Determination of trace impurities in high-purity zirconium dioxide by inductively coupled plasma atomic emission spectrometry using microwave-assisted digestion and wavelet transform-based correction procedure

This paper describes a rapid, accurate and precise method for the determination of trace Fe, Hf, Mn, Na, Si and Ti in high-purity zirconium dioxide (ZrO₂) powders by inductively coupled plasma atomic emission spectrometry (ICP-AES). The samples were dissolved by a microwave-assisted digestion system. Four different digestion programs with various reagents were tested. It was found that using a mixture of sulfuric acid (H₂SO₄) and ammonium sulfate ((NH₄)₂SO₄), the total sample dissolution time was 30 min, much shorter than that required for conventional digestion in an opening system. The determination of almost all of the target analytes suffered from spectral interferences, since Zr shows a line-rich atomic emission spectrometry. The wavelet transform (WT), a recently developed mathematical technique was applied to the correction of spectral interference, and more accurate and precise results were obtained, compared with traditional off-peak background correction procedure. Experimental work revealed that a high Zr concentration would result in a significant decrease in peak height of the analyte lines, which was corrected by standard addition method. The performance of the developed method was evaluated by using synthetic samples. The recoveries were in the range of 87-112% and relative standard deviation was within 1.1-3.4%. The detection limits (3σ) for Fe, Hf, Mn, Na, Si and Ti were found to be 1.2, 13.3, 1.0, 4.5, 5.8 and 2.0 μg g⁻¹, respectively. The results showed that with the microwave-assisted digestion and the WT correction, the detection limits have improved by a factor of about 5 for Fe, 4 for Mn and Ti, 3 for Si, and 2 for Hf and Na, respectively, in comparison with conventional open-system digestion and off-peak correction. The proposed technique was applied to the analysis of trace elements above-mentioned in three types of ZrO₂ powders.