Electron Ionization and Atmospheric Pressure Photochemical Ionization in Gas Chromatography-Mass Spectrometry Analysis of Amino Acids

Revelsky, I. A.; Yashin, Yuri S.; Sobolevsky, Tim; Revelsky, A. I.; Miller, Barbara; Oriedo, Vincent

doi:10.1255/ejms.581

Cited by 55 publications

(34 citation statements)

References 13 publications

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“…As an LC-MS interface, APPI has been applied widely in e.g., pharmaceutical, biological, and environmental analysis [3,4]. Although APPI was originally developed for LC-MS, there is also an increasing number of reports using it as an interface for GC-MS [5][6][7][8][9][10][11][12]. A major advantage of GC compared with LC is its much higher peak capacity, which allows the separation of a much higher number of compounds in one chromatographic run.…”

Section: Introductionmentioning

confidence: 99%

Ionization of EPA Contaminants in Direct and Dopant-Assisted Atmospheric Pressure Photoionization and Atmospheric Pressure Laser Ionization

Kauppila

Kersten

Benter

2015

J. Am. Soc. Mass Spectrom.

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Abstract. Seventy-seven EPA priority environmental pollutants were analyzed using gas chromatography-mass spectrometry (GC-MS) equipped with an optimized atmospheric pressure photoionization (APPI) and an atmospheric pressure laser ionization (APLI) interface with and without dopants. The analyzed compounds included e.g., polycyclic aromatic hydrocarbons (PAHs), nitro compounds, halogenated compounds, aromatic compounds with phenolic, acidic, alcohol, and amino groups, phthalate and adipatic esters, and aliphatic ethers. Toluene, anisole, chlorobenzene, and acetone were tested as dopants. The widest range of analytes was ionized using direct APPI (66/77 compounds). The introduction of dopants decreased the amount of compounds ionized in APPI (e.g., 54/77 with toluene), but in many cases the ionization efficiency increased. While in direct APPI the formation of molecular ions via photoionization was the main ionization reaction, dopant-assisted (DA) APPI promoted ionization reactions, such as charge exchange and proton transfer. Direct APLI ionized a much smaller amount of compounds than APPI (41/77 compounds), showing selectivity towards compounds with low ionization energies (IEs) and long-lived resonantly excited intermediate states. DA-APLI, however, was able to ionize a higher amount of compounds (e.g. 51/77 with toluene), as the ionization took place entirely through dopant-assisted ion/molecule reactions similar to those in DA-APPI. Best ionization efficiency in APPI and APLI (both direct and DA) was obtained for PAHs and aromatics with O-and N-functionalities, whereas nitro compounds and aliphatic ethers were the most difficult to ionize. Halogenated aromatics and esters were (mainly) ionized in APPI, but not in APLI.

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Section: Introductionmentioning

confidence: 99%

Ionization of EPA Contaminants in Direct and Dopant-Assisted Atmospheric Pressure Photoionization and Atmospheric Pressure Laser Ionization

Kauppila

Kersten

Benter

2015

J. Am. Soc. Mass Spectrom.

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“…Although APPI was originally developed as an interface for LC-MS, some gas chromatography-mass spectrometry (GC-MS) applications utilizing APPI have also emerged [9][10][11][12][13][14][15][16][17][18]. A general advantage of GC is its overwhelming separation efficiency compared with LC, and in particular for APPI the absence of LC solvents significantly enhances the charge exchange process between the dopant molecular ions and the neutral analyte.…”

Section: Introductionmentioning

confidence: 99%

The Ionization Mechanisms in Direct and Dopant-Assisted Atmospheric Pressure Photoionization and Atmospheric Pressure Laser Ionization

Kauppila

Kersten

Benter

2014

J. Am. Soc. Mass Spectrom.

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A novel, gas-tight API interface for gas chromatography-mass spectrometry was used to study the ionization mechanism in direct and dopant-assisted atmospheric pressure photoionization (APPI) and atmospheric pressure laser ionization (APLI). Eight analytes (ethylbenzene, bromobenzene, naphthalene, anthracene, benzaldehyde, pyridine, quinolone, and acridine) with varying ionization energies (IEs) and proton affinities (PAs), and four common APPI dopants (toluene, acetone, anisole, and chlorobenzene) were chosen. All the studied compounds were ionized by direct APPI, forming mainly molecular ions. Addition of dopants suppressed the signal of the analytes with IEs above the IE of the dopant. For compounds with suitable IEs or Pas, the dopants increased the ionization efficiency as the analytes could be ionized through dopant-mediated gas-phase reactions, such as charge exchange, proton transfer, and other rather unexpected reactions, such as formation of [M + 77](+) in the presence of chlorobenzene. Experiments with deuterated toluene as the dopant verified that in case of proton transfer, the proton originated from the dopant instead of proton-bound solvent clusters, as in conventional open or non-tight APPI sources. In direct APLI using a 266 nm laser, a narrower range of compounds was ionized than in direct APPI, because of exceedingly high IEs or unfavorable two-photon absorption cross-sections. Introduction of dopants in the APLI system changed the ionization mechanism to similar dopant-mediated gas-phase reactions with the dopant as in APPI, which produced mainly ions of the same form as in APPI, and ionized a wider range of analytes than direct APLI.

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“…20 Microchip APPI was reported to preferentially produce protonated pseudo-molecular ions for androgenic steroids. 5 In our experimental conditions, protonation seems to be dominant over radical cation formation.…”

Section: Data Analysis For Gc-hrms/msmentioning

confidence: 99%

Gas Chromatography-High Resolution Tandem Mass Spectrometry Using a GC-APPI-LIT Orbitrap for Complex Volatile Compounds Analysis

Lee¹,

Smith²,

Jun³

2012

Mass Spectrometry Letters

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A new approach of volatile compounds analysis is proposed using a linear ion trap Orbitrap mass spectrometer coupled with gas chromatography through an atmospheric pressure photoionization interface. In the proposed GC-HRMS/MS approach, direct chemical composition analysis is made for the precursor ions in high resolution MS spectra and the structural identifications were made through the database search of high quality MS/MS spectra. Successful analysis of a complex perfume sample was demonstrated and compared with GC-EI-Q and GC-EI-TOF. The current approach is complementary to conventional GC-EI-MS analysis and can identify low abundance co-eluting compounds. Toluene co-sprayed as a dopant through API probe significantly enhanced ionization of certain compounds and reduced oxidation during the ionization.

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Electron Ionization and Atmospheric Pressure Photochemical Ionization in Gas Chromatography-Mass Spectrometry Analysis of Amino Acids

Cited by 55 publications

References 13 publications

Ionization of EPA Contaminants in Direct and Dopant-Assisted Atmospheric Pressure Photoionization and Atmospheric Pressure Laser Ionization

Ionization of EPA Contaminants in Direct and Dopant-Assisted Atmospheric Pressure Photoionization and Atmospheric Pressure Laser Ionization

The Ionization Mechanisms in Direct and Dopant-Assisted Atmospheric Pressure Photoionization and Atmospheric Pressure Laser Ionization

Gas Chromatography-High Resolution Tandem Mass Spectrometry Using a GC-APPI-LIT Orbitrap for Complex Volatile Compounds Analysis

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