In order to determine impurities in tantalum carbide and tantalum nitride by ICP-AES, sample dissolution procedures by acids were examined. A powder sample of 0.25 g tantalum nitride was taken in a Teflon pressure vessel, and 2 ml of hydrofluoric acid (1 + 1) and 1 ml of 31% hydrogen peroxide solution were added. After sealing, the vessel was kept at 160 degrees C for 16 h in a drying oven. Though it has been reported that tantalum nitride is insoluble in acids, these tantalum nitride powder samples dissolved completely. After cooling, the solution was transferred to a 100 ml calibrated flask with 20 ml of 4% boric acid and 5 ml of nitric acid, and diluted with distilled water. A powder sample of 0.25 g tantalum carbide was also taken in a Teflon pressure vessel, and 5 ml of nitric acid, 3 ml of 31% hydrogen peroxide solution and 1 ml of hydrofluoric acid were added. The vessel was kept at 180 degrees C for 20 h after predecomposition at room temperature for 2 h. This solution was also transferred to a 100 ml calibrated flask with 20 ml of 4% boric acid. Among the matrix components, the tantalum matrix increased the background level for all the elements without, however, influencing the emission intensities. The increase in the background level was corrected by subtracting the background intensity near each analytical line in ICP-BES measurement. Therefore, the common standard solutions of nitric acid, hydrofluoric acid and boric acid could be used for the determination of impurities in tantalum carbide and tantalum nitride. The proposed method was applied to some commercial samples, The analytical results were in good agreement with those obtained by AAS, and the reproducibility was satisfactory.
