DETERMINATION OF HEAVY-METALS IN TIO2 WITH ISOTOPE-DILUTION MASS-SPECTROMETRY

An isotope dilution mass spectrometric (IDMS) method has been develope d for the determination of trace impurities (Fe, Cu, Cr, Ni, Cd, Pb, T l, and U) in TiO2; this is of special interest for the quality control of this pigment substance. The measurement of the isotope ratios was carried out using a compact thermal ionization quadrupole mass spectro meter by producing positive thermal ions. For the dissolution of the s ample, microwave digestion with HF was applied. Different separation t echniques (ion exchange chromatography, extraction, electrolytic depos ition) were used for the trace/matrix separation and the element speci fic isolation of the different trace elements to be determined. The de tection limits obtained were (in ng/g): Fe = 90, Cu = 11, Ni = 8, Cd = 7, Pb = 26, Tl = 0.6, U = 0.2. Because IDMS usually results in accura te analytical results, this method can best be used for calibration of other analytical methods, or for the certification of corresponding s tandard reference materials.