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The even-electron rule in electrospray mass spectra of pesticides.
Rapid Commun Mass Spectrom. 2007; 21(23):3855-68.RC

Abstract

A study of the fragmentation and ion formation of three major families of pesticides (including herbicides, insecticides, and fungicides) by liquid chromatography/time-of-flight mass spectrometry (LC/TOF-MS) and liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOF-MS) was carried out using positive electrospray ionization (ESI) and the results compared with those by gas chromatography (GC)/TOF-MS with electron ionization (EI) in order to test the validity of the even-electron rule in electrospray ionization. First, the majority of the fragmentations by positive ion ESI were even electron (EE) ions (93% of the fragment ions). Secondly, the formation of odd-electron (OE) fragment ions was greater with EI, where the fragment ions were present in a ratio of approximately 1:2 (35% OE ions and 65% EE ions). Thirdly, in-source collision-induced dissociation (CID) fragmentation by LC/TOF-MS and CID fragmentation in the collision cell by LC/Q-TOF-MS/MS resulted in 95% of the fragment ions being identical between the two types of fragmentation. As ESI in the positive ion mode yields an EE precursor ion (normally a protonated molecule), this commonly leads to EE fragment ions by elimination of molecules - a process called the even-electron rule. Neutral radical losses were less common in ESI but were common in the EI spectra of the same compounds. The structures that did lead to OE ions in ESI (exceptions to the even-electron rule approximately 7% of all ESI ions) favored electronegative radical losses in approximately the following order: .SO(2)CH(3), .NO(2), .CH(3), .Cl, .SCH(3), .CH(2)CH, and .OH.

Authors+Show Affiliations

University of Almeria, Department of Analytical Chemistry, Almeria, Spain. mthurman@ono.comNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

17985325

Citation

Thurman, E Michael, et al. "The Even-electron Rule in Electrospray Mass Spectra of Pesticides." Rapid Communications in Mass Spectrometry : RCM, vol. 21, no. 23, 2007, pp. 3855-68.
Thurman EM, Ferrer I, Pozo OJ, et al. The even-electron rule in electrospray mass spectra of pesticides. Rapid Commun Mass Spectrom. 2007;21(23):3855-68.
Thurman, E. M., Ferrer, I., Pozo, O. J., Sancho, J. V., & Hernandez, F. (2007). The even-electron rule in electrospray mass spectra of pesticides. Rapid Communications in Mass Spectrometry : RCM, 21(23), 3855-68.
Thurman EM, et al. The Even-electron Rule in Electrospray Mass Spectra of Pesticides. Rapid Commun Mass Spectrom. 2007;21(23):3855-68. PubMed PMID: 17985325.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The even-electron rule in electrospray mass spectra of pesticides. AU - Thurman,E Michael, AU - Ferrer,Imma, AU - Pozo,Oscar J, AU - Sancho,Juan V, AU - Hernandez,Felix, PY - 2007/11/7/pubmed PY - 2008/1/9/medline PY - 2007/11/7/entrez SP - 3855 EP - 68 JF - Rapid communications in mass spectrometry : RCM JO - Rapid Commun Mass Spectrom VL - 21 IS - 23 N2 - A study of the fragmentation and ion formation of three major families of pesticides (including herbicides, insecticides, and fungicides) by liquid chromatography/time-of-flight mass spectrometry (LC/TOF-MS) and liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOF-MS) was carried out using positive electrospray ionization (ESI) and the results compared with those by gas chromatography (GC)/TOF-MS with electron ionization (EI) in order to test the validity of the even-electron rule in electrospray ionization. First, the majority of the fragmentations by positive ion ESI were even electron (EE) ions (93% of the fragment ions). Secondly, the formation of odd-electron (OE) fragment ions was greater with EI, where the fragment ions were present in a ratio of approximately 1:2 (35% OE ions and 65% EE ions). Thirdly, in-source collision-induced dissociation (CID) fragmentation by LC/TOF-MS and CID fragmentation in the collision cell by LC/Q-TOF-MS/MS resulted in 95% of the fragment ions being identical between the two types of fragmentation. As ESI in the positive ion mode yields an EE precursor ion (normally a protonated molecule), this commonly leads to EE fragment ions by elimination of molecules - a process called the even-electron rule. Neutral radical losses were less common in ESI but were common in the EI spectra of the same compounds. The structures that did lead to OE ions in ESI (exceptions to the even-electron rule approximately 7% of all ESI ions) favored electronegative radical losses in approximately the following order: .SO(2)CH(3), .NO(2), .CH(3), .Cl, .SCH(3), .CH(2)CH, and .OH. SN - 0951-4198 UR - https://www.unboundmedicine.com/medline/citation/17985325/The_even_electron_rule_in_electrospray_mass_spectra_of_pesticides_ L2 - https://doi.org/10.1002/rcm.3271 DB - PRIME DP - Unbound Medicine ER -