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Liu Y, Wang X, Zhang D, Wang C, Xie H, Chen H, Chai Y. Does deprotonated benzoic acid lose carbon monoxide in collision-induced dissociation? JOURNAL OF MASS SPECTROMETRY : JMS 2024; 59:e4990. [PMID: 38146124 DOI: 10.1002/jms.4990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2023] [Revised: 10/25/2023] [Accepted: 11/09/2023] [Indexed: 12/27/2023]
Abstract
Decarboxylation is known to be the major fragmentation pathway for the deprotonated carboxylic acids in collision-induced dissociation (CID). However, in the CID mass spectrum of deprotonated benzoic acid (m/z 121) recorded on a Q-orbitrap mass spectrometer, the dominant peak was found to be m/z 93 instead of the anticipated m/z 77. Based on theoretical calculations, 18 O-isotope labeling and MS3 experiments, we demonstrated that the fragmentation of benzoate anion begins with decarboxylation, but the initial phenide anion (m/z 77) can react with trace O2 in the mass analyzer to produce phenolate anion (m/z 93) and other oxygen-containing ions. Thus oxygen adducts should be considered when annotating the MS/MS spectra of benzoic acids.
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Affiliation(s)
- Yingying Liu
- Tea Research Institute, Chinese Academy of Agricultural Sciences, Laboratory of Quality and Safety Risk Assessment for Tea Products (Hangzhou), Ministry of Agriculture and Rural Affairs, Hangzhou, China
- Graduate School of Chinese Academy of Agricultural Sciences, Beijing, China
| | - Xue Wang
- Tea Research Institute, Chinese Academy of Agricultural Sciences, Laboratory of Quality and Safety Risk Assessment for Tea Products (Hangzhou), Ministry of Agriculture and Rural Affairs, Hangzhou, China
- Graduate School of Chinese Academy of Agricultural Sciences, Beijing, China
| | - Danyang Zhang
- Tea Research Institute, Chinese Academy of Agricultural Sciences, Laboratory of Quality and Safety Risk Assessment for Tea Products (Hangzhou), Ministry of Agriculture and Rural Affairs, Hangzhou, China
| | - Chen Wang
- Tea Research Institute, Chinese Academy of Agricultural Sciences, Laboratory of Quality and Safety Risk Assessment for Tea Products (Hangzhou), Ministry of Agriculture and Rural Affairs, Hangzhou, China
| | - Haijiao Xie
- Hangzhou Yanqu Information Technology Co., Ltd., Hangzhou, China
| | - Hongping Chen
- Tea Research Institute, Chinese Academy of Agricultural Sciences, Laboratory of Quality and Safety Risk Assessment for Tea Products (Hangzhou), Ministry of Agriculture and Rural Affairs, Hangzhou, China
| | - Yunfeng Chai
- Tea Research Institute, Chinese Academy of Agricultural Sciences, Laboratory of Quality and Safety Risk Assessment for Tea Products (Hangzhou), Ministry of Agriculture and Rural Affairs, Hangzhou, China
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Liang Y, Simón-Manso Y, Neta P, Stein SE. Unexpected Gas-Phase Nitrogen-Oxygen Smiles Rearrangement: Collision-Induced Dissociation of Deprotonated 2-( N-Methylanilino)ethanol and Morpholinylbenzoic Acid Derivatives. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:2120-2128. [PMID: 36269933 PMCID: PMC10959088 DOI: 10.1021/jasms.2c00210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
A nitrogen-oxygen Smiles rearrangement was reported to occur after collisional activation of the PhN(R)CH2CH2O- (R = alkyl) anion, which undergoes a five-membered ring rearrangement to form a phenoxide ion C6H5O-. When R = H, such a Smiles rearrangement is unlikely since the negative charge is more favorably located on the nitrogen atom than the oxygen atom; hence, alternative neutral losses dominate the fragmentation. For example, collisional activation of deprotonated 2-anilinoethanol (PhN-CH2CH2OH) leads to the formation of an anilide anion (C6H5NH-, m/z 92) rather than a phenoxide ion (C6H5O-, m/z 93.0343). However, when the amino hydrogen of 2-anilinoethanol is substituted by a methyl group, i.e., 2-(N-methylanilino)ethanol, a Smiles rearrangement does occur, leading to the phenoxide ion, as the negative charge can only reside on the oxygen atom. To confirm the Smiles rearrangement mechanism, 2-(N-methylanilino)ethanol-18O was synthesized and subjected to collisional activation, leading to an intense peak at m/z 95.0385, which corresponds to the 18O phenoxide ion ([C6H518O]-). The abundance of the phenoxide ion is sensitive to substituents on the N atom, as demonstrated by the observation that an ethyl substituent results in the rearrangement ion with a much lower abundance. The nitrogen-oxygen Smiles rearrangement also occurs for various morpholinylbenzoic acid derivatives with a multistep mechanism, where the phenoxide ion is found to be predominantly formed after loss of CO2, proton transfers, breaking of the morpholine ring, and Smiles rearrangement. The Smiles mechanism is also supported by density functional theory calculations and other observations.
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Affiliation(s)
- Yuxue Liang
- Mass Spectrometry Data Center, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Yamil Simón-Manso
- Mass Spectrometry Data Center, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Pedatsur Neta
- Mass Spectrometry Data Center, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Stephen E Stein
- Mass Spectrometry Data Center, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
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Ding X, Kumar M, Zheng Z, Lee A, Hopkins WS, Attygalle AB. Evidence of Gas-Phase Attachment of Molecular Oxygen to Deprotonated Hydroquinone During Ion-Mobility Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:1816-1824. [PMID: 36129840 DOI: 10.1021/jasms.1c00222] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Gas-phase addition of dioxygen to certain ions is a well-known phenomenon in mass spectrometry. For this reaction to occur, the presence of a distonic radical site on the precursor ion is thought to be a prerequisite. Herein, we report that oxygen adduct formation can take place also with deprotonated hydroquinone, which in fact is an even-electron species without a radical site. When the product-ion spectrum of the m/z 109 ion, generated by electrospray ionization from a solution of hydroquinone in acetonitrile, was recorded under ion-mobility conditions, a new peak was observed at m/z 141. However, an analogous peak was not visible in the spectrum acquired under nonmobility conditions (i.e., without any gas introduced to the mobility cell). Presumably, traces of oxygen present in the collision gas instigate an ion-molecule reaction to produce an adduct of m/z 141, which upon activation results in CO and H2O loss to form a product ion of m/z 95. Isotope-labeling studies confirmed that one of the hydrogen atoms from the hydroxy group and another from the aromatic ring contribute to the water loss instigated from the m/z 141 adduct. Furthermore, computational methods indicated the three-dimensional structure of the ground-state deprotonated hydroquinone to be distinctly different from those of its 1,2- and 1,3-isomers. Calculations predicted that all atoms in the two m/z 109 ions generated from catechol and resorcinol lie on one plane. In contrast, the structure of the m/z 109 ion from hydroquinone was significantly different. Computations predicted that the hydrogen atom on the intact hydroxyl group of deprotonated hydroquinone protrudes out of plane from rest of the atoms. Consequently, the exposed OH group can interact with an incoming dioxygen molecule. Computations conducted at the CAM-B3LYP/6-311++g(2d,2p) level of theory detected a minimum energy crossing point (MECP) at -4.3 kJ mol-1 below the separated O2 + deprotonated hydroquinone triplet threshold. In contrast, similar calculations conducted for catechol and resorcinol yielded MECPs of +116.9 and +69.1 kJ mol-1, respectively, above the associated triplet thresholds. These results indicated that the curve crossing required to form singlet products upon reaction with triplet O2 is favorable in the case of hydroquinone and unfavorable in the cases of catechol and resorcinol. In practical terms, the selective oxygen addition appears to be a diagnostically useful reaction to differentiate hydroquinone from its ring isomers.
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Affiliation(s)
- Xiao Ding
- Center for Mass Spectrometry, Department of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
| | - Meenu Kumar
- Center for Mass Spectrometry, Department of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
| | - Zhaoyu Zheng
- Center for Mass Spectrometry, Department of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
| | - Arthur Lee
- Department of Chemistry and Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - W Scott Hopkins
- Department of Chemistry and Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Athula B Attygalle
- Center for Mass Spectrometry, Department of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Hoboken, New Jersey 07030, United States
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Direct Amination of Benzene with Molecular Nitrogen Enabled by Plasma‐Liquid Interactions. Angew Chem Int Ed Engl 2022; 61:e202203680. [DOI: 10.1002/anie.202203680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Indexed: 11/07/2022]
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Liu TT, Zhai DD, Guan BT, Shi ZJ. Nitrogen fixation and transformation with main group elements. Chem Soc Rev 2022; 51:3846-3861. [PMID: 35481498 DOI: 10.1039/d2cs00041e] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Nitrogen fixation is essential for the maintenance of life and development of society, however, the large bond dissociation energy and nonpolarity of the triple bond constitute a considerable challenge. The transition metals, by virtue of their combination of empty and occupied d orbitals, are prevalent in the nitrogen fixation studies and are continuing to receive a significant focus. The main group metals have always been considered incapable in dinitrogen activation owing to the absence of energetically and symmetrically accessible orbitals. The past decades have witnessed significant breakthroughs in the dinitrogen activation with the main group elements and compounds via either matrix isolation, theoretical calculations or synthetic chemistry. The successful reactions of the low-valent species of the main group elements with inert dinitrogen have been reported via the π back-donation from either the d orbitals (Ca, Sr, Ba) or p orbitals (Be, B, C…). Herein, the significant achievements have been briefly summarized, along with predicting the future developments.
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Affiliation(s)
- Tong-Tong Liu
- Department of Chemistry, Fudan University, 2005 Songhu Rd, Shanghai, 200438, China.
| | - Dan-Dan Zhai
- Department of Chemistry, Fudan University, 2005 Songhu Rd, Shanghai, 200438, China.
| | - Bing-Tao Guan
- Department of Chemistry, Fudan University, 2005 Songhu Rd, Shanghai, 200438, China.
| | - Zhang-Jie Shi
- Department of Chemistry, Fudan University, 2005 Songhu Rd, Shanghai, 200438, China.
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Xu X, Zhao X, Tang J, Duan Y, Tian Y. Direct Amination of Benzene with Molecular Nitrogen Enabled by Plasma‐Liquid Interactions. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202203680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Xia Xu
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education College of Chemistry and Materials Science Northwest University Xi'an Shaanxi 710027 China
| | - Xuyang Zhao
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education College of Chemistry and Materials Science Northwest University Xi'an Shaanxi 710027 China
| | - Jie Tang
- State Key Laboratory of Transient Optics and Photonics Xi'an Institute of Optics and Precision Mechanics of CAS Xi'an Shaanxi 710119 China
| | - Yixiang Duan
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education College of Chemistry and Materials Science Northwest University Xi'an Shaanxi 710027 China
| | - Yong‐Hui Tian
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education College of Chemistry and Materials Science Northwest University Xi'an Shaanxi 710027 China
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Chen Y, Huang L, Yuan X, Luo F, Pu H. Development and Validation of a UPLC-MS/MS Method for Ultra-Trace Level Determination of Acyl Chloride Potential Genotoxic Impurity in Mezlocillin. J Chromatogr Sci 2021; 60:732-740. [PMID: 34718453 DOI: 10.1093/chromsci/bmab119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 05/10/2021] [Indexed: 11/14/2022]
Abstract
3-Chlorocarbonyl-1-methanesulfonyl-2-imidazolidinone (CMI) is a critical intermediate used in the synthesis of mezlocillin drug substance and also a potential genotoxic impurity with acyl chloride moiety. The content of CMI in mezlocillin should be <0.16 ppm to avoid the carcinogenicity and mutagenicity threats to patients. Therefore, a workable determination of CMI was critically crucial for ensuring the safety of mezlocillin drug products. However, the conventional HPLC method is insufficient for detection limits at ppm or lower levels. Besides, the high activity of acyl chloride also raises a challenge to the direct measurement of CMI. Thus, we explored a simple esterification approach, which converts CMI into methyl 3-(methylonyl)-2-oxoimidazolidine-1-carboxylate completely by optimizing the reaction temperature and time. Furthermore, the selected reaction monitoring model of triple quadrupole mass spectrometer optimized by the Box-Behnken design significantly enhanced the sensitivity of ultra-trace level determination. The limit of detection and limit of quantification of the method were reached 0.014 and 0.02 ppm, respectively, in the following validation study. A sensitive and specific ultra-performance liquid chromatography tandem mass spectrometry method for ultra-trace level determination of acyl chloride potential genotoxic impurity in mezlocillin drug substance has been successfully established in this study, which will provide a practical quality control tool of mezlocillin.
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Affiliation(s)
- Yuanqiu Chen
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Lianzhou Huang
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Xiao Yuan
- Guangzhou PI & PI Biotech, Inc. Guangzhou 510663, China.,Wuhan Botanical Garden of Chinese Academy of Sciences, Wuhan 430074, China
| | - Feng Luo
- Guangzhou PI & PI Biotech, Inc. Guangzhou 510663, China
| | - Hanlin Pu
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
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Xu X, Dai J, Guo X, Qian C, Zhang P, Duan Y, Tian Y. Effective N 2 capture by aryl cations at ambient temperature and pressure. Phys Chem Chem Phys 2021; 23:10763-10767. [PMID: 33928338 DOI: 10.1039/d1cp00903f] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Here, we show that molecular N2 was efficiently captured by organic arylium cations in a well-defined manner at ambient pressure and temperature, which was monitored by on-line mass spectrometry analysis. A kinetic picture was proposed to disclose the principle of the ion-molecule reaction behavior for exclusive aryldiazonium production. The observation has an implication for direct nitrogen fixation into an organic framework via the intermediacy of such cationic species.
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Affiliation(s)
- Xia Xu
- Research Center of Analytical Instrumentation, Key Laboratory of Synthetic and Natural Functional Molecule of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710027, China.
| | - Jianxiong Dai
- Research Center of Analytical Instrumentation, Key Laboratory of Synthetic and Natural Functional Molecule of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710027, China.
| | - Xing Guo
- Research Center of Analytical Instrumentation, Key Laboratory of Synthetic and Natural Functional Molecule of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710027, China.
| | - Cheng Qian
- Research Center of Analytical Instrumentation, Key Laboratory of Synthetic and Natural Functional Molecule of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710027, China.
| | - Pei Zhang
- Research Center of Analytical Instrumentation, Key Laboratory of Synthetic and Natural Functional Molecule of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710027, China.
| | - Yixiang Duan
- Research Center of Analytical Instrumentation, Key Laboratory of Synthetic and Natural Functional Molecule of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710027, China.
| | - Yonghui Tian
- Research Center of Analytical Instrumentation, Key Laboratory of Synthetic and Natural Functional Molecule of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, Shaanxi 710027, China.
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9
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Chai Y, Chen H, Lu C. An intriguing "reversible reaction" in the fragmentation of deprotonated dicamba and benzoic acid in a Q-orbitrap mass spectrometer: Loss and addition of carbon dioxide. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2020; 34:e8893. [PMID: 32666557 DOI: 10.1002/rcm.8893] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 07/10/2020] [Accepted: 07/10/2020] [Indexed: 06/11/2023]
Abstract
RATIONALE Loss of carbon dioxide is an important characteristic fragmentation reaction of deprotonated benzoic acid and its derivatives in electrospray ionization mass spectrometry. However, researchers have rarely noticed or believed that the loss of carbon dioxide in multistage mass spectrometry is a "reversible reaction," that is, the fragment anion generated by carbon dioxide loss can capture another carbon dioxide to regenerate its precursor ion. METHODS The fragmentation of the [M - H]- ions of dicamba (3,6-dichloro-2-methoxybenzoic acid) and benzoic acid was performed with an electrospray ionization hybrid quadrupole-orbitrap mass spectrometer. The structural confirmation of the precursor ions and their product ions was supported by accurate mass (elemental composition) analysis. Pseudo-MS3 experiments (in-source collision-induced dissociation as MS2 ) and isotope labelling experiments were used to confirm the addition of carbon dioxide to the product ions in MS2 . RESULTS In the fragmentation of deprotonated dicamba (m/z 219), the relative abundance of the precursor ion does not decrease significantly or even increases as the collision energy increases. When the m/z 145 and 175 product ions were isolated in the mass analyzer, the ions 44 m/z units larger (m/z 189 and 219) were generated spontaneously, indicating the formation of carbon dioxide adduct ions. In the fragmentation of deprotonated [carboxyl-13 C]-benzoic acid (m/z 122), a deprotonated [carboxyl-12 C]-benzoic acid ion (m/z 121) was generated which was derived from 13 CO2 loss and 12 CO2 addition. The isotope labelling experiment further supports the formation of CO2 -attached ions in the fragmentation of deprotonated benzoic acids. CONCLUSIONS Under collisional activation, deprotonated dicamba and benzoic acids easily undergo carbon dioxide loss, but the decarboxylated product anions have an appropriate nucleophilicity to carbon dioxide and they can capture a background carbon dioxide molecule remaining in the vacuum system to regenerate the precursor ions. This study provides a new and deeper understanding of the gas-phase chemistry of deprotonated benzoic acid derivatives in mass spectrometry.
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Affiliation(s)
- Yunfeng Chai
- Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou, 310008, China
- Key Laboratory of Tea Quality and Safety Control, Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, China
- Laboratory of Quality and Safety Risk Assessment for Tea Products (Hangzhou), Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, China
| | - Hongping Chen
- Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou, 310008, China
- Key Laboratory of Tea Quality and Safety Control, Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, China
- Laboratory of Quality and Safety Risk Assessment for Tea Products (Hangzhou), Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, China
| | - Chengyin Lu
- Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou, 310008, China
- Key Laboratory of Tea Quality and Safety Control, Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, China
- Laboratory of Quality and Safety Risk Assessment for Tea Products (Hangzhou), Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, China
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Chai Y, Wang L, Lu C. Formation of molecular oxygen- and water-attached fragment ions in the fragmentation of protonated 3-(phenylthio)chromones. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2020; 34:e8567. [PMID: 31469930 DOI: 10.1002/rcm.8567] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 08/16/2019] [Accepted: 08/26/2019] [Indexed: 06/10/2023]
Affiliation(s)
- Yunfeng Chai
- Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou, 310008, P.R. China
- Key Laboratory of Tea Quality and Safety Control, Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, P.R. China
| | - Lu Wang
- University of Hawaii Cancer Center, 701 Ilalo Street, Room 254, Honolulu, HI, 96813, USA
| | - Chengyin Lu
- Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou, 310008, P.R. China
- Key Laboratory of Tea Quality and Safety Control, Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, P.R. China
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11
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Chai Y, Chen H, Liu X, Lu C. Formation of Carbon Dioxide Attached Fragment Ions in the Fragmentation of Deprotonated Tolfenpyrad and Tebufenpyrad. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:2060-2067. [PMID: 31338738 DOI: 10.1007/s13361-019-02273-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 06/19/2019] [Accepted: 06/19/2019] [Indexed: 06/10/2023]
Abstract
The in-source collision-induced dissociation (CID) and MS/MS mass spectra of deprotonated tolfenpyrad and tebufenpyrad both showed an unusual fragment ion at m/z 187, but its fragmentation pattern and structure could not be explained by logical neutral losses. Accurate mass measurement indicated that the mass difference between this fragment ion and the dominant fragment ion at m/z 143 equaled to a carbon dioxide (CO2) molecule. The isolation of the fragment ion m/z 143 in the mass analyzer could spontaneously give rise to the ion m/z 187. The Gibbs free energy of carbon dioxide addition to deprotonated pyrazole ion was significantly negative from the computational results. According to these results, we derived a proposal for the formation and structure of the ion m/z 187, which was an attachment of molecular carbon dioxide to the fragment ion m/z 143 to produce a carboxylate anion. The trace carbon dioxide was speculated to be derived from the residual atmosphere or collision gas in the instrument. This study is valuable for the qualitative and quantitative mass spectrometry analysis of pesticides containing the pyrazole functional group.
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Affiliation(s)
- Yunfeng Chai
- Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou, 310008, People's Republic of China
- Key Laboratory of Tea Quality and Safety Control, Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, People's Republic of China
- Laboratory of Quality and Safety Risk Assessment for Tea Products (Hangzhou), Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, People's Republic of China
| | - Hongping Chen
- Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou, 310008, People's Republic of China
- Key Laboratory of Tea Quality and Safety Control, Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, People's Republic of China
- Laboratory of Quality and Safety Risk Assessment for Tea Products (Hangzhou), Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, People's Republic of China
| | - Xin Liu
- Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou, 310008, People's Republic of China.
- Key Laboratory of Tea Quality and Safety Control, Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, People's Republic of China.
- Laboratory of Quality and Safety Risk Assessment for Tea Products (Hangzhou), Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, People's Republic of China.
| | - Chengyin Lu
- Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou, 310008, People's Republic of China.
- Key Laboratory of Tea Quality and Safety Control, Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, People's Republic of China.
- Laboratory of Quality and Safety Risk Assessment for Tea Products (Hangzhou), Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, 310008, People's Republic of China.
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Schorr P, Volmer DA. Using differential ion mobility spectrometry to perform class-specific ion-molecule reactions of 4-quinolones with selected chemical reagents. Anal Bioanal Chem 2019; 411:6247-6253. [PMID: 30972473 DOI: 10.1007/s00216-019-01789-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 03/12/2019] [Accepted: 03/18/2019] [Indexed: 11/26/2022]
Abstract
Gas phase ion/molecule reactions are often used in analytical applications to support the analysis of isomers or to identify specific functional groups of organic molecules. Until now, deliberate chemical reactions have not been performed in differential ion mobility spectrometry (DMS) devices except for hydrogen exchange and cluster formation. The present work extends that of Colorado and Brodbelt (Anal Chem 66:2330-5, 1994) on ion/molecule reactions in an ion trap mass spectrometer. In this study, class-specific chemical reactions of 4-quinolone antibiotics with various chemical reagents were used to demonstrate the analytical utility of ion/molecule reactions in a DMS drift cell. For these reactions, dehydrated reactive precursor ions were initially formed and made to undergo annulation reactions with selected reagents within the timescale of the DMS separation. Careful study of the energies required for dissociation of the adducts confirmed the covalent nature of the newly formed bond; thus demonstrating the analytical utility of this approach. Graphical abstract.
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Affiliation(s)
- Pascal Schorr
- Bioanalytical Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Germany
| | - Dietrich A Volmer
- Bioanalytical Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489, Berlin, Germany.
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Zheng Z, Pavlov J, Attygalle AB. Fortuitous Ion-Molecule Reaction Enables Enumeration of Metal-Hydrogen Bonds Present in Gaseous Ions. ACS OMEGA 2019; 4:3965-3972. [PMID: 31459605 PMCID: PMC6648366 DOI: 10.1021/acsomega.8b03341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 02/01/2019] [Indexed: 05/02/2023]
Abstract
Upon mass selection and ion activation under mass spectrometric conditions, gaseous formate adducts of many metal formates undergo decarboxylation and form product ions that bear metal-hydrogen bonds. Fortuitously, we noted that negative-ion spectra of several such formate adducts showed many peaks that could not be rationalized by the conventional fragmentation pathways attributed to the precursor ion. Subsequent experimentation proved that these enigmatic peaks are due to an ion-molecule reaction that takes place between traces of adventitious water vapor in the collision gas and the in situ formed product anions bearing metal-hydrogen bonds, generated by the fragmentation of the formate adducts. Results show that metal-hydrogen bonds of the group 2 elements are particularly susceptible to this reaction. For example, in the product-ion spectrum of [Sr(η2-O2CH)3]-, the peak at m/z 91 for SrH3 - was accompanied by three peaks at higher m/z ratios. These peaks, at m/z 107, 123, and 139, represented SrH2(OH)1 -, SrH1(OH)2 -, and Sr(OH)3 -, respectively. These satellite peaks, which were separated by 16 m/z units, were attributed to adducts formed due to the high affinity of gas-phase anions bearing metal-hydrogen bonds to water. Although undesired, these peaks are diagnostically useful to determine the number of metal-hydrogen bonds present in a precursor ion. Even though the peaks were less pronounced, analogous reactions were noted from the adducts of the group 1 elements as well. Moreover, Gibbs free energy values computed for the interaction of [H-Mg(η2-O2CH)2]- with water to form [HO-Mg(η2-OCOH)2]- and H2 indicated that this is an exergonic reaction.
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14
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Schwarz H, Asmis KR. Identification of Active Sites and Structural Characterization of Reactive Ionic Intermediates by Cryogenic Ion Trap Vibrational Spectroscopy. Chemistry 2019; 25:2112-2126. [PMID: 30623993 DOI: 10.1002/chem.201805836] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 01/07/2019] [Indexed: 01/02/2023]
Abstract
Cryogenic ion trap vibrational spectroscopy paired with quantum chemistry currently represents the most generally applicable approach for the structural investigation of gaseous cluster ions that are not amenable to direct absorption spectroscopy. Here, we give an overview of the most popular variants of infrared action spectroscopy and describe the advantages of using cryogenic ion traps in combination with messenger tagging and vibrational predissociation spectroscopy. We then highlight a few recent studies that apply this technique to identify highly reactive ionic intermediates and to characterize their reactive sites. We conclude by commenting on future challenges and potential developments in the field.
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Affiliation(s)
- Helmut Schwarz
- Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623, Berlin, Germany
| | - Knut R Asmis
- Wilhelm-Ostwald Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstr. 2, 04103, Leipzig, Germany
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15
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Kind T, Tsugawa H, Cajka T, Ma Y, Lai Z, Mehta SS, Wohlgemuth G, Barupal DK, Showalter MR, Arita M, Fiehn O. Identification of small molecules using accurate mass MS/MS search. MASS SPECTROMETRY REVIEWS 2018; 37:513-532. [PMID: 28436590 PMCID: PMC8106966 DOI: 10.1002/mas.21535] [Citation(s) in RCA: 249] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 03/17/2017] [Accepted: 03/18/2017] [Indexed: 05/03/2023]
Abstract
Tandem mass spectral library search (MS/MS) is the fastest way to correctly annotate MS/MS spectra from screening small molecules in fields such as environmental analysis, drug screening, lipid analysis, and metabolomics. The confidence in MS/MS-based annotation of chemical structures is impacted by instrumental settings and requirements, data acquisition modes including data-dependent and data-independent methods, library scoring algorithms, as well as post-curation steps. We critically discuss parameters that influence search results, such as mass accuracy, precursor ion isolation width, intensity thresholds, centroiding algorithms, and acquisition speed. A range of publicly and commercially available MS/MS databases such as NIST, MassBank, MoNA, LipidBlast, Wiley MSforID, and METLIN are surveyed. In addition, software tools including NIST MS Search, MS-DIAL, Mass Frontier, SmileMS, Mass++, and XCMS2 to perform fast MS/MS search are discussed. MS/MS scoring algorithms and challenges during compound annotation are reviewed. Advanced methods such as the in silico generation of tandem mass spectra using quantum chemistry and machine learning methods are covered. Community efforts for curation and sharing of tandem mass spectra that will allow for faster distribution of scientific discoveries are discussed.
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Affiliation(s)
- Tobias Kind
- Genome Center, Metabolomics, UC Davis, Davis, California
| | - Hiroshi Tsugawa
- RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, Japan
| | - Tomas Cajka
- Genome Center, Metabolomics, UC Davis, Davis, California
| | - Yan Ma
- National Institute of Biological Sciences, Beijing, People’s Republic of China
| | - Zijuan Lai
- Genome Center, Metabolomics, UC Davis, Davis, California
| | | | | | | | | | - Masanori Arita
- RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, Japan
| | - Oliver Fiehn
- Genome Center, Metabolomics, UC Davis, Davis, California
- Faculty of Sciences, Department of Biochemistry, King Abdulaziz University, Jeddah, Saudi Arabia
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16
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Liang Y, Neta P, Yang X, Stein SE. Collision-Induced Dissociation of Deprotonated Peptides. Relative Abundance of Side-Chain Neutral Losses, Residue-Specific Product Ions, and Comparison with Protonated Peptides. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:463-469. [PMID: 29143271 DOI: 10.1007/s13361-017-1842-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 10/27/2017] [Accepted: 10/31/2017] [Indexed: 06/07/2023]
Abstract
High-accuracy MS/MS spectra of deprotonated ions of 390 dipeptides and 137 peptides with three to six residues are studied. Many amino acid residues undergo neutral losses from their side chains. The most abundant is the loss of acetaldehyde from threonine. The abundance of losses from the side chains of other amino acids is estimated relative to that of threonine. While some amino acids lose the whole side chain, others lose only part of it, and some exhibit two or more different losses. Side-chain neutral losses are less abundant in the spectra of protonated peptides, being significant mainly for methionine and arginine. In addition to the neutral losses, many amino acid residues in deprotonated peptides produce specific negative ions after peptide bond cleavage. An expanded list of fragment ions from protonated peptides is also presented and compared with those of deprotonated peptides. Fragment ions are mostly different for these two cases. These lists of fragments are used to annotate peptide mass spectral libraries and to aid in the confirmation of specific amino acids in peptides. Graphical Abstract ᅟ.
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Affiliation(s)
- Yuxue Liang
- Mass Spectrometry Data Center, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
| | - Pedatsur Neta
- Mass Spectrometry Data Center, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Xiaoyu Yang
- Mass Spectrometry Data Center, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Stephen E Stein
- Mass Spectrometry Data Center, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
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17
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Rohdenburg M, Mayer M, Grellmann M, Jenne C, Borrmann T, Kleemiss F, Azov VA, Asmis KR, Grabowsky S, Warneke J. Superelectrophilic Behavior of an Anion Demonstrated by the Spontaneous Binding of Noble Gases to [B 12 Cl 11 ]<sup/>. Angew Chem Int Ed Engl 2017; 56:7980-7985. [PMID: 28560843 DOI: 10.1002/anie.201702237] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Indexed: 11/06/2022]
Abstract
It is common and chemically intuitive to assign cations electrophilic and anions nucleophilic reactivity, respectively. Herein, we demonstrate a striking violation of this concept: The anion [B12 Cl11 ]- spontaneously binds to the noble gases (Ngs) xenon and krypton at room temperature in a reaction that is typical of "superelectrophilic" dications. [B12 Cl11 Ng]- adducts, with Ng binding energies of 80 to 100 kJ mol-1 , contain B-Ng bonds with a substantial degree of covalent interaction. The electrophilic nature of the [B12 Cl11 ]- anion is confirmed spectroscopically by the observation of a blue shift of the CO stretching mode in the IR spectrum of [B12 Cl11 CO]- and theoretically by investigation of its electronic structure. The orientation of the electric field at the reactive site of [B12 Cl11 ]- results in an energy barrier for the approach of polar molecules and facilitates the formation of Ng adducts that are not detected with reactive cations such as [C6 H5 ]+ . This introduces the new chemical concept of "dipole-discriminating electrophilic anions."
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Affiliation(s)
- Markus Rohdenburg
- Universität Bremen, Institut für Angewandte und Physikalische Chemie, Fachbereich 2-Biologie/Chemie, Leobener Str. NW2, 28359, Bremen, Germany
| | - Martin Mayer
- Universität Leipzig, Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Linnéstr. 2, 04103, Leipzig, Germany
| | - Max Grellmann
- Universität Leipzig, Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Linnéstr. 2, 04103, Leipzig, Germany
| | - Carsten Jenne
- Bergische Universität Wuppertal, Anorganische Chemie, Fakultät für Mathematik und Naturwissenschaften, Gaußstr. 20, 42119, Wuppertal, Germany
| | - Tobias Borrmann
- Universität Bremen, Institut für Angewandte und Physikalische Chemie, Fachbereich 2-Biologie/Chemie, Leobener Str. NW2, 28359, Bremen, Germany
| | - Florian Kleemiss
- Universität Bremen, Institut für Anorganische Chemie und Kristallographie, Fachbereich 2-Biologie/Chemie, Leobener Str. NW2, 28359, Bremen, Germany
| | - Vladimir A Azov
- Universität Bremen, Institut für Angewandte und Physikalische Chemie, Fachbereich 2-Biologie/Chemie, Leobener Str. NW2, 28359, Bremen, Germany.,N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky prospect 47, Moscow, 119991, Russia
| | - Knut R Asmis
- Universität Leipzig, Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Linnéstr. 2, 04103, Leipzig, Germany
| | - Simon Grabowsky
- Universität Bremen, Institut für Anorganische Chemie und Kristallographie, Fachbereich 2-Biologie/Chemie, Leobener Str. NW2, 28359, Bremen, Germany
| | - Jonas Warneke
- Pacific Northwest National Laboratory, Physical Science Division, Richland, WA, 99352, USA
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18
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Rohdenburg M, Mayer M, Grellmann M, Jenne C, Borrmann T, Kleemiss F, Azov VA, Asmis KR, Grabowsky S, Warneke J. Superelektrophiles Verhalten eines Anions demonstriert durch spontane Bindung von Edelgasen an [B12
Cl11
]−. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201702237] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Markus Rohdenburg
- Universität Bremen; Institut für Angewandte und Physikalische Chemie; Fachbereich 2 - Biologie/Chemie; Leobener Str. NW2 28359 Bremen Deutschland
| | - Martin Mayer
- Universität Leipzig; Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie; Linnéstr. 2 04103 Leipzig Deutschland
| | - Max Grellmann
- Universität Leipzig; Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie; Linnéstr. 2 04103 Leipzig Deutschland
| | - Carsten Jenne
- Bergische Universität Wuppertal; Anorganische Chemie; Fakultät für Mathematik und Naturwissenschaften; Gaußstr. 20 42119 Wuppertal Deutschland
| | - Tobias Borrmann
- Universität Bremen; Institut für Angewandte und Physikalische Chemie; Fachbereich 2 - Biologie/Chemie; Leobener Str. NW2 28359 Bremen Deutschland
| | - Florian Kleemiss
- Universität Bremen; Institut für Anorganische Chemie und Kristallographie; Fachbereich 2 - Biologie/Chemie; Leobener Str. NW2 28359 Bremen Deutschland
| | - Vladimir A. Azov
- Universität Bremen; Institut für Angewandte und Physikalische Chemie; Fachbereich 2 - Biologie/Chemie; Leobener Str. NW2 28359 Bremen Deutschland
- N. D. Zelinsky Institut für Organische Chemie; Russische Akademie der Wissenschaften; Leninsky prospect 47 Moskau 119991 Russland
| | - Knut R. Asmis
- Universität Leipzig; Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie; Linnéstr. 2 04103 Leipzig Deutschland
| | - Simon Grabowsky
- Universität Bremen; Institut für Anorganische Chemie und Kristallographie; Fachbereich 2 - Biologie/Chemie; Leobener Str. NW2 28359 Bremen Deutschland
| | - Jonas Warneke
- Pacific Northwest National Laboratory; Physical Science Division; Richland WA 99352 USA
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Telu KH, Yan X, Wallace WE, Stein SE, Simón-Manso Y. Analysis of human plasma metabolites across different liquid chromatography/mass spectrometry platforms: Cross-platform transferable chemical signatures. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30:581-93. [PMID: 26842580 PMCID: PMC5114847 DOI: 10.1002/rcm.7475] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
RATIONALE The metabolite profiling of a NIST plasma Standard Reference Material (SRM 1950) on different liquid chromatography/mass spectrometry (LC/MS) platforms showed significant differences. Although these findings suggest caution when interpreting metabolomics results, the degree of overlap of both profiles allowed us to use tandem mass spectral libraries of recurrent spectra to evaluate to what extent these results are transferable across platforms and to develop cross-platform chemical signatures. METHODS Non-targeted global metabolite profiles of SRM 1950 were obtained on different LC/MS platforms using reversed-phase chromatography and different chromatographic scales (conventional HPLC, UHPLC and nanoLC). The data processing and the metabolite differential analysis were carried out using publically available (XCMS), proprietary (Mass Profiler Professional) and in-house software (NIST pipeline). RESULTS Repeatability and intermediate precision showed that the non-targeted SRM 1950 profiling was highly reproducible when working on the same platform (relative standard deviation (RSD) <2%); however, substantial differences were found in the LC/MS patterns originating on different platforms or even using different chromatographic scales (conventional HPLC, UHPLC and nanoLC) on the same platform. A substantial degree of overlap (common molecular features) was also found. A procedure to generate consistent chemical signatures using tandem mass spectral libraries of recurrent spectra is proposed. CONLUSIONS Different platforms rendered significantly different metabolite profiles, but the results were highly reproducible when working within one platform. Tandem mass spectral libraries of recurrent spectra are proposed to evaluate the degree of transferability of chemical signatures generated on different platforms. Chemical signatures based on our procedure are most likely cross-platform transferable.
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Affiliation(s)
| | | | | | | | - Yamil Simón-Manso
- Address reprint requests to: Yamil Simón-Manso, Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA, Telephone: 301-975-8638, Fax: 301-975-2643,
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20
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Ion-molecule adduct formation in tandem mass spectrometry. Anal Bioanal Chem 2015; 408:1269-77. [PMID: 26700446 DOI: 10.1007/s00216-015-9237-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 11/24/2015] [Accepted: 11/30/2015] [Indexed: 10/22/2022]
Abstract
Nowadays most LC-MS methods rely on tandem mass spectrometry not only for quantitation and confirmation of compounds by multiple reaction monitoring (MRM), but also for the identification of unknowns from their product ion spectra. However, gas-phase reactions between charged and neutral species inside the mass analyzer can occur, yielding product ions at m/z values higher than that of the precursor ion, or at m/z values difficult to explain by logical losses, which complicate mass spectral interpretation. In this work, the formation of adduct ions in the mass analyzer was studied using several mass spectrometers with different mass analyzers (ion trap, triple quadrupole, and quadrupole-Orbitrap). Heterocyclic amines (AαC, MeAαC, Trp-P-1, and Trp-P-2), photo-initiators (BP and THBP), and pharmaceuticals (phenacetin and levamisole) were selected as model compounds and infused in LCQ Classic, TSQ Quantum Ultra AM, and Q-Exactive Orbitrap (ThermoFisher Scientific) mass spectrometers using electrospray as ionization method. The generation of ion-molecule adducts depended on the compound and also on the instrument employed. Adducts with neutral organic solvents (methanol and acetonitrile) were only observed in the ion trap instrument (LCQ Classic), because of the ionization source on-axis configuration and the lack of gas-phase barriers, which allowed inertial entrance of the neutrals into the analyzer. Adduct formation (only with water) in the triple quadrupole instruments was less abundant than in the ion trap and quadrupole-Orbitrap mass spectrometers, because of the lower residence time of the reactive product ions in the mass analyzer. The moisture level of the CID and/or damper gas had a great effect in beam-like mass analyzers such as triple quadrupole, but not in trap-like mass analyzers, probably because of the long residence time that allowed adduct formation even with very low concentrations of water inside the mass spectrometer.
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