Improvement of analyte to interferent line intensity ratio in direct current glow discharge mass spectrometry

Abstract

Elemental analysis by quadrupole mass spectrometry with direct current powered glow discharge ion source has been improved for flat Cu samples. The line ratio of analyte to Ar-related interferents can be enhanced for several orders of magnitude when ion source geometry, ion extraction system and operating parameters are optimised quasi-simultaneously. Such an extreme improvement may partially be explained by different ion energy distributions depending on their origin: matrix and analytes, working gas, residual gases. Probably it is due to a synergistic effect of several processes needing further investigation.

Suppression of gas species signals in direct current glow discharge time-of-flight mass spectrometry

“…1(a) serves as an ion source for TOFMS. The anode body of the GD is at ground potential throughout its operation in contrast to the work of Oksenoid et al 7 The With an increase in discharge pressure, instrument in the ms-pulse GD mode in order to achieve good the intensities of the gas ions decrease significantly; in contrast, sputtering.10 Interestingly, it was found that the Macor disc the analyte signals reach a maximum when the pressure is can be omitted when the GD source works in the dc-GD 300 Pa and a good line intensity ratio of analyte to gas species mode. We suspect that such an experimental difference has a is obtained, after which the line intensities of the analyte close relationship with the plasma characteristics of dc-GD decrease with further increase in gas pressure.…”

“…source, because of the different energy distributions of gas species and analyte ions in the discharge. 5,6 In addition, the line intensity ratio of analyte to discharge gas in quadrupole dc-GDMS has also been improved by several orders of magni-Experimental tude by Oksenoid et al,7 and such a large enhancement was believed to be due to the different ion energy distributions Except for the modifications to the GD ion source, the ion optics depending on the origin of different ion species.7 However, in and the linear TOF mass analyzer utilized in this work were order to reach such a high performance, it is necessary to basically the same as those reported previously.10 Therefore, the optimize the ion source geometry, ion extraction system and emphasis here will be placed mainly on the GD ion source. operational parameters of GDMS quasi-simultaneously, which Throughout this work, a pure copper disc served as the sample makes the experimental procedure very complicated.7 cathode, and Ar (99.999%, Fuyou Gas Corporation, Xiamen, On the other hand, in the last few years, pulse-GDMS, China) was used as the working gas.…”