Fe, Mg, Mn, Ni, Ti, Ta, V, W and Zr) were det ermined by ICP-AES. The matrix effects of Nb on the background levels and t he emission intensities of the elements of interest were compensated by usi ng matrix-matched standard solutions for the calibration. Thirteen elements in commercial NbC powder samples were determined with good precision. The recoveries of thirteen spiked elements were 95% for Ni to 103% for Co, Fe a nd Mn; the detection limits were 0.04 mug g(-1) for Mg to 11 mug g(-1) for Al.