Characterization and Improvement of Signal Drift Associated with Electron Ionization Quadrupole Mass Spectrometry

• Published in: Analytical chemistry (Washington) Vol. 82; no. 15; pp. 6480 - 6486
• Main Authors: D’Autry, Ward, Wolfs, Kris, Yarramraju, Sitaramaraju, Schepdael, Ann Van, Hoogmartens, Jos, Adams, Erwin
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.08.2010
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; Gas chromatographic methods; Gases; General, instrumentation; Ion chromatography; Mass spectrometry; Oxygen - chemistry; Simulation; Software; Spectrometric and optical methods; Spectrometry, Mass, Electrospray Ionization - instrumentation; Spectrometry, Mass, Electrospray Ionization - methods; Stainless Steel; Volatilization; Performance evaluation; Electron impact ionization; Support; Ion beam; Instrumentation; Standard; Analyzer; Coatings; Quadrupole spectrometer; Chemical enrichment; Characterization; Degradation; Improvement; Signal; Quantitative analysis; Gold; Factor analysis; Stability; Ion source; Sample; Use; Plate; Gas chromatography; Adsorption; Stainless steel; Instability; Software; Technique; Detection; Mass spectrometry; Electron spectrometry
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac100780s

Quadrupole mass spectrometry with electron ionization (EI-QMS) is a very popular detection technique in combination with gas chromatography. It is deployed for the analysis of volatile and semivolatile analytes in many industry domains. Although a very important factor for quantitative analysis, little is known about the stability of ion source performance. Only a few papers and patents report possible signal instabilities due to sample adsorption, degradation, or insulating deposits on the hot stainless steel surface of the ion source. In this study, a conventional stainless steel ion source was used to investigate possible signal drifts. It was observed that the EI-QMS instrument indeed suffered from continuous signal instability. It was found that the key parts which are responsible for the signal instabilities are those that regulate the ion beam toward the mass analyzer: the repeller, exit plate, and focusing lenses. The voltage of the repeller was found to have a major influence on the signal stability. The surface of the repeller, exit plate, and focusing lenses was modified by applying a gold coating. It was demonstrated that the signal stability of the MS dramatically improved when using the gold-coated parts. The contribution of each part to the stability improvement was quantitatively determined and compared with the standard stainless steel source performance. It was assumed that the signal drift observed with the stainless steel EI source originated from charge buildup on the surfaces. This hypothesis was supported by software simulations.