Solid sampling electrothermal atomic absorption spectrometry for analysis of high-purity tungsten trioxide and high-purity tungsten blue oxide

A solid sampling ETAAS method for the direct determination of Ca, Co, Cr, C u, Fe, K, Mg, Mn, Na, Ni and Zn in high-purity tungsten trioxide and tungst en blue oxide powders using a modern spectrometer with transversely heated graphite tube and a solid sampling system is described. The extremely high background caused by the vaporizing tungsten oxides could be eliminated by the reduction to tungsten metal using hydrogen as purge gas during pyrolysi s. Quantification of all elements was performed using calibration curves me asured with aqueous standard solutions. The analyte contents determined wer e between 0.033 (Cu) and 12.6 (Fe) mu g/g for tungsten trioxide and between 0.001 (Co) and 0.5 (Na) mu g/g for tungsten blue oxide. The accuracy was c hecked by comparing the results with those obtained by ETAAS in analysis of HF/HNO3 sample digests and by other methods. Extremely low limits of detec tion being between 0.07 (Mg, Na, Zn) - 2 (Ni) and 0.01 (Mg, Na, Ni) - 1.7 ( Fe) ng/g for tungsten trioxide and tungsten blue oxide, respectively, could be achieved due to almost complete freedom of blank and unusually high app licable sample amounts (5-15 mg for tungsten trioxide and 5-70 mg for tungs ten blue oxide). (C) 1999 Elsevier Science B.V. All rights reserved.