Determination of impurities in titanium oxide by ICP-AES

Abstract

ICP-AES was applied to the determination of impurities, Al, Ca, Fe, K, Mg, Na, Nb, Si and Zr, in titanium oxide samples. Titanium oxide (0.5 g) was decomposed with 2.5 ml of hydrofluoric acid and 2.5 ml of hydrochloric acid at 150 °C for 3 h in a Teflon pressure vessel. For the use of a quartz torch, the resulting solution was diluted to 100 ml with 2% w/v hydrochloric acid, after the addition of 1.6 g of boric acid for masking fluoride ion. In the case of the laboratory-manufactured alumina torch, the solution was diluted to 100 ml with 2%w/v hydrochloric acid. Because of incomplete masking of fluoride ions with boric acid, the quartz torch gave a higher background intensity at Si I 251.61 nm and a higher detection limit of Si. The alumina torch had adequate resistivity to hydrofluoric acid. For each element except Si, both torches gave the similar detection limits. The titanium matrix appreciably reduced the emission intensities of the elements of interest and increased the background level. Therefore, the standard solution for calibration required the matrix-matching with equal amount of titanium to that in the sample solutions. The analytical results by using two torches were in good agreement.