Thermospray mass spectrometry of <i>N</i>‐methylcarbamates

Saar, Jacob; Salomon, Avraham

doi:10.1002/oms.1210250406

Cited by 13 publications

(6 citation statements)

References 13 publications

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“…The validity of this statement is curroborated by the fact that reported mass spectra of the carbamates, as obtained by the application of var ious ionization conditions (i.e., conven tional chemical ionization (Cl) [il -l7] and LCjMS interfacing . [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]), show large differences. This is illustrated by the data for carbofuran which are summarized in Table 1.…”

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Ion formation of N-Methyl carbamate pesticides in thermospray mass spectrometry: The effects of additives to the liquid chromatographic eluent and of the vaporizer temperature

Honing

Barceló

Baar

et al. 1994

J. Am. Soc. Mass Spectrom.

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The effects of three additives-ammonium acetate, ammonium formate, and nicotinic acid-to the liquid chromatographic (LC) eluent and of the vaporizer temperature on the ion formation of N-methyl carbamate pesticides in thermospray (TSP) mass spectrometry was investigated by using filament- or discharge-assisted ionization. Nineteen carbamates and 12 of their known environmental degradation products were used as model compounds. The additives cause a strong reduction in the abundance of the characteristic fragment ions [M + H - CH3NCO](+) and [M - H - CH3NCO](-) for some of the carbamates. The addition of nicotinic acid reduces the quasimolecular ion intensity and, in most cases, produces nicotinic acid adduct ions. The addition of ammonium acetate or ammonium formate increases the intensity of the quasimolecular ion and in most cases produces a base peak for the ammonium adduct ion. The combination of a suppression of fragmentation and an enhancement of quasimolecular ion formation produces an overall gain in sensitivity. As to more specific effects, the addition of the ammonium salts reduces the intensity of M(-•) with the chlorinated carbamate barban and suppresses the formation of "odd" adduct ions in the TSP mass spectra of most other carbamates. Monitoring the intensity of the fragment and the quasimolecular ion signal as a function of the probe stem temperature, and the related probe tip temperature, proved to be an easy method to study the thermal degradation of the carbamates. This monitoring procedure showed that methiocarb and its sulfone already suffer from thermal degradation at a stem temperature of 90°C and that these compounds will therefore present problems in quantitation with LC/TSP mass spectrometry.

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Ion formation of N-Methyl carbamate pesticides in thermospray mass spectrometry: The effects of additives to the liquid chromatographic eluent and of the vaporizer temperature

Honing

Barceló

Baar

et al. 1994

J. Am. Soc. Mass Spectrom.

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“…9 Recently, these compounds were analysed again under EI bombardment by Suzuki et al 10 In the course of the characterization of N-methylcarbamates, several chemical ionization techniques, such as NH 3 PCI, 11 CH 4 -PCI, 10-12 collisioninduced dissociation (CID) combined with CH 4 PCI 13 and CH 4 NCI 10,14 were employed for their analysis. Liquid chromatography combined with thermospray (TSP) mass spectrometry 15,16 and TSP-triple stage mass spectrometry 17 were also used for their characterization. Finally, atmospheric pressure ionization techniques were also evaluated for the mass spectral analysis of these pesticides.…”

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Analysis of aromatic pesticides by mass spectrometry. Advantage of plasma desorption over electron impact and NH3 or CH4 positive chemical ionization: the competitive formation of M+. and MH+ ions

Bourcier

Hoppilliard

Kargar

1997

Rapid Commun. Mass Spectrom.

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Electron impact (EI) using ionizing electrons of different kinetic energies, ammonia and methane positive chemical ionization (PCI) and plasma desorption (PD) mass spectrometry were used for the analysis of aryl pesticides of the carbamate and phenylurea families. Under PD conditions, competitive formation and decomposition of M+. and MH+ ions was observed. It is shown that PD spectra give more information than do EI or PCI spectra, confirming PD as a method of choice for the analysis of small polyfunctional molecules. Rules are given for the identification of these families of pesticides. A thermochemical desorption ionization model defines the conditions required for the observation of both M+. and MH+ ions. © 1997 John Wiley & Sons, Ltd.

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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.…”

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confidence: 99%

“…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 to enhance thermal fragmentation [5]. An increase of either the ion source or vaporizer temperature typically causes the dissociation of adduct ions, such as [1,5,18]. The [M + 59]+ adduct ion has been shown to be due to an impurity in the commercially available ammonium acetate [27].…”

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

Volmer

Levsen

Honing

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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Thermospray mass spectrometry of N‐methylcarbamates

Cited by 13 publications

References 13 publications

Ion formation of N-Methyl carbamate pesticides in thermospray mass spectrometry: The effects of additives to the liquid chromatographic eluent and of the vaporizer temperature

Ion formation of N-Methyl carbamate pesticides in thermospray mass spectrometry: The effects of additives to the liquid chromatographic eluent and of the vaporizer temperature

Analysis of aromatic pesticides by mass spectrometry. Advantage of plasma desorption over electron impact and NH3 or CH4 positive chemical ionization: the competitive formation of M+. and MH+ ions

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

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