Cold Electron Ionization (EI) Is Not a Supplementary Ion Source to Standard EI. It is a Highly Superior Replacement Ion Source

Amirav, Aviv; Fialkov, Alexander B.; Gordin, Alexander; Elkabets, Oneg; Eren, Ksenia J. Margolin

doi:10.1021/jasms.1c00241

Cited by 12 publications

(11 citation statements)

References 13 publications

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“…However, EI fragment spectra are often preferred over CID due to better reproducibility, platform independence, and availability of comprehensive libraries. Though examples for nontargeted analysis with GC-EI-MS are available in the literature, identification of the molecular ion, greatly facilitating compound assignment, is often not feasible due to extensive fragmentation immediately following the 70 eV ionization process; a complementary ionization mechanism yielding the molecular ion would therefore be desirable. , Numerous examples for “softer” ionization processes in a low-pressure ionization GC–MS system, for example, chemical- (CI), , photo- (PI), , field- (FI), , and cold electron ionization, , have been introduced. All these techniques generate intact molecular ions.…”

Section: Introductionmentioning

confidence: 99%

Parallel Operation of Electron Ionization and Chemical Ionization for GC–MS Using a Single TOF Mass Analyzer

et al. 2022

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This work describes a novel mass spectrometer coupled to gas chromatography (GC–MS) that simultaneously displays the mass spectral information of electron (EI)- and chemical ionization (CI)-generated ion populations for a single chromatographic peak. After GC separation, the eluent is equally split and supplied in parallel to an EI and a novel CI source, both operating continuously. Precise switching of the ion optics provides the exact timing to consecutively extract the respective ion population from both sources and transfer them into a time-of-flight (TOF) mass analyzer. This technique enables the acquisition of complementary information from both ion populations (EI and CI) within a single chromatographic run and with sufficient data points to retain the chromatographic fidelity. The carefully designed GC transfer setup, fast ion optical switching, and synchronized TOF data acquisition system provide an automatic and straightforward spectral alignment of two ion populations. With an eluent split ratio of about 50% between the two ion sources, instrument detection limits of <40 fg on the column (octafluoronaphthalene) for the EI and <2 pg (benzophenone) for the CI source were obtained. The system performance and the additional analytical value for compound identification are demonstrated by means of different common GC standard mixtures and a commercial perfume sample of unknown composition.

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Section: Introductionmentioning

confidence: 99%

Parallel Operation of Electron Ionization and Chemical Ionization for GC–MS Using a Single TOF Mass Analyzer

et al. 2022

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“…Consequently, we conclude that Cold EI is not a supplementary ion source to standard EI. It is a highly superior replacement ion source 16 …”

Section: Discussionmentioning

confidence: 99%

“…Cold EI was developed by Amirav and his group in 1990, 2,3 it is reviewed in, 4,5 a book on GC–MS with Cold EI was recently published 6 and its features and applications were published in several papers 7–16 . GC–MS with Cold EI is based on interfacing the GC and MS with SMBs along with electron ionization of vibrationally cold sample molecules in the SMB (hence the name Cold EI) in a dual cage fly‐through ion source 17 .…”

Section: Introductionmentioning

confidence: 99%

“…Cold EI was developed by Amirav and his group in 1990, 2,3 it is reviewed in, 4,5 a book on GC-MS with Cold EI was recently published 6 and its features and applications were published in several papers. [7][8][9][10][11][12][13][14][15][16] GC-MS with Cold EI is based on interfacing the GC and MS with SMBs along with electron ionization of vibrationally cold sample molecules in the SMB (hence the name Cold EI) in a dual cage fly-through ion source. 17 Cold EI improves all the central performance aspects of GC-MS including enhanced abundance of molecular ions, improved sample identification, significantly extended range of compounds amenable for analysis, uniform response to all analytes, faster analysis, greater selectivity, higher S/N ratios, and lower LOD.…”

Section: Introductionmentioning

confidence: 99%

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Sensitivity comparison of gas chromatography–mass spectrometry with Cold EI and standard EI

Amirav

Yakovchuk

2023

J Mass Spectrom

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Gas chromatography–mass spectrometry (GC–MS) with Cold EI is based on interfacing GC and MS with supersonic molecular beams (SMBs) along with electron ionization of vibrationally cold sample compounds in SMB in a fly‐through ion source (hence the name Cold EI). Cold EI improves all the central performance aspects of GC–MS, and in this paper, we focus on its improvement of signal‐to‐noise ratio (S/N) and limits of detection (LODs). We found that the harder the compound for analysis with standard EI, the greater the Cold EI gain in S/N and LOD. The lower LOD and higher S/N of Cold EI emerge from a few reasons: (a) similar ionization yield as standard EI, (b) enhanced abundance of molecular ions, (c) elimination of vacuum background noise, (d) elimination of ion source‐related peak tailing and degradation, (e) ability to lower the elution temperatures via the use of high column flow rates, and (f) greater range of thermally labile and low‐volatility compounds that can be analyzed. We demonstrate the superior S/N and lower LOD of Cold EI versus standard EI in a range of compounds, from the simple‐to‐analyze octafluoronaphthalene all the way to reserpine and an organo‐metallic compound that cannot be analyzed by standard EI. These compounds include methyl stearate, cholesterol, n‐C32H66, large polycyclic aromatic hydrocarbons, dioctyl phthalates, diundecyl phthalate, pentachlorophenol, benzidine, lambda‐cyhalothrin, and methidathion. The significantly lower Cold EI LODs that can be over 1000 times better than in standard EI further result in far superior response linearity and greater measurement dynamic range.

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“…Cold-EI produces conventional EI mass spectra with improved molecular ions, enhancing the detectability and identification capabilities. Besides, Cold-EI possesses a wide range of analyzable compounds, including heavier molecules, and can also reduce ion source-related degradation or peak tailing problems [65].…”

Section: Lc-ei-ms Coupling: Interface Development and Advancesmentioning

confidence: 99%

Electron ionization mass spectrometry: Quo vadis?

et al. 2022

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Mass spectrometry (MS) is a fundamental technique to identify compounds by their mass-to-charge ratio. It is known that MS can only detect target compounds when they are converted to ions in the gas phase. The ionization procedure is considered one of the most critical steps, and there are distinct techniques for it. One of them is electron ionization (EI), a widely used hard-ionization technique capable of generating several ions due to the excess energy employed. The existence of distinct ionization mechanisms turns EI capable of producing a fingerprintlike spectrum for each molecule. So, it is an essential technique for obtaining structural information. EI is often combined with chromatography to obtain a practical introduction of pretreated samples despite its excellent performance. EI-MS has been applied coupled with gas chromatography (GC) since the 1960s as both are very compatible. Currently, analytes of interest are more suitable for liquid chromatography (LC) analysis, so there are researchers dedicated to developing suitable interfaces for coupling LC and EI-MS. EI excels, as a reliable technique to fill the gap between GC and LC, possibly allowing them to coexist in a single instrument. In this work, the authors will present the fundamentals of EI-MS, emphasizing the development over the years, coupling with gas and LC, and future trends.

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Cold Electron Ionization (EI) Is Not a Supplementary Ion Source to Standard EI. It is a Highly Superior Replacement Ion Source

Cited by 12 publications

References 13 publications

Parallel Operation of Electron Ionization and Chemical Ionization for GC–MS Using a Single TOF Mass Analyzer

Parallel Operation of Electron Ionization and Chemical Ionization for GC–MS Using a Single TOF Mass Analyzer

Sensitivity comparison of gas chromatography–mass spectrometry with Cold EI and standard EI

Electron ionization mass spectrometry: Quo vadis?

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