Differentiation of monoepoxide isomers of polyunsaturated fatty acids and fatty acid esters by low-energy charge exchange mass spectrometry

Keough, T.; Mihelich, Edward D.; Eickhoff, David

doi:10.1021/ac00275a021

Cited by 12 publications

(4 citation statements)

References 25 publications

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“…Several methods have been developed, depending on the structure of the compound in questions. In the case of epoxides formed by oxidation of a terminal double bond, Elms allows an easy determination of the location (180) whereas in the case of monoepoxides obtained from polyunsaturated fatty acids, the determination is best performed by charge exchange mass spectrometry at low energy (181). Chemical ionization (with isobutane or nitric oxide) has also been used for the determination of the location of epoxide rings (182,183).…”

Section: Ivs22 Epoxidesmentioning

confidence: 99%

Acetogenins from Annonaceae

Cavé

Figadère

Laurens

et al. 1997

Fortschritte Der Chemie Organischer Naturstoffe Progress in the Chemistry of Organic Natural Products

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Section: Ivs22 Epoxidesmentioning

confidence: 99%

Acetogenins from Annonaceae

Cavé

Figadère

Laurens

et al. 1997

Fortschritte Der Chemie Organischer Naturstoffe Progress in the Chemistry of Organic Natural Products

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“…Use of differences in fragmentation patterns after collision-induced dissociation (CID) is still the most common and well-studied approach. 1À3,5À7,9,10 Other techniques exploit differences in physical properties of isomeric ions: migration rates of ions through a neutral gas (ion mobility spectrometry), 11,12 reactivities of ions, 13,14 charge exchange MS, 15,16 direct photon absorption or emission, 17,18 variable wavelength photodissociation in the infrared, 19À23 visible 24 or ultraviolet 25 with one or more 26,27 lasers, differences in photodissociation by rapid pulse shaping over an approximate Gaussian wavelength distribution centered at 800 nm, 28,29 and relatively high-resolution spectroscopy…”

mentioning

confidence: 99%

“…The problem has been approached in different ways, some more successful than others, depending on the nature of the precursor ions. Use of differences in fragmentation patterns after collision-induced dissociation (CID) is still the most common and well-studied approach. − ,− ,, Other techniques exploit differences in physical properties of isomeric ions: migration rates of ions through a neutral gas (ion mobility spectrometry), , reactivities of ions, , charge exchange MS, , direct photon absorption or emission, , variable wavelength photodissociation in the infrared, − visible or ultraviolet with one or more , lasers, differences in photodissociation by rapid pulse shaping over an approximate Gaussian wavelength distribution centered at 800 nm, , and relatively high-resolution spectroscopy in cold traps. , In cases relying on dissociation of a precursor ion, the mass spectra may be too similar to assign particular isomers from the product ion ratios with confidence. This can occur for several reasons: (1) product ion ratios frequently differ somewhat among different instruments; (2) product ion ratios can vary somewhat using the same instrument under supposedly identical conditions; (3) methods of processing digitized spectral data vary, and at least some error is introduced in quantitation of spectral peaks depending on the processing method; (4) white noise is present to varying extents; and (5) a proper statistical evaluation of data is often not performed.…”

mentioning

confidence: 99%

Differentiation of Closely Related Isomers: Application of Data Mining Techniques in Conjunction with Variable Wavelength Infrared Multiple Photon Dissociation Mass Spectrometry for Identification of Glucose-Containing Disaccharide Ions

et al. 2011

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Data mining algorithms have been used to analyze the infrared multiple photon dissociation (IRMPD) patterns of gas-phase lithiated disaccharide isomers irradiated with either a line-tunable CO(2) laser or a free electron laser (FEL). The IR fragmentation patterns over the wavelength range of 9.2-10.6 μm have been shown in earlier work to correlate uniquely with the asymmetry at the anomeric carbon in each disaccharide. Application of data mining approaches for data analysis allowed unambiguous determination of the anomeric carbon configurations for each disaccharide isomer pair using fragmentation data at a single wavelength. In addition, the linkage positions were easily assigned. This combination of wavelength-selective IRMPD and data mining offers a powerful and convenient tool for differentiation of structurally closely related isomers, including those of gas-phase carbohydrate complexes.

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“…This approach had utility for gleaning one-dimensional structural information. 8 Regarding sensitivity, in a recent study using membraneinterface mass spectrometry (MIMS) and an ion trap, charge-exchange ionization with solvent vapor led to ion currents even higher than those observed for EI in several cases. 9 Finally, it is generally appreciated that low-pressure CI using an ion trap can be at least as sensitive as electron ionization on the same instrument.…”

mentioning

confidence: 99%

Structure elucidation by ion trap sequential mass spectrometry of radical cations formed in low-energy charge-exchange reactions

Strife¹

1999

Rapid Commun. Mass Spectrom.

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A low-pressure, low-energy charge-exchange reaction with furan is shown to be a convenient method for generating the requisite intense ion signals from molecular radical cations of dextromethorphan for MS n (sequential, product-ion scans) analysis. Little fragmentation results, concentrating ion current in the molecular species and facilitating MS n probing. Results for the odd-electron species are shown to provide some unique information compared to electrospray ionization MS n of the even-electron, protonated molecule of dextromethorphan. Copyright # 1999 John Wiley & Sons, Ltd. Received 18 February 1999; Accepted 20 February 1999 Previously we have shown the direct structure elucidation of a surfactant in a complex aqueous mixture via sequential product ion analysis (so-called MS n ) using an ion trap. The mixture was analyzed via infusion with electrospray ionization (ESI), using the trap as a gas-phase purification device, followed by structural probing. 1 The main advantages of the MS n experiment compared to triple quadrupole MS/MS analyses were found to be: (1) complete definition of genealogical relationships of fragment ions, (2) cumulative energy deposition over several stages, giving more complete fragmentation, and (3) clear elucidation of informative minor pathways because of enhanced selectivity of later generation (n b 2) experiments.Our experience over the last four years has been that successful structure-elucidation MS n studies out to 6-10 generations are dependent on: (1) the production of an adequate current of pseudomolecular ions (i.e. some species indicative of the intact molecule whose structure is being probed) and (2) little initial fragmentation. Thus, ESI often meets these criteria for MS n studies. For example, when using the ESI positive ion mode, protonated, ammoniated or natriated molecules might be produced, depending on solvent selection. However, these species are all evenelectron ions and fragmentations are often dominated by even-electron, neutral losses. Since all ions can be classified as even or odd electron, it seemed logical that MS n studies of odd-electron species (i.e. molecular ions) might yield unique structural information via different fragmentation pathways (e.g. loss of radicals). Such studies would rely on the production of a high number density of molecular ions with little initial fragmentation (low internal vibrational energy). It is noted here that the term molecular ion most commonly refers to a radical species produced by removal or addition of an electron to a neutral molecule. However, for clarity in this report, the somewhat redundant molecular radical cation will be used.In order to produce the required intense ion signals from molecular radical cations for MS n studies, it is suggested that using a low-energy, charge-exchange reaction (LE-CHER) at low reagent gas pressure is a particularly viable approach for ion traps. The fundamental principles of charge exchange have been discussed by many authors [2][3][4][5] and will not be reiterated here, ...

show abstract

Differentiation of monoepoxide isomers of polyunsaturated fatty acids and fatty acid esters by low-energy charge exchange mass spectrometry

Cited by 12 publications

References 25 publications

Acetogenins from Annonaceae

Acetogenins from Annonaceae

Differentiation of Closely Related Isomers: Application of Data Mining Techniques in Conjunction with Variable Wavelength Infrared Multiple Photon Dissociation Mass Spectrometry for Identification of Glucose-Containing Disaccharide Ions

Structure elucidation by ion trap sequential mass spectrometry of radical cations formed in low-energy charge-exchange reactions

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