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

In order to determine impurities (eleven elements) in vanadium carbide (VC) by inductively coupled plasma atomic emission spectrometry (ICP-AES), a sample dissolution procedure using acids was examined. After a 0.25 g amount of vanadium carbide powder sample was taken in a Teflon pressure vessel, 2 mi of nitric acid (1+1) and 2 mi of hydrofluoric acid (1+1) were added. The vessel was then sealed and kept at 160 degrees C in a drying oven. The time taken to decompose depended on the sample (16 or 40 h). The mixture was filtered so as to remove the small amount of free carbon which existed in the sample, itself, and could not be decomposed by these acids. The filtrate was transferred to a 100 mi calibrated flask with 20 mi of 4% boric acid, and diluted with distilled water. Eleven elements (Al, Ca, Co, Cr, Fe, Mn, Mo, Ni, Si, Ti and W) were determined by ICP-AES. The matrix effects on the background levels and the emission intensities of the elements were compensated by using matrix-matched standard solutions for calibration. Eleven elements in commercial VC powder samples were determined with good the precision. For most elements, the values obtained by the proposed method were found to be in good agreement with both those obtained by high-pressure acid decomposition with atomic absorption spectrometry and those obtained by the fusion-acid method using potassium nitrate with ICP-AES. The detection limits were 0.18 mu g g(-1) for Mn to 6.5 mu g g(-1) for W.