Charge exchange mass spectra of trimethylsilyl ethers of biologically important compounds.  Analytical technique

Jelus, Barbara L.; Munson, Burnaby; Fenselau, Catherine

doi:10.1021/ac60342a056

Cited by 40 publications

(15 citation statements)

References 14 publications

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“…The use of NO/N2 mixtures to obtain "pseudo" electron impact mass spectra has been previously reported (8). In the case of dendrobatid alkaloids, the NO/N2 spectra (Figures 2,3) are similar to electron impact spectra (2).…”

Section: Resultsmentioning

confidence: 52%

Alkaloids from Dendrobatid Frogs: Structures of Two ω-Hydroxy Congeners of 3-Butyl-5-Propylindolizidine and Occurrence of 2,5-Disubstituted Pyrrolidines and a 2,6-Disubstituted Piperidine

Daly¹,

Spande²,

Whittaker³

et al. 1986

J. Nat. Prod.

104

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Forty alkaloids were detected and characterized from skin extracts of high- and low-elevation populations of the poison frog Dendrobates histrionicus from northwestern Colombia. Combined gc/ms with NH3 or ND3 in a chemical ionization mode detected protonated parent ions and determined the number of exchangeable NH and OH hydrogens. Six previously unknown dendrobatid alkaloids were characterized. Two were 2,5-disubstituted pyrrolidines, which included pyrrolidine 197B, a trans-2-butyl-5-pentylpyrrolidine, while a third was a 2,6-dipentylpiperidine. Indolizidines 239AB and 239CD had the same relative configuration as the parent alkaloid 223AB [(5E,9E)3-butyl-5-propylindolizidine] and contained, respectively, a omega-hydroxy group in the propyl or butyl side chain. The profiles of alkaloids in the new northern populations of D. histrionicus are typical of the species in containing a set of about eight histrionicotoxins, in marked contrast to a related species, Dendrobates lehmanni, which does not contain histrionicotoxins.

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Section: Resultsmentioning

confidence: 52%

Alkaloids from Dendrobatid Frogs: Structures of Two ω-Hydroxy Congeners of 3-Butyl-5-Propylindolizidine and Occurrence of 2,5-Disubstituted Pyrrolidines and a 2,6-Disubstituted Piperidine

Daly¹,

Spande²,

Whittaker³

et al. 1986

J. Nat. Prod.

104

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show abstract

“…Neopentane produces similar positive CI spectra to isobutane and doubles the electron filament lifetime [20] but is many times more expensive than isobutane to obtain at high purity. Dilution of deleterious analytical gases, including isobutane with inert gases, has been performed for CI [29][30][31][32], but the experiments were not constructed for isobutane to directly interact with an analyte. In the present research, a reagent gas mixture of isobutane diluted in argon produces positive CI and EC-NCI spectra of equal or better quality to pure isobutane.…”

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 additive was introduced to the reagent gas line in increasing increments until the prominent methane reagent ions m/e 17 and 29 decreased in intensity to less than 3 % of the total reagent gas spectrum. When mixed in this way with methane the reagent total reagent ion currents were for ammonia: m/e (%Z); 18 (78), 29 (l), 35 (10); for water: 19 (60), 29 (4), 37 (25), 55 (1); for methanol: 29 (3), 33 (60), 65 (23), 97 (7); for methyl ether: 29 (4), 45 (50), 46 (2), 47 (36), 61 (3), 93 (3). Under these conditions the reagent gas cluster ions were minimized so that, as far as possible, there was a single important reactant ion in the reagent gas spectrum.…”

Section: E X P E R I M E N T a Lmentioning

confidence: 99%

Hydrolysis, methanolysis and ammonolysis of dicarboxylic acids and methyl esters under conditions of chemical ionization mass spectrometry

Weinkam

Gál

1976

Org. Mass Spectrom.

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Chemical ionization mass spectra of dicarboxylic acids and methyl esters show fragmentation and unimolecular reactions with reagent gases water, methanol, ammonia and methyl ether, which differ from those observed with hydrocarbon reagents methane and isobutane. These reactions involve exchange of the reagent gas for water or methanol of the dicarboxyl compounds, as well as secondary exchange of both functions. An effort has been made to determine the mechanism of these reactions and to determine the structural requirements necessary for their occurrence.

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Charge exchange mass spectra of trimethylsilyl ethers of biologically important compounds. Analytical technique

Cited by 40 publications

References 14 publications

Alkaloids from Dendrobatid Frogs: Structures of Two ω-Hydroxy Congeners of 3-Butyl-5-Propylindolizidine and Occurrence of 2,5-Disubstituted Pyrrolidines and a 2,6-Disubstituted Piperidine

Alkaloids from Dendrobatid Frogs: Structures of Two ω-Hydroxy Congeners of 3-Butyl-5-Propylindolizidine and Occurrence of 2,5-Disubstituted Pyrrolidines and a 2,6-Disubstituted Piperidine

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

Hydrolysis, methanolysis and ammonolysis of dicarboxylic acids and methyl esters under conditions of chemical ionization mass spectrometry

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