In-situ vaporization and matrix removal for the determination of rare earth impurities in zirconium dioxide by electrothermal vaporization inductively coupled plasma atomic emission spectrometry

A novel method for the determination of trace rare earth impurities in ZrO₂ powder has been developed based on electrothermal vaporization inductively coupled plasma atomic emission spectrometry. A polytetrafluoroethylene slurry was used as a fluorinating reagent to convert both the matrix (Zr) and the analytes (rare earth elements) into fluorides with different volatilities at a high temperature in a graphite furnace. The more volatile ZrF₄ was removed in-situ by selective vaporization prior to the determination of the analytes, removing matrix spectral interferences. Under optimum operating conditions, the absolute detection limits of the analytes varied from 0.04 ng (Yb) to 0.50 ng (Pr) with relative standard deviations less than 5%. The recommended approach has been successfully applied to the determination of trace rare earth impurities (La, Pr, Eu, Gd, Ho and Yb) in ZrO₂ powder and the results were in good agreement with those obtained by pneumatic nebulization inductively coupled plasma atomic emission spectrometry after the separation of the matrix using a solvent extraction procedure.