共查询到20条相似文献,搜索用时 31 毫秒
1.
Changfu Cheng Daryl Giblin Michael L. Gross 《Journal of the American Society for Mass Spectrometry》1998,9(3):216-224
A strategy is described to locate the carbonyl position in oxofatty acids by utilizing charge-remote fragmentations of various molecular ions that are desorbed by fast atom bombardment (FAB). Oxofatty acids were cationized with alkali metal ions (Li+, Na+, K+, Rb+, and Cs+) to form [M+2Met?H]+ or alkaline earth metal ions (Mg2+, Ca2+, Sr2+ or Ba2+) to form [M+Met?H]+ in the gas phase. The cationized acids undergo charge-remote fragmentations upon high-energy activation, giving a product-ion pattern that has a gap corresponding to the oxo position and bordered by two high-intensity peaks. One of the peaks corresponds to an ion that is formed by the cleavage of the C-C bond β to the oxo position and proximal to the charge (β ion), whereas the other is formed from the cleavage of the C-C bond γ to the oxo position and distal to the charge (γ′ ion). The oxo position is easily determined by identifying the gap and the β and γ′ ions. Furthermore, there are two competing patterns of fragments in a CAD spectrum of an oxofatty acid or ester [M+Li]+ ion. These arise because Li+ attaches to either the oxo or the carboxylic end, as was confirmed by ab initio molecular orbital calculations. The results demonstrate that control of the fragmentation can be guided by an understanding of metal-ion affinities. Collisional activation of the anionic carboxylates gives results that are similar to those for positive ions, showing that the process is not related to the charge status. Collisional activation of [M+H]+ ions does not give structural information because the charge migrates, leading to charge-mediated fragmentations. 相似文献
2.
Dami Barcel 《Journal of mass spectrometry : JMS》1989,24(10):898-902
The effect of two completely different mobile phase compositions, reversed-phase acetonitrile-water + ammonium acetate and normal-phase cyclohexane, were compared in filament-on thermospray liquid chromatography-mass spectrometry (LC-MS) for the determination of selected chlorinated herbicides such as chloroatrazines and chlorinated phenoxyacetic acids. By using acetonitrile-water + 0.05 M ammonium acetate mixtures in positive ion mode thermospray LC-MS, the chloroatrazine herbicides showed the acetonitrile adduct ion [M + (CH3CN)H]+ as the base peak, whereas the chlorinated phenoxyacetic acids showed no signal. In contrast, when cyclohexane, which is reported for the first time as an eluent in the thermospray technique, was used as the mobile phase the chlorinated phenoxyacetic acid herbicides exhibited [M – H]+, [M – Cl]+ and M+˙ as the main ions. Negative ion mode thermospray LC-MS showed [M – H]? as the base peak for the chloroatrazines in the different mobile phases, whereas the chlorinated phenoxyacetic acids exhibited [M + H]?, [M + Cl]? or [M – HCl]? as the base peaks in cyclohexane and [M + acetate]? in acetonitrile-water-ammonium acetate. 相似文献
3.
Yo Ueda K
ichi Mori Keiki Kouno Tokihiro Nhya 《Journal of mass spectrometry : JMS》1976,11(10):1027-1036
The mass spectra of 30 sulfinamide derivatives (RSONHR', R' alkyl or p-XC6H4) are reported. Most of the spectra had peaks attributable to thermal decomposition products. For some compounds these were identified by pyrolysis under similar conditions to be: RSO2NHR', RSO2SR, RSSR and NH2R' (in all kinds of sulfinyl amides); RSNHR' (in the case of arylsulfinyl arylamides); RSO2C6H4NH2, RSOC6H4NH2 and RSC6H4NH2 (in the case of arylsulfinyl arylamides of the type of X = H) The mass spectra of the three thermally stable compounds showed that there are several kinds of common fragment ions. The mass spectra of the thermally labile compounds had two groups of ions; (i) characteristic fragment ions of the intact molecules and (ii) the molecular ions of the thermal decomposition products. It was concluded that the sulfinamides give the following ions after electron impact: [M]+, [M ? R]+, [M ? R + H]+, [M ? SO]+, [RS]+, [NHR']+, [NHR' + H]+, [RSO]+, [RSO + H]+, [R]+, [R + H]+, [R']+ and [M ? OH]+, and that the thermal decomposition products give the following ions: [RSO2SR]+, [RSSR]+, [M ? O]+, [M + O]+ and [RSOC6H4NH2]+. 相似文献
4.
J. W. Dallinga N. M. M. Nibbering J. Van Der Greef M. C. Ten Noever De Brauw 《Journal of mass spectrometry : JMS》1984,19(1):10-15
Geometrically isomeric dicarboxylic acids, such as maleic and fumaric acid and their methyl homologues, and the isomeric phthalic acids, have been investigated using fast atom bombardment, field ionization and field desorption mass spectrometry. The most intense peak in the positive ion fast atom bombardment spectra corresponds with the [M + H]+ ion. This ion, when derived from the E -acids, tragments either by successive loss of water and carbon monoxide or by elimination of carbon dioxide. In the case of the Z -acids only elimination of water from the [M + H]+ ions is observed to occur to a significant extent. The same is true for the [M + H]+ ions of the isomeric phthalic acids, that is the [M + H] ions derived from iso- and terephthalic acid exhibit more fragmentation than those of phthalic acid. All these acids undergo much less fragmentation upon field ionization, where not only abundant [M + H]+ ions, but also abundant [M]+· ions, are observed. Upon field desorption only the [M + H]+ and [M + Na]+ ions are observed under the measuring conditions. Negative ion fast atom bombardment spectra of the acids mentioned have also been recorded. In addition to the most abundant [M? H]? ions relatively intense peaks are observed, which correspond with the [M]?˙ ions. The fragmentations observed for these ions appear to be quite different from those reported in an earlier electron impact study and in a recent atmospheric pressure ionization investigation. 相似文献
5.
The fragmentations of [(CH3)2SiO]n, (Dn), where n = 4, 5, 6, 7, 8, 9, 10, 12 and 15 are reported. The behaviour of these compounds under electron-impact is governed by the size of the siloxane ring. Rings smaller than D6 have base peaks corresponding to [M – 15]+ ions; larger rings all show base peaks of m/e 73 [Si(CH3)3]+. A transannular mechanism previously applied only to D5 and D6 is extended and modified to account for the behaviour of larger rings. A ring con-traction mechanism is proposed which leads to the formation of smaller rings and doubly charged ions. A new transannular mechanism is proposed to account for the production of [M – 177]+ and [M – 193]+ ions. 相似文献
6.
The mass spectra of twenty-nine sydnones were measured by using NII3 as a reagent gas. The [M + H + NH3]+ ions are the base peaks for the entire series. Very few fragment ions were observed except for the derivatives of 4-hydroxymethylenesydnones (XXI-XXIX). Only the relatively stable sydnonyl-methylene cations are formed. With consistent formation of [M + 18]+ ion as the base peaks with simple spectra, the NH3 CI-MS can be an excellent method for the molecular weight determination. 相似文献
7.
Nitric oxide chemical ionization mass spectra of substituted benzenes obtained with the Townsend discharge technique were studied. There were four kinds of base peaks in the mass spectra, i.e. [M + NO]+˙, M+˙, [M ? H]+ and [M ? OR]+ (R = H, CH3). The formation of the specific ion [M + NO]+˙ was highly dependent on the kind of substituent, and it was produced more abundantly in the case of substitutions involving electron-accepting groups. The measure of [M + NO]+˙ production was evaluated from the value of the ratio [M + NO]+˙/M+˙. In mono-substitutions, it was clarified that the ratios of [M + NO]+˙/M +˙ were correlated with the Hammett substituent constant s?p or the electrophilic substituent constant s?p+. Monosubstitutions (C6H5R) and toluene substitutions (CH3C6H4R) could be classified into six groups in terms of base peak species, [M + NO]+˙/M+˙ ratios and substituents. In disubstitutions, the mass spectral patterns were governed by the combination of substituents. Mass spectral distinctions among ortho, meta and para isomers could be made in many cases. 相似文献
8.
Ilpo O. O. Korhonen 《Journal of mass spectrometry : JMS》1982,17(11):553-557
The mass spectral fragmentations of methyl mono- and dichlorobutanates have been studied. Deutrium labelling and metastable ion analysis were used to elucidate the fragmentation mechanisms. The molecular ion peaks of the esters are weak and show only in the spectra of the monochloro isomers. A McLafferty rearrangement gives the base peaks in the spectra of methyl 2-chloro-, 4-chloro- and 4,4-dichlorobutanoate; α-cleavage, [COOCH3]+, in methyl 2,2- and 2,4-dichlorobutanoate; [M? Cl]+, in methyl 3-chlorobutanoate; [M? Cl? HCl]+, in methyl 3,4-dichlorobutanoate; [M? Cl? CH2CO]+, in methyl 3,3-dichlorobutanoate and [M? Cl? COOCH3]+˙, in methyl erythro- and threo-2,3-dichlorobutanoate. The mass spectra of the stereoisomers are nearly identical, the loss of a chlorine atom and the McLafferty rearrangement giving the higher peaks in the spectrum of the threo form. 相似文献
9.
Motoshi Sakakura Mitsuo Takayama 《Journal of the American Society for Mass Spectrometry》2010,21(6):979-988
The use of 5-aminosalicylic acid (5-ASA) as a new matrix for in-source decay (ISD) of peptides including mono- and di-phosphorylated
peptides in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is described. The use of 5-ASA in MALDI-ISD
has been evaluated from several standpoints: hydrogen-donating ability, the outstanding sharpness of molecular and fragment
ion peaks, and the presence of interference peaks such as metastable peaks and multiply charged ions. The hydrogen-donating
ability of several matrices such as α-cyano-4-hydroxycinnamic acid (CHCA), 2,5-dihydroxybenzoic acid (2,5-DHB), 1,5-diaminonaphthalene
(1,5-DAN), sinapinic acid (SA), and 5-ASA was evaluated by using the peak abundance of a reduction product [M + 2H + H]+ to that of non-reduced protonated molecule [M + H]+ of the cyclic peptide vasopressin which contains a disulfide bond (S-S). The order of hydrogendonating ability was 1,5-DAN
> 5-ASA > 2,5-DHB > SA = CHCA. The chemicals 1,5-DAN and 5-ASA in particular can be classified as reductive matrices. 5-ASA
gave peaks with higher sharpness for protonated molecules and fragment ions than other matrices and did not give any interference
peaks such as multiply-protonated ions and metastable ions in the ISD mass spectra of the peptides used. Particularly, 1,5-DAN
and 5-ASA gave very little metastable peaks. This indicates that 1,5-DAN and 5-ASA are more “cool” than other matrices. The
1,5-DAN and 5-ASA can therefore be termed “reductive cool” matrix. Further, it was confirmed that ISD phenomena such as N-Cα
bond cleavage and reduction of S-S bond is a single event in the ion source. The characteristic fragmentations, which form
a− and (a + 2)-series ions, [M + H − 15]+, [M + H − 28]+, and [M + H − 44]+ ions in the MALDI-ISD are described. 相似文献
10.
Ken-Ichi Harada Katsuyoshi Masuda Makoto Suzuki Hisao Oka Yoshitomo Ikai Junko Hayakawa 《Journal of mass spectrometry : JMS》1993,28(12):1512-1515
In the fast atom bombardment mass spectra of tetracyclines, ammonia elimination fragment ions, [M + H – NH3]+ and [M + H – NH3 – H2O]+, appeared with considerable abundances. A plausible mechanism for the loss of ammonia from [M + H]+ was discussed based on results by measurements on various types of tetracyclines and benzamides as the model compounds and B/E linked scanning. The results indicated that the loss of ammonia occurred in the carboxyamide moiety in the A ring and was accelerated by an ortho-hydroxy group. The same fragmentations were observed in the electrospray mass spectra of tetracyclines with a skimmer-capillary voltage differential of 150 V. 相似文献
11.
在作黄酮和黄酮甙的快原子轰击质谱时,如果同时加入氯化钠和氯化钾两种碱金属盐,就会在谱图中同时出现两个强峰,由于这两个峰相差16个原子质量单位,很容量辨认,并且发现在其谱图中找不到明显的碎片离子和Na^+和K^+的加合离子,而只有其分子和K^+和Na^+的加合,所以很容易在FAB谱中识别它们,因而就可以快速,准确地确定样品的分子量。 相似文献
12.
Ilpo O. O. Korhonen 《Journal of mass spectrometry : JMS》1982,17(10):461-464
The mass spectral fragmentations of all eleven chlorinated methyl propanoates have been studied. Deuterium labelling and metastable ion analysis were used to elucidate the fragmentation mechanism. The molecular ion peaks of all compounds are small, except methyl 3,3-dichloropanoate (38%). In most cases α-cleavage gives the base peak [COOCH3]+, and the loss of a chlorine atom from the molecular ion is characteristic of the 3-chloro, 3,3-dichloro and 3,3,3-trichloro compounds. Metastable ions showed the losses of small neutral molecules such as CH3OH, CH2CO, CO2 and CO from the [M? Cl]+ ion. α-Cleavage and the loss of Cl˙ gives an intense [M? COOCH3? Cl]+˙ peak, which is the base peak in the spectra of the 2,3-dichloro and 2,3,3-trichloro compounds. 相似文献
13.
The fragmentations under electron impact of 5-phenyl-1,4-benzodiazepin-2-ones are investigated with the aid of high resolution, metastable decompositions and deuterium labeling. Based on our data a mechanism for the formation of the [M – H]+ ion is proposed. It is shown that the [M – CHO]+ ion is probably formed by two different pathways. Data on two minor fragment ions give support to the structure proposed for the [M – CHO]+ ion. 相似文献
14.
Low-energy CAD product-ion spectra of various molecular species of phosphatidylserine (PS) in the forms of [M−H]− and [M−2H+Alk]− in the negative-ion mode, as well as in the forms of [M+H]+, [M+Alk]+, [M−H+2Alk]+, and [M−2H+3Alk]+ (where Alk=Li, Na) in the positive-ion mode contain rich fragment ions that are applicable for structural determination.
Following CAD, the [M−H]− ion of PS undergoes dissociation to eliminate the serine moiety (loss of C3H5NO2) to give a [M−H−87]− ion, which equals to the [M−H]− ion of a phoshatidic acid (PA) and give rise to a MS3-spectrum that is identical to the MS2-spectrum of PA. The major fragmentation process for the [M−2H+Alk]− ion of PS arises from primary loss of 87 to give rise to a [M−2H+Alk−87]− ion, followed by loss of fatty acid substituents as acids (RxCO2H, x=1,2) or as alkali salts (e. g., RxCO2Li, x=1,2). These fragmentations result in a greater abundance of [M−2H+Alk−87−R2CO2H]− than [M−2H+Alk−87−R1CO2H]− and a greater abundance of [M−2H+Alk−87−R2CO2Li]− than [M−2H+Alk−87−R1CO2Li]−; while further dissociation of the [M−2H+Alk−87−R2(or 1)CO2Li]− ions gives a preferential formation of the carboxylate anion at sn-1 (R1CO2−) over that at sn-2 (R2CO2−). Other major fragmentation process arises from differential loss of the fatty acid substituents as ketenes (loss of Rx′CH=CO, x=1,2). This results in a more prominent [M−2H+Alk−R2′CH=CO]− ion than [M−2H+Alk−R1′CH=CO]− ion. Ions informative for structural characterization of PS are of low abundance in the MS2-spectra of both the [M+H]+ and the [M+Alk]+ ions, but are abundant in the MS3-spectra. The MS2-spectrum of the [M+Alk]+ ion contains a unique ion corresponding to internal loss of a phosphate group probably via the fragmentation processes involving
rearrangement steps. The [M−H+2Alk]+ ion of PS yields a major [M−H+2Alk−87]+ ion, which is equivalent to an alkali adduct ion of a monoalkali salt of PA and gives rise to a greater abundance of [M−H+2Alk−87−R1CO2H]+ than [M−H+2Alk−87−R2CO2H]+. Similarly, the [M−2H+3Alk]+ ion of PS also yields a prominent [M−2H+3Alk−87]+ ion, which undergoes consecutive dissociation processes that involve differential losses of the two fatty acyl substituents.
Because all of the above tandem mass spectra contain several sets of ion pairs involving differential losses of the fatty
acid substituents as ketenes or as free fatty acids, the identities of the fatty acyl substituents and their positions on
the glycerol backbone can be easily assigned by the drastic differences in the abundances of the ions in each pair. 相似文献
15.
Mass spectrometric monitoring of oxidation of aliphatic C6–C8 hydrocarbons and ethanol in low pressure oxygen and air plasmas
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Dilshadbek T. Usmanov Lee Chuin Chen Kenzo Hiraoka Hiroshi Wada Hiroshi Nonami Shinichi Yamabe 《Journal of mass spectrometry : JMS》2016,51(12):1187-1195
Experimental and theoretical studies on the oxidation of saturated hydrocarbons (n‐hexane, cyclohexane, n‐heptane, n‐octane and isooctane) and ethanol in 28 Torr O2 or air plasma generated by a hollow cathode discharge ion source were made. Ions corresponding to [M + 15]+ and [M + 13]+ in addition to [M ? H]+ and [M ? 3H]+ were detected as major ions where M is the sample molecule. The ions [M + 15]+ and [M + 13]+ were assigned as oxidation products, [M ? H + O]+ and [M ? 3H + O]+, respectively. By the tandem mass spectrometry analysis of [M ? H + O]+ and [M ? 3H + O]+, H2O, olefins (and/or cycloalkanes) and oxygen‐containing compounds were eliminated from these ions. Ozone as one of the terminal products in the O2 plasma was postulated as the oxidizing reagent. As an example, the reactions of C6H14+? with O2 and of C6H13+ (CH3CH2CH+CH2CH2CH3) with ozone were examined by density functional theory calculations. Nucleophilic interaction of ozone with C6H13+ leads to the formation of protonated ketone, CH3CH2C(=OH+)CH2CH2CH3. In air plasma, [M ? H + O]+ became predominant over carbocations, [M ? H]+ and [M ? 3H]+. For ethanol, the protonated acetic acid CH3C(OH)2+ (m/z 61.03) was formed as the oxidation product. The peaks at m/z 75.04 and 75.08 are assigned as protonated ethyl formate and protonated diethyl ether, respectively, and that at m/z 89.06 as protonated ethyl acetate. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
16.
Seymour Meyerson 《Journal of mass spectrometry : JMS》1970,3(1):119-125
Mass spectra of isotope-labeled triptycenes, triphenylmethanes and diphenylmethanes rule out the bulk of postulated decomposition mechanisms and fragment-ion structures. The formation of [M ? H]+ and [M ? 2H]2+ from triptycene, of [M ? H]+, [M ? CH3]+ and [M ? CH4]+ from triphenylmethane, and of [M ? H]2+ and [M ? 2H]2+-as well as the previously reported [M ? H]+ and [M ? CH3]+-from diphenylmethane all seem to be preceded or accompanied by complete loss of position identity of the α and ring hydrogens in the original molecules. A statistical preference for loss of α hydrogens is found in the process leading to [M ? 2H]+ and [M ? H]2+ from triptycene, as in the formation of [M ? H]2+ from toluene. 相似文献
17.
Estimation of peptide N–Cα bond cleavage efficiency during MALDI‐ISD using a cyclic peptide
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Daiki Asakawa Nicolas Smargiasso Edwin De Pauw 《Journal of mass spectrometry : JMS》2016,51(5):323-327
Matrix‐assisted laser desorption/ionization in‐source decay (MALDI‐ISD) induces N–Cα bond cleavage via hydrogen transfer from the matrix to the peptide backbone, which produces a c′/z? fragment pair. Subsequently, the z? generates z′ and [z + matrix] fragments via further radical reactions because of the low stability of the z?. In the present study, we investigated MALDI‐ISD of a cyclic peptide. The N–Cα bond cleavage in the cyclic peptide by MALDI‐ISD produced the hydrogen‐abundant peptide radical [M + 2H]+? with a radical site on the α‐carbon atom, which then reacted with the matrix to give [M + 3H]+ and [M + H + matrix]+. For 1,5‐diaminonaphthalene (1,5‐DAN) adducts with z fragments, post‐source decay of [M + H + 1,5‐DAN]+ generated from the cyclic peptide showed predominant loss of an amino acid with 1,5‐DAN. Additionally, MALDI‐ISD with Fourier transform‐ion cyclotron resonance mass spectrometry allowed for the detection of both [M + 3H]+ and [M + H]+ with two 13C atoms. These results strongly suggested that [M + 3H]+ and [M + H + 1,5‐DAN]+ were formed by N–Cα bond cleavage with further radical reactions. As a consequence, the cleavage efficiency of the N–Cα bond during MALDI‐ISD could be estimated by the ratio of the intensity of [M + H]+ and [M + 3H]+ in the Fourier transform‐ion cyclotron resonance spectrum. Because the reduction efficiency of a matrix for the cyclic peptide cyclo(Arg‐Gly‐Asp‐D‐Phe‐Val) was correlated to its tendency to cleave the N–Cα bond in linear peptides, the present method could allow the evaluation of the efficiency of N–Cα bond cleavage for MALDI matrix development. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
18.
Chemical ionization mass spectra of several ethers obtained with He/(CH3)4Si mixtures as the reagent gases contain abundant [M + 73]+ adduct ions which identify the relative molecular mass. For the di-n-alkyl ethers, these [M + 73]+ ions are formed by sample ion/sample molecule reactions of the fragment ions, [M + 73 ? CnH2n]+ and [M + 73 ? 2CnH2n]+. Small amounts of [M + H]+ ions are also formed, predominantly by proton transfer reactions of the [M + 73 ? 2CnH2n]+ or [(CH3)3SiOH2]+ ions with the ethers. The di-s-alkyl ethers give no [M + 73] + ions, but do give [M + H]+ ions, which allow the determination of the relative molecular mass. These [M + H]+ ions result primarily from proton transfer reactions from the dominant fragment ion, [(CH3)3SiOH2]+ with the ether. Methyl phenyl ether gives only [M + 73]+ adduct ions, by a bimolecular addition of the trimethylsilyl ion to the ether, not by the two-step process found for the di-n-alkyl ethers. Ethyl phenyl ether gives [M + 73]+ by both the two-step process and the bimolecular addition. Although the mass spectra of the alkyl etherr are temperature-dependent, the sensitivities of the di-alkyl ethers and ethyl phenyl ether are independent of temperature. However, the sensitivity for methyl phenyl ether decreases significantly with increasing temperature. 相似文献
19.
Vladimír Kov
ik Jn Hirsch W. Heerma C. G. de Koster J. Haverkamp 《Journal of mass spectrometry : JMS》1994,29(12):707-712
The positive-ion fast atom bombardment mass spectra of permethylated aldo- and pseudoaldobiouronic acids can be used to distinguish these classes of compounds. The collisional-induced dissociation spectra of the [M + H]+ ions show fragment ions resulting from glycosidic bond cleavage and successive losses of methanol molecules. These spectra together with those of the [M + H ? MeOH]+ oxonium ions allow the identification of the type of interglycosidic linkage. Collisional activation of the relatively stable [M + Na]+ ions show many fragmentations which are common to alkali cationized permethylated saccharides. Moreover, fragment ions resulting from two-bond ring cleavage processes yield additional information with respect to the linkage between the hexose and uronic acid units. 相似文献
20.
Burnaby Munson Ta-Min Feng Harry D. Ward Roger K. Murray 《Journal of mass spectrometry : JMS》1987,22(9):606-609
Analysis of the isobutane chemical ionization mass spectra of hexenols, cyclohexenols and various syn/anti pairs of bicyclic and tricyclic homoallylic alcohols shows that: (i) the spectra of the allylic alcohols are dominated by [M + H – H2O]+ and [M + C4H9–H2O]+ ions and contain traces of [M + H]+ ions; (ii) [M + H]+ ions are prominent in the spectra of acyclic and certain cyclic homoallylic alcohols; and (iii) [M + H]+ ions dominate the spectra of other acyclic unsaturated alcohols. The [M + H]+ ions may result from either: (a) protonation of the hydroxyl group, followed by a very rapid intramolecular proton transfer from the protonated hydroxyl group to the carbon–carbon double bond or internal solvation of the protonated hydroxyl group by the carbon–carbon double bond; and/or (b) direct protonation of the carbon–carbon double bond with significant internal solvation of the resulting carbocation by the hydroxyl group, which may lead to carbon–oxygen bond formation to give a protonated cyclic ether. The consequences of placing various geometric constraints on the possible intramolecular interactions between the hydroxyl group and the carbon–carbon double bond in unsaturated alcohols are explored. 相似文献