Determination of trace impurities in titanium dioxide by slurry sampling electrothermal atomic absorption spectrometry

A slurry sampling electrothermal atomic absorption spectrometry method for the determination of Al, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sr, Tk and Zn in powdered titanium dioxide is described. The behaviour of the titanium matrix in the atomizer and its interferences with the determination of Al, Fe, Co, Ni and Mn were studied. A tungsten carbide modified graphite tube was used to improve the signal shape and the repeatability for the determination of Fe. For all elements, except for Cd and Pb, quantification by a calibration curve established with aqueous standards was possible. No chemical modifier was used throughout in order to minimize contamination. For the contamination risk elements such as Ca, Fe, K, Mg, Na and Zn, the slurry sampling technique allows to achieve limits of detection (3 sigma of the blank) 5-20 times lower than the solution technique, resulting for these elements in values of 1, 3, 0.5, 0.5, 0.9 and 2 ng g(-1), respectively, and, generally being in the range of 0.2 ng g(-1) (Cd) to 10 ng g(-1) (Al and Tl). The results obtained by the slurry sampling technique are compared with those of other independent methods including four solution methods and neutron activation analysis. (C) 1997 Elsevier Science B.V.