Ammonia chemical ionization mass spectrometry

Westmore, John B.; Alauddin, Mian M.

doi:10.1002/mas.1280050403

Cited by 115 publications

(54 citation statements)

References 169 publications

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“…The technique is normally performed using methane, isobutane, or ammonia as the CI gas [33][34][35]. In those cases, protonated molecules and molecular fragments tend to dominate the positive ion chemical ionization mass spectra.…”

Section: Evidence For Chemical Ionizationmentioning

confidence: 99%

Chemical Ionization Mass Spectrometry Using Carbon Nanotube Field Emission Electron Sources

Radauscher

Keil

Wells

et al. 2015

J. Am. Soc. Mass Spectrom.

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Abstract. A novel chemical ionization (CI) source has been developed based on a carbon nanotube (CNT) field emission electron source. The CNT-based electron source was evaluated and compared with a standard filament thermionic electron source in a commercial explosives trace detection desktop mass spectrometer. This work demonstrates the first reported use of a CNT-based ion source capable of collecting CI mass spectra. Both positive and negative modes were investigated. Spectra were collected for a standard mass spectrometer calibration compound, perfluorotributylamine (PFTBA), as well as trace explosives including trinitrotoluene (TNT), Research Department explosive (RDX), and pentaerythritol tetranitrate (PETN). The electrical characteristics, lifetime at operating pressure, and power requirements of the CNT-based electron source are reported. The CNT field emission electron sources demonstrated an average lifetime of 320 h when operated in constant emission mode under elevated CI pressures. The ability of the CNT field emission source to cycle on and off can provide enhanced lifetime and reduced power consumption without sacrificing performance and detection capabilities.

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Section: Evidence For Chemical Ionizationmentioning

confidence: 99%

Chemical Ionization Mass Spectrometry Using Carbon Nanotube Field Emission Electron Sources

Radauscher

Keil

Wells

et al. 2015

J. Am. Soc. Mass Spectrom.

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“…Because modern commercial instrumentation for CI-MS does not directly measure reagent gas pressure in the source, conditions cannot be duplicated easily between instruments. More notoriously, isobutane is difficult to work with because it fouls the ion source more rapidly than methane and shortens the operative lifetime of electron filaments [15,[18][19][20]. Methane CI experiments can be reliably performed for weeks or perhaps months, but CI with isobutane causes the filament to fail within hours or days of use.…”

Section: Introductionmentioning

confidence: 99%

Isobutane Made Practical as a Reagent Gas for Chemical Ionization Mass Spectrometry

Newsome

Steinkamp

Giordano

2016

J. Am. Soc. Mass Spectrom.

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Abstract. As a reagent gas for positive-and negative-mode chemical ionization mass spectrometry (CI-MS), isobutane (i-C 4 H 10 ) produces superior analyte signal abundance to methane. Isobutane has never been widely adopted for CI-MS because it fouls the ion source more rapidly and produces positive CI spectra that are more strongly dependent on reagent gas pressure compared with methane. Isobutane was diluted to various concentrations in argon for use as a reagent gas with an unmodified commercial gas chromatograph-mass spectrometer. Analyte spectra were directly compared using methane, isobutane, and isobutane/argon mixtures. A mixture of 10% i-C 4 H 10 in argon produced twice the positive-mode analyte signal of methane, equal to pure isobutane, and reduced spectral dependence on reagent gas pressure. Electron capture negative chemical ionization using 1% i-C 4 H 10 in argon tripled analyte signal compared with methane and was reproducible, unlike pure isobutane. The operative lifetime of the ion source using isobutane/ argon mixtures was extended exponentially compared with pure isobutane, producing stable and reproducible CI signal throughout. By diluting the reagent gas in an inert buffer gas, isobutane CI-MS experiments were made as practical to use as methane CI-MS experiments but with superior analytical performance.

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“…The spectrum shows sizeable peaks at m/z 140 and 142, which at first glance could be ascribed to the [M + H + ] ions of the aminoxy compound. However, ammonia chemical ionization of secondary and tertiary alcohols may also lead to the formation of [M + NH 4 + ] adduct ions [14]. Therefore, the CI mass spectrum is also consistent with DBP-A having a molecular mass that matches that of the halohydrin 4-chloro-2-methylbutan-2-ol (M = 122/124).…”

Section: Identification Of the Disinfection By-products Dbp-a Dbp-bmentioning

confidence: 65%

Identification of Halohydrins as Potential Disinfection By‐Products in Treated Drinking Water

Jobst

Taguchi

Bowen

et al. 2011

International Journal of Spectroscopy

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In 2001, two potential disinfection by-products (DBPs) were tentatively identified as 1-aminoxy-1-chlorobutan-2-ol (DBP-A) and its bromo analogue (DBP-B) (Taguchi 2001). Subsequently it became clear, by consulting an updated version of the NIST database, that their mass spectra are close to those of the halohydrins 4-chloro-2-methylbutan-2-ol and 3-bromo-2-methylbutan-2-ol. To establish the structures of these DBPs, additional mass spectrometric experiments, including Fourier transform ion cyclotron resonance (FTICR), were performed on treated drinking water samples and authentic halohydrin standards. It appears that DBP-A is 3-chloro-2-methylbutan-2-ol and that DBP-B is its bromo analogue. DBP-B has been detected in ozonated waters containing bromide. Our study also shows that these DBPs can be laboratory artefacts, generated by the reaction of residual chlorine in the sample with 2-methyl-2-butene, the stabilizer in the CH 2 Cl 2 used for extraction. This was shown by experiments using CH 2 Cl 2 stabilized with deuterium labelled 2-methyl-2-butene. Quenching any residual chlorine in the drinking water sample with sodium thiosulfate minimizes the formation of these artefacts.

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Ammonia chemical ionization mass spectrometry

Cited by 115 publications

References 169 publications

Chemical Ionization Mass Spectrometry Using Carbon Nanotube Field Emission Electron Sources

Chemical Ionization Mass Spectrometry Using Carbon Nanotube Field Emission Electron Sources

Isobutane Made Practical as a Reagent Gas for Chemical Ionization Mass Spectrometry

Identification of Halohydrins as Potential Disinfection By‐Products in Treated Drinking Water

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