INDUCTIVELY-COUPLED PLASMA ATOMIC EMISSION SPECTROSCOPIC DETERMINATION OF TRACE IMPURITIES IN ZRO2-POWDER

Four independent procedures including one using slurry nebulization ICP-AES were developed for the trace analysis of ZrO2 powders. They were evaluated with respect to detection limits, blank values, interferences, accuracy and precision. For the procedures I-III ZrO2 powder was decomposed by fusion with a 10-fold excess of NH4HSO4 and subsequent dissolution of the melt in either water or, after evaporation of NH4HSO4, in diluted HNO3. In procedure I the solution was directly analyzed by ICP-AES, which was optimized with the aid of a simplex algorithm. In procedure II Zr was separated by extraction from 6 mol/l HNO3 with a 0.5 mol/l solution of 2-thenoyltrifluoroacetone (TTA) in xylene. More than 99.5% of the Zr was removed and more than 95% of the trace elements retained. In procedure III the matrix was separated by its precipitation as ZrOCl2.8 H2O from a (1:4) HCl-acetone medium. More than 98% of Zr were removed and more than 90% of the trace elements were retained. In procedure IV the ZrO2 powder was dispersed by ultrasonic treatment in water acidified with HCl (pH 2) and the slurry was directly analyzed by ICP-AES using a Babington nebulizer. The optimization and the analytical features of this procedure will be described in a subsequent paper. In all procedures the calibration was performed by standard addition and matrix matching was not necessary. The detection limits varied from 0.3-mu-g/g (Ca) to 10-mu-g/g (Al). The standard deviations obtained were 1-10% depending on the element and its concentration in the sample. The results of the procedures for 6 commercially available fine ZrO2 powders were found to agree for Al, Ca, Fe, Mg, Na, Ti and Y. A good agreement between the results of the procedures using matrix separation was also observed for Cu, Mn, V, but the concentrations of these elements found by methods without matrix separation were considerably higher. Except for Ca and Mg the blank values encountered were below the detection limits.