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Qing Z, Xu Y, Yu L, Liu J, Huang X, Tang Z, Cheng P, Zeng J. Investigation of fragmentation behaviours of isoquinoline alkaloids by mass spectrometry combined with computational chemistry. Sci Rep 2020; 10:733. [PMID: 31959815 PMCID: PMC6970995 DOI: 10.1038/s41598-019-57406-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 12/23/2019] [Indexed: 11/24/2022] Open
Abstract
Isoquinoline alkaloids, which are one of the most important types of alkaloids, are extensively distributed in herbal medicines. However, systematic and comprehensive investigations of the fragmentation behaviours of isoquinoline alkaloids have rarely been reported. Therefore, the goal of the present study is to simultaneously investigate the collision-induced dissociation patterns and the corresponding mechanism of isoquinoline alkaloids by mass spectrometry (MS) combined with computations. Nineteen types of isoquinoline alkaloids (66 compounds) were used as references to identify the characteristic fragmentation behaviours by quadrupole time-of-flight mass spectrometry (Q-TOF/MS) in positive electrospray ionization (ESI) mode. These types of isoquinoline alkaloids were divided into three categories primarily by the characteristic [M-NHR1R2]+ (R1 and R2 represent the substituent groups of the N-atom) fragment ions. High- and low-abundance [M-NHR1R2]+ ions were observed respectively for type I (1–13) and type II (14–29) alkaloids, respectively; however, the characteristic fragments were not detected for type III alkaloids (30–66) because of the existence of a p-π conjugated system. Each type of alkaloid was further classified by its characteristic fragmentation patterns and fragment ions. In addition, isoquinoline alkaloid with vicinal methoxy and hydroxy, vicinal methoxy, methylenedioxy, methoxy, and quaternary N-methyl groups could form the characteristic fragments by the loss of CH3OH, CH4, CH2O or CO, CH3 and CO, and CH3 moieties, respectively. The mechanisms of some interesting fragmentation behaviours, such as the formation of [M-NH3]+ and [M-CH3]+ fragment ions, were further demonstrated by computational chemistry. These characteristic fragmentation behaviours and fragment ions of isoquinoline alkaloids provide a solid foundation for the rapid and high-efficiency structural elucidation of similar metabolites in plant-derived medicines.
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Affiliation(s)
- Zhixing Qing
- Hunan Key Laboratory of Traditional Chinese Veterinary Medicine, Hunan Agricultural University, Changsha, 410128, China.,College of Food Science and Technology, Hunan Agricultural University, Changsha, 410128, China
| | - Yuqin Xu
- Department of pharmacy, First Affiliated Hospital of Hunan University of Chinese Medicine, Changsha, 410007, China
| | - Liuyi Yu
- School of pharmacy, Hunan University of Chinese Medicine, Changsha, 410208, China
| | - Jinghong Liu
- Hunan Key Laboratory of Traditional Chinese Veterinary Medicine, Hunan Agricultural University, Changsha, 410128, China
| | - Xiuqiong Huang
- Hunan Key Laboratory of Traditional Chinese Veterinary Medicine, Hunan Agricultural University, Changsha, 410128, China
| | | | - Pi Cheng
- Hunan Key Laboratory of Traditional Chinese Veterinary Medicine, Hunan Agricultural University, Changsha, 410128, China.
| | - Jianguo Zeng
- Hunan Key Laboratory of Traditional Chinese Veterinary Medicine, Hunan Agricultural University, Changsha, 410128, China. .,Micolta Bioresource Inc., Changsha, 410005, China.
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Dator R, von Weymarn LB, Villalta PW, Hooyman CJ, Maertens LA, Upadhyaya P, Murphy SE, Balbo S. In Vivo Stable-Isotope Labeling and Mass-Spectrometry-Based Metabolic Profiling of a Potent Tobacco-Specific Carcinogen in Rats. Anal Chem 2018; 90:11863-11872. [PMID: 30086646 PMCID: PMC6644709 DOI: 10.1021/acs.analchem.8b01881] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), is a potent lung carcinogen that exerts its carcinogenic effects upon metabolic activation. The identification and quantitation of NNK metabolites could identify potential biomarkers of bioactivation and detoxification of this potent carcinogen and may be used to predict lung cancer susceptibility among smokers. Here, we used in vivo isotope-labeling and high-resolution-mass-spectrometry-based methods for the comprehensive profiling of all known and unknown NNK metabolites. The sample-enrichment, LC-MS, and data-analysis workflow, including a custom script for automated d0- d4- m/ z-pair-peak detection, enabled unbiased identification of numerous NNK metabolites. The structures of the metabolites were confirmed using targeted LC-MS2 with retention-time ( tR) and MS2-fragmentation comparisons to those of standards when possible. Eleven known metabolites and unchanged NNK were identified simultaneously. More importantly, our workflow revealed novel NNK metabolites, including 1,3-Diol (13), α-OH-methyl-NNAL-Gluc (14), nitro-NK- N-oxide (15), nitro-NAL- N-oxide (16), γ-OH NNAL (17), and three N-acetylcysteine (NAC) metabolites (18a-c). We measured the differences in the relative distributions of a panel of nitroso-containing NNK-specific metabolites in rats before and after phenobarbital (PB) treatment, and this served as a demonstration of a general strategy for the detection of metabolic differences in animal and cell systems. Lastly, we generated a d4-labeled NNK-metabolite mixture to be used as internal standards ( d4-rat urine) for the relative quantitation of NNK metabolites in humans, and this new strategy will be used to assess carcinogen exposure and ultimately to evaluate lung-cancer risk and susceptibility in smokers.
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Affiliation(s)
- Romel Dator
- Masonic Cancer Center, University of Minnesota, 2231 6th Street SE, Minneapolis, MN 55455
| | - Linda B. von Weymarn
- Masonic Cancer Center, University of Minnesota, 2231 6th Street SE, Minneapolis, MN 55455
| | - Peter W. Villalta
- Masonic Cancer Center, University of Minnesota, 2231 6th Street SE, Minneapolis, MN 55455
| | - Cory J. Hooyman
- Independent Consultant, 3732 Harriet Avenue S., Minneapolis, MN 55409
| | - Laura A. Maertens
- Masonic Cancer Center, University of Minnesota, 2231 6th Street SE, Minneapolis, MN 55455
| | - Pramod Upadhyaya
- Masonic Cancer Center, University of Minnesota, 2231 6th Street SE, Minneapolis, MN 55455
| | - Sharon E. Murphy
- Masonic Cancer Center, University of Minnesota, 2231 6th Street SE, Minneapolis, MN 55455
| | - Silvia Balbo
- Masonic Cancer Center, University of Minnesota, 2231 6th Street SE, Minneapolis, MN 55455
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Tandarić T, Vianello R. Design of Exceptionally Strong Organic Superbases Based on Aromatic Pnictogen Oxides: Computational DFT Analysis of the Oxygen Basicity in the Gas Phase and Acetonitrile Solution. J Phys Chem A 2018; 122:1464-1471. [DOI: 10.1021/acs.jpca.7b11945] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tana Tandarić
- Computational Organic Chemistry and Biochemistry Group, Rud̵er Bošković Institute, Zagreb 10000, Croatia
| | - Robert Vianello
- Computational Organic Chemistry and Biochemistry Group, Rud̵er Bošković Institute, Zagreb 10000, Croatia
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Zhang X, Bai X, Fang L, Jiang K, Li Z. Decarboxylative Coupling Reaction in ESI(-)-MS/MS of 4-Nitrobenzyl 4-Hydroxybenzoates: Triplet Ion-Neutral Complex-Mediated 4-Nitrobenzyl Transfer. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:940-943. [PMID: 26926444 DOI: 10.1007/s13361-016-1339-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 01/09/2016] [Accepted: 01/10/2016] [Indexed: 06/05/2023]
Abstract
In negative electrospray ionization mass spectrometry of 4-nitrobenzyl 4-hydroxybenzoates, a decarboxylation reaction, which was significantly promoted by the presence of a nitro group on the benzyl group, competed with radical elimination reactions. Density functional theory calculations indicated that decarboxylation of deprotonated 4-nitrobenzyl vanillate occurred via a radical route involving homolytic cleavage of the Cbenzyl-O bond to give a triplet ion-neutral complex, followed by decarboxylative coupling.
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Affiliation(s)
- Xiaoping Zhang
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China
- College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, 310014, China
| | - Xingfeng Bai
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China
| | - Liwen Fang
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China
| | - Kezhi Jiang
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China.
| | - Zuguang Li
- College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, 310014, China.
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Gackowska A, Przybyłek M, Studziński W, Gaca J. Formation of chlorinated breakdown products during degradation of sunscreen agent, 2-ethylhexyl-4-methoxycinnamate in the presence of sodium hypochlorite. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2016; 23:1886-97. [PMID: 26408113 PMCID: PMC4713459 DOI: 10.1007/s11356-015-5444-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 09/15/2015] [Indexed: 05/05/2023]
Abstract
In this study, a new degradation path of sunscreen active ingredient, 2-ethylhexyl-4-methoxycinnamate (EHMC) and 4-methoxycinnamic acid (MCA) in the presence of sodium hypochlorite (NaOCl), was discussed. The reaction products were detected using gas chromatography-mass spectrometry (GC-MS). Since HOCl treatment leads to more polar products than EHMC, application of polar extracting agents, dichloromethane and ethyl acetate/n-hexane mixture, gave better results in terms of chlorinated breakdown products identification than n-hexane. Reaction of EHMC with HOCl lead to the formation of C=C bridge cleavage products such as 2-ethylhexyl chloroacetate, 1-chloro-4-methoxybenzene, 1,3-dichloro-2-methoxybenzene, and 3-chloro-4-methoxybenzaldehyde. High reactivity of C=C bond attached to benzene ring is also characteristic for MCA, since it can be converted in the presence of HOCl to 2,4-dichlorophenole, 2,6-dichloro-1,4-benzoquinone, 1,3-dichloro-2-methoxybenzene, 1,2,4-trichloro-3-methoxybenzene, 2,4,6-trichlorophenole, and 3,5-dichloro-2-hydroxyacetophenone. Surprisingly, in case of EHMC/HOCl/UV, much less breakdown products were formed compared to non-UV radiation treatment. In order to describe the nature of EHMC and MCA degradation, local reactivity analysis based on the density functional theory (DFT) was performed. Fukui function values showed that electrophilic attack of HOCl to the C=C bridge in EHMC and MCA is highly favorable (even more preferable than phenyl ring chlorination). This suggests that HOCl electrophilic addition is probably the initial step of EHMC degradation.
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Affiliation(s)
- Alicja Gackowska
- Faculty of Chemical Technology and Engineering, University of Technology and Life Science, Seminaryjna 3, 85-326, Bydgoszcz, Poland
| | - Maciej Przybyłek
- Department of Physical Chemistry, Collegium Medicum, Nicolaus Copernicus University, Kurpińskiego 5, 85-950, Bydgoszcz, Poland.
| | - Waldemar Studziński
- Faculty of Chemical Technology and Engineering, University of Technology and Life Science, Seminaryjna 3, 85-326, Bydgoszcz, Poland
| | - Jerzy Gaca
- Faculty of Chemical Technology and Engineering, University of Technology and Life Science, Seminaryjna 3, 85-326, Bydgoszcz, Poland
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Zhang X, Zhu P, Zhang H, Li Z, Jiang K, Lee MR. The competing radical eliminations in the tandem mass spectrometry of the OH-deprotonated benzyl vanillate. JOURNAL OF MASS SPECTROMETRY : JMS 2015; 50:432-436. [PMID: 25800026 DOI: 10.1002/jms.3534] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 10/10/2014] [Accepted: 10/22/2014] [Indexed: 06/04/2023]
Affiliation(s)
- Xiaoping Zhang
- College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, 310014, China; Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, 311121, China
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Butler M, Cabrera GM. A mass spectrometry-based method for differentiation of positional isomers of monosubstituted pyrazine N-oxides using metal ion complexes. JOURNAL OF MASS SPECTROMETRY : JMS 2015; 50:136-144. [PMID: 25601685 DOI: 10.1002/jms.3506] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 09/05/2014] [Accepted: 09/10/2014] [Indexed: 06/04/2023]
Abstract
A series of 11 pairs of substituted pyrazine N-oxides, differing in the substituent position, were examined using electrospray ionization mass spectrometry (ESI-MS) in order to use spectra to assess the differentiation of positional isomers. For each compound, mass spectra were recorded with three different metal cations, namely calcium (II), copper (II) and aluminum (III), with characterization of the observed peaks. Differentiation between regioisomeric N-oxides has been achieved by comparison of the identity and relative intensities of the peaks originating from the adduct ions formed with the metal ions. Principal component analysis (PCA) has been employed to assist in the interpretation of the results obtained with each metal ion, exploring possible trends according to the nature and position of the substituent in the pyrazine N-oxide.
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Affiliation(s)
- Matías Butler
- Departamento de Química Orgánica, UMyMFOR-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 3° piso, C1428EHA, Buenos Aires, Argentina
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Despotović I, Vianello R. Engineering exceptionally strong oxygen superbases with 1,8-diazanaphthalene di-N-oxides. Chem Commun (Camb) 2014; 50:10941-4. [DOI: 10.1039/c4cc05125d] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
1,8-Diazanaphthalene di-N-oxides show extraordinary oxygen basicity, being almost entirely a consequence of a large strain-induced destabilization in neutral forms.
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Affiliation(s)
- Ines Despotović
- Quantum Organic Chemistry Group
- Ruđer Bošković Institute
- HR-10000 Zagreb, Croatia
| | - Robert Vianello
- Quantum Organic Chemistry Group
- Ruđer Bošković Institute
- HR-10000 Zagreb, Croatia
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Zhang X, Li F, Lv H, Wu Y, Bian G, Jiang K. On the origin of the methyl radical loss from deprotonated ferulic and isoferulic acids: electronic excitation of a transient structure. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2013; 24:941-948. [PMID: 23580242 DOI: 10.1007/s13361-013-0604-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 01/28/2013] [Accepted: 02/05/2013] [Indexed: 06/02/2023]
Abstract
Formation of radical fragments from even-electron ions is an exception to the "even-electron rule". In this work, ferulic acid (FA) and isoferulic acid (IFA) were used as the model compounds to probe the fragmentation mechanisms and the isomeric effects on homolytic cleavage. Elimination of methyl radical and CO2 are the two competing reactions observed in the CID-MS of [FA - H](-) and [IFA - H](-), of which losing methyl radical violates the "even-electron rule". The relative intensity of their product ions is significantly different, and thereby the two isomeric compounds can be differentiated by tandem MS. Theoretical calculations indicate that both the singlet-triplet gap and the excitation energy decrease in the transient structures, as the breaking C-O bond is lengthened. The methyl radical elimination has been rationalized as the intramolecular electronic excitation of a transient structure with an elongating C-O bond. The potential energy diagrams, completed by the addition of the energy barrier of the radical elimination, have provided a reasonable explanation of the different CID-MS behaviors of [FA - H](-) and [IFA - H](-).
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Affiliation(s)
- Xiaoping Zhang
- Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou 310012, China
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Vessecchi R, Emery FS, Lopes NP, Galembeck SE. Electronic structure and gas-phase chemistry of protonated α- and β-quinonoid compounds: a mass spectrometry and computational study. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2013; 27:816-824. [PMID: 23495028 DOI: 10.1002/rcm.6519] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 01/18/2013] [Accepted: 01/18/2013] [Indexed: 06/01/2023]
Abstract
RATIONALE The use of quinonoid compounds against tropical diseases and as antitumor agents has prompted the search for new naturally occurring and synthetic derivatives. Among these quinonoid compounds, lapachol and its isomers (α- and β-lapachone) serve as models for the synthesis of new compounds with biological activity, and the use of electrospray ionization tandem mass spectrometry (ESI-MS/MS) analysis as a tool to elucidate and characterize these products has furnished important information about these compounds. METHODS ESI-MS/MS analysis under collision-induced dissociation conditions was used to describe the fragmentation mechanisms for protonated 1,4-naphthoquinone, 1,2-naphthoquinone, α-lapachone, and β-lapachone. The B3LYP/6-31+G(d,p) model was used to obtain proton affinities, gas-phase basicities, and molecular electrostatic potential maps, thus indicating the probable protonation sites. Fragmentation pathways were suggested on the basis of the relative enthalpies of the product ions. RESULTS The ESI-MS signals of the cationized molecules of ortho quinonoid compounds were more intense than those of the protonated molecule. Formation of the major product ions with m/z 187 from protonated α- and β-lapachone has been attributed to a retro-Diels-Alder (RDA) reaction. CONCLUSIONS MS/MS studies on lapachol isomers (α- and β-lapachone) will facilitate the interpretation of the liquid chromatography (LC)-MS/MS analysis of new metabolites. MS/MS data on the 1,4-naphthoquinone, 1,2-naphthoquinone, α-lapachone and β-lapachone core will help characterize new derivatives from in vitro/in vivo metabolism studies in complex matrices. The product ions revealed the major fragmentation mechanisms and these ions will serve as diagnostic ions to identify each studied compound.
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Affiliation(s)
- Ricardo Vessecchi
- Núcleo de Pesquisa em Produtos Naturais e Sintéticos, Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Brasil.
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11
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Vessecchi R, Tomaz JC, dos Santos GP, de Oliveira ARM, Lopes NP, Clososki GC. Gas-phase reactivity of protonated 2-oxazoline derivatives: mass spectrometry and computational studies. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2012; 26:1061-1069. [PMID: 22467456 DOI: 10.1002/rcm.6182] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
RATIONALE Oxazolines have attracted the attention of researchers worldwide due to their versatility as carboxylic acid protecting groups, chiral auxiliaries, and ligands for asymmetric catalysis. Electrospray ionization tandem mass spectrometric (ESI-MS/MS) analysis of five 2-oxazoline derivatives has been conducted, in order to understand the influence of the side chain on the gas-phase dissociation of these protonated compounds under collision-induced dissociation (CID) conditions. METHODS Mass spectrometric analyses were conducted in a quadrupole time-of-flight (Q-TOF) spectrometer fitted with electrospray ionization source. Protonation sites have been proposed on the basis of the gas-phase basicity, proton affinity, atomic charges, and a molecular electrostatic potential map obtained on the basis of the quantum chemistry calculations at the B3LYP/6-31 + G(d,p) and G2(MP2) levels. RESULTS Analysis of the atomic charges, gas-phase basicity and proton affinities values indicates that the nitrogen atom is a possible proton acceptor site. On the basis of these results, two main fragmentation processes have been suggested: one taking place via neutral elimination of the oxazoline moiety (99 u) and another occurring by sequential elimination of neutral fragments with 72 u and 27 u. These processes should lead to formation of R(+). CONCLUSIONS The ESI-MS/MS experiments have shown that the side chain could affect the dissociation mechanism of protonated 2-oxazoline derivatives. For the compound that exhibits a hydroxyl at the lateral chain, water loss has been suggested to happen through an E2-type elimination, in an exothermic step.
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Affiliation(s)
- Ricardo Vessecchi
- Núcleo de Pesquisa em Produtos Naturais e Sintéticos, Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil.
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Butler M, Mañez PA, Cabrera GM. Differentiation of isomeric hydroxypyridine N-oxides using metal complexation and electrospray ionization mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2011; 22:545-556. [PMID: 21472573 DOI: 10.1007/s13361-010-0059-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Revised: 11/27/2010] [Accepted: 11/29/2010] [Indexed: 05/30/2023]
Abstract
Differentiation between two isomers of hydroxypyridine N-oxide according to the metal cation adducts generated by electrospray ionization (ESI) was investigated for different metal cations, namely Mg(II), Al(III), Ca(II), Sc(III), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ga(III), besides the diatomic cation VO(IV). Protonated molecules of the isomeric hydroxypyridine N-oxides as well as the singly/doubly charged adducts formed from neutral or deprotonated ligands and a doubly/triply charged cation were produced in the gas phase using ESI, recording mass spectra with different metal ions for each isomer. While complex formation was successful for 2-hydroxypyridine N-oxide with trivalent ions, in the case of 3-hydroxypyridine N-oxide, only peaks related to the protonated molecule were present. On the other hand, divalent cations formed specific species for each isomer, giving characteristic spectra in every case. Hence, differentiation was possible irrespective of the metal cation utilized. In addition, quantum chemical calculations at the B3LYP/6-31+G(d,p) level of theory were performed in order to gain insight into the different complexation of calcium(II) with the isomers of hydroxypyridine N-oxide. The relative stability in the gas phase of the neutral complexes of calcium made up of two ligands, as well as the singly charged and doubly charged complexes, was investigated. The results of these calculations improved the understanding of the differences observed in the mass spectra obtained for each isomer.
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Affiliation(s)
- Matias Butler
- Departamento de Química Orgánica, UMyMFOR-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires., Ciudad Universitaria Pabellón II, 3° piso, C1428EHA, Buenos Aires, Argentina
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Sridhar L, Karthikraj R, Murty MRVS, Raju NP, Vairamani M, Prabhakar S. Mass spectral analysis of N-oxides of Chemical Weapons Convention related aminoethanols under electrospray ionization conditions. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2011; 25:533-542. [PMID: 21259362 DOI: 10.1002/rcm.4879] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
N,N'-Dialkylaminoethanols are the hydrolyzed products or precursors of chemical warfare agents such as V-agents and nitrogen mustards, and they are prone to undergo oxidation in environmental matrices or during decontamination processes. Consequently, screening of the oxidized products of aminoethanols in aqueous samples is an important task in the verification of chemical weapons convention-related chemicals. Here we report the successful characterization of the N-oxides of N,N'-dialkylaminoethanols, alkyl diethanolamines, and triethanolamine using positive ion electrospray ionization mass spectrometry. The collision-induced dissociation (CID) spectra of the [M+H](+) and [M+Na](+) ions show diagnostic product ions that enable the unambiguous identification of the studied N-oxides, including those of isomeric compounds. The proposed fragmentation pathways are supported by high-resolution mass spectrometry data and product/precursor ion spectra. The CID spectra of [M+H](+) ions included [MH-CH(4)O(2)](+) as the key product ion, in addition to a distinctive alkene loss that allowed us to recognize the alkyl group attached to the nitrogen. The [M+Na](+) ions show characteristic product ions due to the loss of groups (R) attached to nitrogen either as a radical (R) or as a molecule [R+H or (R-H)] after hydrogen migration.
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Affiliation(s)
- L Sridhar
- National Centre for Mass Spectrometry, Indian Institute of Chemical Technology, Hyderabad 500 607, A.P., India
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