Fragment‐molecule adduct formation from oxime carbamates during negative‐ion chemical ionization mass spectrometry

Lynn, Bert C.; Marbury, G. Dean; Tuschall, John R.

doi:10.1002/oms.1210231011

“…The conditions prevailing in the high-pressure chemical ionization source of a conventional mass spectrometer are such that, in addition to unimolecular reactions (e.g., ionization of the analyte molecule and fragmentation of the parent ion), bimolecular, collisional reactions may occur with some facility (I), producing ions that complicate the mass spectral analysis. Numerous examples of such collisional reactions have been reported for compounds whose spectra are acquired under electron capture negative chemical ionization (NCI) conditions (2)(3)(4)(5)(6)(7)(8)(9)(10)(11). Examples from the positive chemical ionization (PCI) mode are also known (12).…”

Section: Introductionmentioning

confidence: 99%

“…A well-known example is the reaction of C2H5+ from a hydrocarbon enhancement gas with analyte molecules to form the commonly detected [M + C2H5]+ adduct in PCI (I). Alternatively, both the fragment ion and the neutral molecule may be derived from the sample under analysis, giving rise to either anion adducts (10,11) or cation adducts (12). Such gas-phase reactions are presumed to be independent of the moderating enhancement gas.…”

Section: Introductionmentioning

confidence: 99%

Adduct ion formation in the methane-enhanced negative chemical ionization mass spectrometry of 2-(alkylthio)- and 2-alkoxy-s-triazines

Mattina¹,

Huang²,

Hayes³

1990

Anal. Chem.

7

0

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+ 25]" are observed at significant abundance In the highpressure, methane-enhanced, negative chemical Ionization (NCI) mass spectra of seven 2-(aikylthio)-s-tr1azlnes. Under the same experimental conditions an adduct ion at [ + 12]*" Is noted In the mass spectra of six 2-alkoxy-s-triazines. These adduct Ions are Interferences In the mass spectral analysis of these compounds. Detailed studies using methane-d4, ia02/CH4, and Ar as alternate NCI enhancement gases reveal that the species responsible for adduct ion formation originate from the methane gas. This was confirmed by high-resolution accurate mass measurements of the adduct ions. Colllslonally activated decomposition tandem mass spectrometry experiments were performed In an attempt to elucidate the structure of the adducts. The variation of the adduct Ion abundance as a function of sample pressure, emission current, repeUer voltage, and Ion source temperature Is also reported and possible mechanisms for the formation of the adduct Ions are examined.

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“…mobile phase [16,17], require adjustments to obtain the necessary limits of detection and reproducibility, Mass spectrometric investigations of carbamate pesticides via different types of TSP interfaces have been reported widely [1][2][3][4][5][6][7][18][19][20][21][22][23][24][25][26]. These studies, however, indicate that solitary protonated molecules and /or molecular ammonium adduct ions are formed by carbamates that provide no structural information.…”

mentioning

confidence: 99%

Comparative study of different thermospray interfaces with carbamate pesticides: Influence of the ion source geometry

Volmer

¹

,

Levsen

²

,

Honing

³

et al. 1995

J. Am. Soc. Mass Spectrom.

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Sixteen carbamate pesticides that belong to four chemical classes (oxime-N-methylcarbamates, aryl N-methylcarbamates, N-phenylcarbamates, and methyl esters of substituted carbamic acids) were investigated via three different commercially available thermospray interfaces and ion sources that exhibit wide differences in source geometry. Comparisons were made between the three interfaces with respect to ion formation and sensitivity of detection. Experimental parameters were standardized to obtain comparable experimental conditions. Very similar mass spectra for most carbamates were obtained that illustrate independence from the geometry of the ionization and desolvation chambers of the interfaces. These findings are in sharp contrast to several literature reports. However, thermally labile carbamates gave unsatisfactory results with regard to spectral compatibility between the interfaces. Such differences were due to thermally assisted hydrolysis reactions that occur in the vaporizer probe prior to ionization and reflect differences in the vaporizer designs. The study proves conclusively that comparable spectra can be obtained under thermospray with different interfaces and mass spectrometers.

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“…The study proves conclusively that comparable spectra can be obtained under thermosprar with different interfaces and mass spectrometers. {J Am Soc Mass Spectrom 1995, 6, 656-667 C urrently thermospray (TSP) has been used extensively as a liquid chromatography-mass spectrometry (LC-MS) interface for the determination of a wide range of chemical classes; for example, pesticides [1][2][3][4][5][6][7] mobile phase [16,17], require adjustments to obtain the necessary limits of detection and reproducibility, Mass spectrometric investigations of carbamate pesticides via different types of TSP interfaces have been reported widely [1][2][3][4][5][6][7][18][19][20][21][22][23][24][25][26]. These studies, however, indicate that solitary protonated molecules and /or molecular ammonium adduct ions are formed by carbamates that provide no structural information.…”

mentioning

confidence: 99%

Comparative study of different thermospray interfaces with carbamate pesticides: Influence of the ion source geometry

VOLMER¹,

LEVSEN²,

HONING³

et al. 1995

Journal of the American Society for Mass Spectrometry

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Sixteen carbamate pesticides that belong to four chemical classes (oxime-N-methylcarbamates, aryl N-methylcarbamates, N-phenylcarbamates, and methyl esters of substituted carbamic acids) were investigated via three different commercially available thermospray interfaces and ion sources that exh ibit wide differences in source geometry. Comparisons were made between the three interfaces with respect to ion formation and sensitivity of detection. Experimental parameters were standardized to obtain comparable experimental conditions. Very similar mass spectra for most carbamates were obtained that illustrate independence from the geometry of the ion ization and desolvation chambers of the interfaces. These findings are in sharp contrast to several literature reports. However, thermally labile carbamates ga ve unsatisfactory results with regard to spectral compatibility between the interfaces. Such differences were due to thermally assisted hydrolysis reactions that occur in the vaporizer probe prior to ionization and reflect di fferences in the vaporizer designs. The study proves conclusively that comparable spectra can be obtained under thermosprar with different interfaces and mass spectrometers. {J Am Soc Mass Spectrom 1995, 6, 656-667 C urrently thermospray (TSP) has been used extensively as a liquid chromatography-mass spectrometry (LC-MS) interface for the determination of a wide range of chemical classes; for example, pesticides [1][2][3][4][5][6][7] mobile phase [16,17], require adjustments to obtain the necessary limits of detection and reproducibility, Mass spectrometric investigations of carbamate pesticides via different types of TSP interfaces have been reported widely [1][2][3][4][5][6][7][18][19][20][21][22][23][24][25][26]. These studies, however, indicate that solitary protonated molecules and /or molecular ammonium adduct ions are formed by carbamates that provide no structural information. For an unambiguous identification of carbamates in environmental samples, several additional fragment ions are required for proof of presence. Several methods have been reported to increase the number of fragment ions ; for example, use of different ionization modes [1,6], postcolumn addition of adduct reagents [4,19] or increased operating temperatures of the TSP in terface

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Fragment‐molecule adduct formation from oxime carbamates during negative‐ion chemical ionization mass spectrometry

Cited by 14 publications

References 4 publications

Adduct ion formation in the methane-enhanced negative chemical ionization mass spectrometry of 2-(alkylthio)- and 2-alkoxy-s-triazines

Adduct ion formation in the methane-enhanced negative chemical ionization mass spectrometry of 2-(alkylthio)- and 2-alkoxy-s-triazines

Comparative study of different thermospray interfaces with carbamate pesticides: Influence of the ion source geometry

Comparative study of different thermospray interfaces with carbamate pesticides: Influence of the ion source geometry

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