Relative Sensitivity Factor of Nitrogen in Steel by Helium/Glow Discharge-Mass Spectrometry

We have already reported that, in argon glow discharge-mass spectrometry, relative sensitivity factors (RSF) for nitrogen are different among various steel samples. In this paper, the RSF was measured in detail when helium was employed as the plasma gas, and further RSFs for other elements such as carbon were also checked. 30 disk-shaped standard reference samples used in this experiment comprised four different groups depending on their chemical compositions, including stainless steel of Japanese Iron and Steel Certified Reference Materials (JSS CRMs). The sample surfaces were prepared up to a mirror-polishing with alumina (1 μm). The preliminary discharge time was set to be 120 min, as considering the results of preliminary experiments. The average RSF-value obtained for different alloy groups were 0.990-1.314 in the helium ion source, whereas the values were 11.03-28.69 in the argon ion source, indicating that their variations were much smaller in the case of helium. Variations of RSF-value for other elements were expressed as the RSDs of less than 6%. When using the helium ion source, the analytical result of nitrogen for actual samples, BS CRM 12B, well agree with the corresponding certified values. Reproducibility of analytical values for minor and trace elements was within 3%, except for the 4.5% of boron.