• Spectroscopy and Spectral Analysis
  • Vol. 42, Issue 7, 2169 (2022)

Abstract

High purity tungsten is an indispensable material in military defense, nuclear industry, semiconductors and other fields for its high melting point, high density and corrosion resistance. Its physical and chemical properties are greatly affected by the content of impurity elements. With the rapid development of new material research, the manufacturing of some key components puts forward higher requirements on the purity of tungsten, and this demand corresponds to strict detection of types and contents of trace impurity elements in high purity tungsten. Inductively coupled plasma mass spectrometry (ICP-MS) is an inorganic mass spectrometry technique with a low detection limit and rapid determination of multiple elements. However, some elements encounter serious mass spectrometry interference problems. Nb and Re in high purity tungsten determined by ICP-MS are interfered with by the doubly charged ions and hydride ions respectively, which are difficult to be eliminated by reaction cells and other techniques. In this paper, the tungsten matrix was separated from the solution by precipitation method using lead acetate as a precipitator to eliminate mass spectral interference. The interference intensity of tungsten matrix on Nb and Re, and the correction effect of standard internal elements on residual matrix and signal drift were mainly investigated. The experimental conditions, including sample dissolution solvents, the dosage of precipitator, acidity, temperature and aging time, were also discussed. The results showed that tungsten matrix solution with a concentration of 1 mg·mL-1 had a significant positive interference effect on the determination of Nb and Re, and interference intensity enhanced with the increase of tungsten mass concentration. When tungsten concentration in solution was less than 2 μg·mL-1 the mass spectral interferences produced by tungsten could be ignored (considering the requirement for a determination limit of 0. 10 μg·g-1). Through various condition tests, the final conditions were as follows: sample was dissolved by mixed acid of nitric acid and hydrochloric acid, 600 μL ammonia (1+1) and 1.0 mL acetic acid-ammonium acetate buffer solution were added, 2.7 mL lead acetate solution with a concentration of 10 g·L-1 was dripped at 250 ℃, and then the solution was heated for 5 min, and entire separation process was about 10 min; Cs was chosen as the standard internal element. The detection limit of Nb and Re was 0.007 and 0.036 μg·g-1, the relative standard deviation was 12% and 4.8%, and the spiked recovery rate was 108% and 105%, respectively. This method is simple and fast, and the precision and accuracy of results meet actual requirements for the analysis of high purity tungsten.