Abstract：Graphite material is an ideal inorganic non-metallic material with high chemical stability, good conductivity, and good wear resistance. As graphite is a refractory substance, it is difficult to test the trace element contents by using common chemical methods or conventional instrumental analyses. Common problems in the graphite analysis by the Fire-ICP method are as follows: (1) the individual elements are easily lost during the high temperature burning pretreatment process, and (2) the graphite cannot be dissolved completely during the process of adding acid dissolution. Therefore, many scholars began using solid analytical technology to determine the impurity contents in graphite. Glow discharge mass spectrometry (GDMS) is a technology combining glow discharge power supply (GD) with mass spectrometry (MS). It has advantages of simple pretreatment, weak matrix effect, low detection limit and high sensitivity. It has become a division of high pure metal and semiconductor materials at home and abroad. Relative sensitivity factor (RSF) is a coefficient used to correct GDMS analysis results. For GDMS analysis, most elements still have obvious matrix effect in different matrixes. In order to make GDMS analysis as a quantitative analysis method, it is necessary to use the standard material matching the matrix to correct the RSF. However, most of the GDMS analysis is based on the standard relative sensitivity factor (RSFStd) provided by instrument manufacturers and only semi quantitative analysis results can be obtained. This paper describes an analytical method to determine the content of 9 elements in graphite materials using GDMS. Through the optimization of the discharge conditions, the suitable discharge conditions of graphite were determined (current intensity as 55 mA, discharge gas flow rate as 450 mL·min-1). Under optimized analytical conditions, 9 impurities (Mg, Cr, Ni, Ti, Fe, Cu, Al, Si and Ca) were determined. The result of t-test showed that there was significant difference between the results of most elements and the reference value. In order to obtain more accurate results, the corresponding RSFx of each element was required to establish quantitative analysis methods. Through experiments, the effects of different current intensity and discharge gas flow on the RSF value of 9 elements were investigated, and the causes of the influencing factors were discussed. The experimental results showed that the current intensity and discharge gas flow have a great influence on the RSF value of most elements. The discharge gas flow has the greatest influence on the RSF value, and the RSF value of each element varies between 15% and 405%. Under selected conditions, the content of 9 impurity elements, such as Mg, Cr and Ni in graphite materials, was quantitatively analyzed by RSFx value. The t-test sig value of the test results was more than 0.05, indicating that there was no significant difference between the measured results and the reference value, and the accuracy of the method was significantly improved. The relative standard deviations (RSD) were between 3.2% and 9.9%. The method can meet the need for the analysis of high purity graphite materials above 4N purity.
王梓任，王长华，胡芳菲，李继东. 辉光放电质谱法直接分析石墨中痕量杂质[J]. 光谱学与光谱分析, 2019, 39(04): 1256-1261.
WANG Zi-ren, WANG Chang-hua, HU Fang-fei, LI Ji-dong. Quantification of Trace Impurities in Graphite by Glow Discharge Mass Spectrometry. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(04): 1256-1261.
