Solvent composition dependent signal reduction of molecular ions generated from aromatic compounds in (+) atmospheric pressure photoionization mass spectrometry

Lee, Seulgidaun; Ahmed, Arif; Kim, Sungjune

doi:10.1002/rcm.8127

Cited by 7 publications

(10 citation statements)

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“…44 Previous studies showed that chemical reactions such as charge transfer and/or proton transfer between solvent and analyte are important for APPI mechanism. [45][46][47] Therefore, there is a common element shared by PSCI, atmospheric pressure chemical ionization, and APPI mechanisms, and that can explain the improved ionization efficiency with chlorobenzene for both APPI and PSCI. It is notable that the data presented in Figure 4 show that the PSCI sensitivity does not strictly correlate with the dielectric constants.…”

Section: Resultsmentioning

confidence: 99%

Mechanism behind the paper spray chemical ionization phenomenon and the choice of solvent

et al. 2020

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Paper spray chemical ionization (PSCI) combined with mass spectrometry has been proposed as a sensitive method for the analysis of nonpolar aromatic compounds; however, the mechanism behind PSCI is not well understood. In the present study, the evidence for the occurrence of corona discharge is provided and its mechanism is proposed. Photographs taken with a highly sensitive camera evidently demonstrate the occurrence of corona discharge at the end of the triangular shape tip when a nonpolar solvent such as hexane was used at an applied potential of 6-7 kV.Nevertheless, corona discharge was not observed in the presence of a polar solvent.The occurrence of the corona discharge was attributed to charge accumulation in the dielectric layer generated by the nonpolar solvent on the fibers of the paper tip. Specifically, corona discharge was generated at the tip end when the charge approached a critical threshold. In the presence of a polar solvent, however, the dielectric layer was not generated and, hence, corona discharge was not observed. Based on this information, three nonpolar solvents were selected and their sensitivity for analyzing the phenanthrene and maltene fractions of crude oil was evaluated. Chlorobenzene provided the highest signal abundance; therefore, it was suggested as the optimum solvent for PSCI. Notably, the fundamental understanding of corona discharge in PSCI acquired in this study provides a basis for further improvement of this technique by way of surface modification.

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Section: Resultsmentioning

confidence: 99%

Mechanism behind the paper spray chemical ionization phenomenon and the choice of solvent

et al. 2020

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“…In addition, the signal intensities were observed to reduce by different extents for the three catechol isomers as methanol was introduced into the toluene, which is in good agreement with our previous study that showed a reduction in signal intensity when methanol was used as a co‐solvent with toluene in (+) APPI …”

Section: Resultsmentioning

confidence: 99%

“…[23][24][25][26] Many ionization techniques are used in LC/MS, among which atmospheric pressure photoionization (APPI), atmospheric pressure chemical ionization (APCI), and electrospray ionization (ESI) are most the common and popular. [27][28][29][30][31][32][33][34][35][36] Despite their identical molecular formulas, isomers exhibit different physical and chemical properties; however, their similarities make it difficult to explain some of their experimentally observed properties. For this reason, many studies aimed at understanding the APPI ionization mechanism have been conducted in order to better use this technique.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, APPI is the most popular selective technique for non‐polar or low‐polarity compounds; it is a very effective technique for the analysis of polyaromatic hydrocarbons (PAHs) because 10–10.6 eV photons are used in APPI to ionize the analyte molecule, and most PAHs have ionization energies below 10 eV. For this reason, many studies aimed at understanding the APPI ionization mechanism have been conducted in order to better use this technique …”

Section: Introductionmentioning

confidence: 99%

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Systematic Investigation into the Differences in the (+) APPI Efficiencies of Positional (Ortho, Meta, and Para) Isomers

Ahmed

Islam

Solihat

et al. 2019

Bulletin Korean Chem Soc

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Understanding the underlying principle behind the ionization technique is important for improving the sensitivity and selectivity of mass spectrometry (MS), and analyte-solvent interactions are important factors that affect the ionization process. In this study, analyte-solvent interactions were investigated using a series of ortho, meta, and para isomers, (+) APPI-MS, and computational chemistry. Experimental results reveal that isomers can have vastly different ionization efficiencies, despite their identical elemental formulas and functional groups. To better understand the reasons behind these observations, various analytesolvent radical-ion complexes were investigated by quantum mechanical techniques, and the factors that contribute to the differences in the ion-formation behavior of these compounds were thoroughly investigated.

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“…As a result, the revealed mechanisms behind the H-abstraction reactions occurring on PI source may provide illuminating insights into the H-abstraction fundamentals on EI source. On PI source, the hydrogen source for H-abstraction reactions is protic solvents used for injection, such as toluene, 29 water, 32 methanol, 33 ethanol and hexane. 28 Whereas aprotic solvents such as tetrachloromethane and aprotic gases including N2, O2 and CO2 could compete with analytes to abstract hydrogen atoms, thus impair the MS signal intensities of [M+H] + .…”

Section: Rh + [M] •+ → R • + [M+h] + (1)mentioning

confidence: 99%

Ascertaining Hydrogen-Abstraction Reaction Efficiencies of Halogenated Organic Compounds in Electron Impact Ionization Processes by Gas Chromatography–High-Resolution Mass Spectrometry

et al. 2020

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H-abstraction reactions occurring on electron ionization mass spectrometry (EI-MS) are a longstanding and crucial topic in MS research. Yet some critical relevant mechanisms are controversial and ambiguous, and information about the EI-induced H-abstraction reactions of halogenated organic compounds (HOCs) is completely in the dark. This study provides a systematic investigation of H-abstraction reactions of HOCs taking place on EI source using 13 C6-hexachlorobenzene ( 13 C6-HCB) and 13 C6-hexabromobenzene ( 13 C6-HBB) as exemplary compounds by gas chromatography high resolution mass spectrometry (GC-HRMS). The Habstraction efficiencies were evaluated with the MS signal intensity ratios of ions with Habstraction relative to the corresponding original ions (without H-abstraction). Ion source temperatures, EI energies and numbers of heavy isotope atoms ( 37 Cl or 81 Br) of isotopologues were investigated in terms of their effects on the H-abstraction efficiencies. The H-abstraction efficiencies of individual isotopologues generally decreased from the first to the last isotopologues of respective ions, and those of individual ions were different from each other, with the highest values of 0.017 and 0.444 for 13 C6-HCB and 13 C6-HBB, respectively. The overall H-abstraction efficiencies involving all measured ions of 13 C6-HCB and 13 C6-HBB were 0.004 and 0.128, respectively. With increasing ion source temperatures, the H-abstraction efficiencies firstly increased to a summit and then began to linearly decrease. EI energies and emission currents could impact the H-abstraction efficiencies, but showed no certain tendency.The H-abstraction reactions were inferred to belong to ion-molecule reactions, and the siloxanes bleeding from the GC column might be the hydrogen source. Some strategies were proposed Page 3 for eliminating or alleviating the interference triggered by the H-abstraction reactions on EI-MS in identification of halogenated organic pollutants (HOPs). Our findings provide a better understanding for the EI-induced H-abstraction reactions of HOCs, and may benefit identification of HOPs in environmental analysis, especially for novel HOPs. Keywords:Hydrogen-abstraction efficiencies; Halogenated organic compounds; Electron ionization mass spectrometry; Ion-molecule reactions; Chlorine and bromine isotope effects; Gas chromatography-high resolution mass spectrometry Up to now, reported studies concerning H-abstraction reactions on EI source mainly focused on quinones. 20,21 While halogenated organic compounds (HOCs), e.g., organochlorines and organobromines, may also abstract hydrogen atoms on EI source, in view of their lone electron pairs of halogen atoms (e.g., Cl and Br). HOCs are a large category of chemicals produced by both natural and anthropogenic activities, [35][36][37][38] and have been contributing enormous influences to human beings and the environment, in either positive or negative ways. [39][40][41][42][43] Many HOCs are persistent, bioaccumulative and toxic pollutants, such as polychlorinated...

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Solvent composition dependent signal reduction of molecular ions generated from aromatic compounds in (+) atmospheric pressure photoionization mass spectrometry

Cited by 7 publications

References 61 publications

Mechanism behind the paper spray chemical ionization phenomenon and the choice of solvent

Mechanism behind the paper spray chemical ionization phenomenon and the choice of solvent

Systematic Investigation into the Differences in the (+) APPI Efficiencies of Positional (Ortho, Meta, and Para) Isomers

Ascertaining Hydrogen-Abstraction Reaction Efficiencies of Halogenated Organic Compounds in Electron Impact Ionization Processes by Gas Chromatography–High-Resolution Mass Spectrometry

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