Secondary electrospray ionization

Lan, Jiayi; Blanco, Francisco Garcı́a; Vidal-de-Miguel, Guillermo; Zenobi, Renato

doi:10.1016/b978-0-12-819967-1.00012-8

Cited by 9 publications

(17 citation statements)

References 21 publications

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“…[1][2][3][4][5] In the positive potential mode, the source water is usually weakly acidified with formic acid in order to build up the concentration of ions in the solution phase. 6,7 According to molecular dynamics studies, 8 singly charged gas-phase ions are released from the tips of transient surface protrusions on the highly charged droplets as hydrated species H 3 O + (H 2 O) n (typically n = 10 to 20), which will lose H 2 O molecules until an equilibrium size (n) distribution is reached. It is the ion chemical reactions that occur between these cluster reagent ions and trace compounds introduced into the surrounding air/nitrogen that are the basis of a very sensitive analytical technique when coupled to a mass spectrometer.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of secondary electrospray ionization mass spectrometry to a range of volatile organic compounds: Ligand switching ion chemistry and the influence of Zspray™ guiding electric fields

Dryahina

Polášek

Smith

et al. 2021

Rapid Comm Mass Spectrometry

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Rationale Secondary electrospray ionization (SESI) is currently only semi‐quantitative. In the Zspray™ arrangement of SESI‐MS, the transfer of ions from near atmospheric pressure to a triple quadrupole is achieved by guiding electric fields that partially desolvate both reagent and analyte ions which must be understood. Also, to make SESI‐MS more quantitative, the mechanisms and the kinetics of the reaction processes, especially ligand switching reactions of hydrated hydronium reagent ions, H3O+(H2O)n, with volatile organic compound (VOC) molecules, need to be understood. Methods A modified Zspray™ ESI ion source operating at sub‐atmospheric pressure with analyte sample gas introduced via an inlet coaxial with the spray was used. Variation of the ion‐guiding electric fields was used to reveal the degree of desolvation of both reagent and analyte ions. The instrument sensitivity was determined for several classes of VOCs by introducing bag samples of suitably varying concentrations as quantified on‐line using selected ion flow tube MS. Results Electric field desolvation resulted in largely protonated VOCs, MH+, and their monohydrates, MH+H2O, and for some VOCs proton‐bound dimer ions, MH+M, were formed. There was a highly linear response of the ion signal to the measured VOC sample concentration, which provided the instrument sensitivities, S, for 25 VOCs. The startling results show very wide variations in S from near 0 to 1 for hydrocarbons, and up to 100, on a relative scale, for polar compounds such as monoketones and unsaturated aldehydes. Conclusions The complex ion chemistry occurring in the SESI ion source, largely involving gas‐phase ligand switching, results in widely variable sensitivities for different classes of VOCs. The sensitivity is observed to depend on the dipole moment and proton affinity of the analyte VOC molecule, M, and to decrease with the observed fraction of MH+H2O, but other yet unrecognized factors must play a significant role.

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Section: Introductionmentioning

confidence: 99%

Sensitivity of secondary electrospray ionization mass spectrometry to a range of volatile organic compounds: Ligand switching ion chemistry and the influence of Zspray™ guiding electric fields

Dryahina

Polášek

Smith

et al. 2021

Rapid Comm Mass Spectrometry

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“…Hill and colleagues in 2000 3 who used electrospray to ionize analyte molecules that are introduced into the surrounding ambient air. Subsequent work by R. Zenobi, P. Martinez-Lozano Sinues and their colleagues [4][5][6][7] applied SESI with mass spectrometry (SESI-MS) to detect trace compounds in exhaled breath, 8 realizing estimated sensitivities in the parts-per-trillion by volume (pptv) regime. This highly sensitive analytical technique is now being used in other applications and is attracting some attention.…”

Section: Introductionmentioning

confidence: 99%

“…In SESI-MS operated in the positive mode, with which the present study is concerned, the liquid is usually a very dilute aqueous solution of formic acid. 8,9 Charged nanodroplets evaporate very quickly from the electrospray into the air at near-atmospheric pressure to form positively charged ion clusters of the kind H 3 O + (H 2 O) n in an equilibrium distribution in n that depends on the temperature of the droplets/ambient air. 10 These primary reagent ions react with analyte molecules in the gas phase, as previously demonstrated by elegant experiments using D 2 O vapour in the SESI source air.…”

Section: Introductionmentioning

confidence: 99%

“…This highly sensitive analytical technique is now being used in other applications and is attracting some attention. In SESI‐MS operated in the positive mode, with which the present study is concerned, the liquid is usually a very dilute aqueous solution of formic acid 8,9 . Charged nanodroplets evaporate very quickly from the electrospray into the air at near‐atmospheric pressure to form positively charged ion clusters of the kind H 3 O + (H 2 O) n in an equilibrium distribution in n that depends on the temperature of the droplets/ambient air 10 .…”

Section: Introductionmentioning

confidence: 99%

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Reagent and analyte ion hydrates in secondary electrospray ionization mass spectrometry (SESI‐MS), their equilibrium distributions and dehydration in an ion transfer capillary: Modelling and experiments

Dryahina

Som

Smith

et al. 2021

Rapid Comm Mass Spectrometry

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Rationale Secondary electrospray ionization (SESI) in a water spray environment at atmospheric pressure involves the reactions of hydrated hydronium reagent ions, H3O+(H2O)n, with trace analyte compounds in air samples. Understanding the formation and dehydration of reagent and analyte ions is the foundation for meaningful quantification of trace compounds by SESI‐mass spectrometry (MS). Methods A numerical model based on gas‐phase ion thermochemistry is developed that describes equilibria in H3O+(H2O)n reagent cluster ion distributions and ligand switching reactions with polar NH3 molecules leading to equilibrated hydrated ammonium ions NH4+(H2O)m. The model predictions are compared with experimental results obtained using a cylindrical SESI source coupled to an ion‐trap mass spectrometer via a heated ion transfer capillary. Non‐polar isoprene, C5H8, was used to further probe the nature of the reagent ions. Results Equilibrium distributions of H3O+(H2O)n ions and their reactions with NH3 molecules have been characterized by the model in the near‐atmospheric pressure SESI source. NH3 analyte molecules displace H2O ligands from the H3O+(H2O)n ions at the collisional rate forming NH4+(H2O)m ions, which travel through the heated ion transfer capillary losing H2O molecules. The data for variable NH3 concentrations match the model predictions and the C5H8 test substantiates the notion of dehydration in the heated capillary. Conclusions Large cluster ions formed in the SESI region are dehydrated to H3O+(H2O)1,2,3 and NH4+(H2O)1,2 while passing through the heated capillary, and considerable diffusion losses also occur. This phenomenon is also predicted for other polar analyte molecules, A, that can undergo similar switching reactions, thus forming AH+ and AH+(H2O)m analyte ions.

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“…Over the last decade, secondary electrospray ionization (SESI) has emerged and has been widely used to ionize metabolites in the gas phase. Given its modularity [4], SESI can be coupled with various commercial mass spectrometers. Particularly attractive is the coupling to high-resolution mass spectrometers (HRMS), e.g.…”

Section: Introductionmentioning

confidence: 99%

Minimizing ion competition boosts volatile metabolome coverage by secondary electrospray ionization orbitrap mass spectrometry

Kaeslin¹,

Lan²,

Zenobi³

2020

Preprint

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Secondary electrospray ionization high-resolution mass spectrometry (SESI-HRMS) is an emerging technique for detection of volatile metabolites. However, reduced sensitivity and reproducibility of SESI-HRMS have limited its applications in untargeted metabolomics profiling. Ion suppression in the SESI source has been considered to be the main cause. Here, we show that besides ion suppression, ion competition in the detection process on Orbitrap instruments is another important factor influencing sensitivity and reproducibility of SESI-MS. Instead of acquiring the full m/z range, acquisition of consecutive m/z windows to minimize the ion competition effect allows the detection of many more robust features. Optimal m/z window ranges are proposed for measuring human breath and bacteria culture samples on SESI-Orbitrap MS, considering the balance for maximizing scanning speed and minimizing ion competition.

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Secondary electrospray ionization

Cited by 9 publications

References 21 publications

Sensitivity of secondary electrospray ionization mass spectrometry to a range of volatile organic compounds: Ligand switching ion chemistry and the influence of Zspray™ guiding electric fields

Sensitivity of secondary electrospray ionization mass spectrometry to a range of volatile organic compounds: Ligand switching ion chemistry and the influence of Zspray™ guiding electric fields

Reagent and analyte ion hydrates in secondary electrospray ionization mass spectrometry (SESI‐MS), their equilibrium distributions and dehydration in an ion transfer capillary: Modelling and experiments

Minimizing ion competition boosts volatile metabolome coverage by secondary electrospray ionization orbitrap mass spectrometry

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