Atmospheric-pressure ionization mass-spectrograph apparatus

Abstract

Inside a first-stage intermediate vacuum chamber (6) of an atmospheric-pressure ionization mass-spectrograph apparatus, cluster ions that are the cause of background noise are generated mainly at area (A), and fragment ions are generated mainly at area (B). Accordingly, in cases of in-source CID analysis mode, a DC voltage that is lower than that of a skimmer (8) is applied to a first ion guide (7), so that an accelerating electric field is generated at area (B). This enables sufficient energy to be given to the ions, to facilitate fragmentation. In cases when in-Source CID analysis is not conducted, a DC voltage that is lower than that of the first ion guide (7) is applied to the exit end (3b) of a desolvation tube (3), so that no electric field is generated at area (B) and an accelerating electric field is generated only at area (A). This enables inhibition of generation of both the cluster ions and the fragment ions, and attainment of a high-quality chromatogram.

Description

technical field [0001] The present invention relates to an atmospheric pressure ionization mass spectrometer, which, like a liquid chromatography mass spectrometer, ionizes a liquid sample in an approximately atmospheric pressure environment and performs mass analysis in a high vacuum environment. Background technique [0002] In liquid chromatography-mass spectrometry (LC / MS), which combines a liquid chromatograph (LC) and a mass spectrometer (MS), in order to generate gas ions from a liquid sample, the electrospray ionization method ( Atmospheric pressure ion sources obtained by ESI), atmospheric pressure chemical ionization (APCI), etc. In an atmospheric pressure ionization mass spectrometer using such an atmospheric pressure ion source, the ionization chamber where ions are generated is in a substantially atmospheric pressure environment, and the analysis chamber equipped with a mass analyzer such as a quadrupole mass filter and a detector must maintain a high vacuum sta...

AI Technical Summary

Problems solved by technology

When cluster ions are generated, undesired peaks appear in the mass spectrum, and the peak pattern of the mass spectrum becomes complicated, which hinders the analysis

In addition, there are also cases where the ions obtained by sampling combine with mobile phase solvent molecules along with adiabatic expansion, thereby not only complicating the peak pattern of the mass spectrum, but also generating dimers and trimers of mobile phase solvent ions. bodies, etc., which become background noise, causing degradation of the chromatogram

[0008] In existing atmospheric pressure ionization mass spectrometers, the influence of background noise caused by cluster ions, etc., generated in the first-stage intermediate vacuum chamber is hardly considered as described above, and no attempt is made to actively reduce such noise

In particular, when the voltage applied to each electrode is adjusted so that the intensity of the target ions is maximized for in-source CID, even if the dissociation efficiency is good, the amount of simultaneously generated cluster ions is often relatively large. state, therefore, the quality of mass spectrometry and chromatogram is degraded, and it may be difficult to perform qualitative analysis and structural analysis of the target substance

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