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, N a, Ni, Pb, Sr, Tk and Zn in powdered titanium dioxide is described. Th e behaviour of the titanium matrix in the atomizer and its interferenc es with the determination of Al, Fe, Co, Ni and Mn were studied. A tun gsten carbide modified graphite tube was used to improve the signal sh ape and the repeatability for the determination of Fe. For all element s, except for Cd and Pb, quantification by a calibration curve establi shed with aqueous standards was possible. No chemical modifier was use d throughout in order to minimize contamination. For the contamination risk elements such as Ca, Fe, K, Mg, Na and Zn, the slurry sampling t echnique allows to achieve limits of detection (3 sigma of the blank) 5-20 times lower than the solution technique, resulting for these elem ents in values of 1, 3, 0.5, 0.5, 0.9 and 2 ng g(-1), respectively, an d, generally being in the range of 0.2 ng g(-1) (Cd) to 10 ng g(-1) (A l and Tl). The results obtained by the slurry sampling technique are c ompared with those of other independent methods including four solutio n methods and neutron activation analysis. (C) 1997 Elsevier Science B .V.