Electron Impact Ionization Mass Spectra Research Articles

Identification of free ceramide in human erythrocyte membrane.

Free ceramide was characterized in human erythrocytes and ghosts. Its concentration was found to be 5.6 mumol/100 ml of packed cells. It was isolated by thin-layer chromatography of its acetylated form and purified by thin-layer chromatography after deacetylation. It was constituted mainly of C16, C22, C24:0, and C24:1 nonhydroxy fatty acids and of C18:1 sphingosine. A small amount of 2-hydroxy fatty acids was also detected, containing mainly C24:0 hydroxy fatty acid. The structures of the ceramides and identification of the minor bases were confirmed by electron-impact and chemical ionization mass spectra of the trimethylsilylated ceramides.

Trace analysis of amines and isocyanates using glass capillary gas chromatography and selective detection : III. Determination of aliphatic and alicyclic amines as perfluoro fatty acid amides using electron-capture and nitrogen-selective detection

A method for the trace analysis of aliphatic and alicyclic amines is presented. It involves derivatization of the amines to the corresponding amides by reaction with a perfluoro fatty acid anhydride. The amines were separated by glass capillary gas chromatography and picogram amounts were quantitated using on-column injection and electron-capture or nitrogen-selective detection. The method was applied to amines of interest from work environment health aspects. Detection limits were in the 2–30 fmol range with electron-capture detection and in the 40–60 fmol range with nitrogen-selective detection. Linear ranges for the quantitative analysis were established and electron impact and methane chemical ionization mass spectra of investigated heptafluorobutyric acid amides were registered and discussed.

The electron impact and chemical ionization mass spectra of a series of 1‐alkyl‐1‐bromotetrachlorocyclotriphosphazines

Organic Mass SpectrometryVolume 18, Issue 4 p. 178-181 New Mass Spectra The electron impact and chemical ionization mass spectra of a series of 1-alkyl-1-bromotetrachlorocyclotriphosphazines Paul J. Harris, Corresponding Author Paul J. Harris Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USADepartment of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USASearch for more papers by this authorRobert D. Minard, Robert D. Minard Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802 USASearch for more papers by this authorHarry R. Allcock, Harry R. Allcock Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802 USASearch for more papers by this author Paul J. Harris, Corresponding Author Paul J. Harris Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USADepartment of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USASearch for more papers by this authorRobert D. Minard, Robert D. Minard Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802 USASearch for more papers by this authorHarry R. Allcock, Harry R. Allcock Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802 USASearch for more papers by this author First published: April 1983 https://doi.org/10.1002/oms.1210180411Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume18, Issue4April 1983Pages 178-181 RelatedInformation

Alkoxysilane elimination and its anomalous stereochemical behaviour for some ionized silane derivatives

The electron impact and chemical ionization mass spectra of several cyclopropyl (cyclopropenyl) silanes containing an ester (ether) group on the cyclopropyl ring has been studied. Trialkylalkoxysilane or disiloxane elimination from the molecular ion was found to be a main common fragmentation route. Surprisingly; this was more significant for the trans than for the cis isomers. This inverse stereochemical effect is explained in terms of a competitive alkyl elimination from the silicon atom, which involves neighbouring group participation for the cis isomers.

Mass spectrometric analyses of biologically active choline phospholipids and their lyso derivatives.

The electron impact and chemical ionization mass spectra of 1-O-hexadecyl- and 1-palmitoyl-2-O-acetyl-sn-glycero-3-phosphocholines and their lyso derivatives were measured by insertion of the compounds into a direct inlet system. The lysophospholipids were decomposed by heating at over 300°C into multiple compounds that volatilized together and gave several characteristic ion peaks when subjected to electron impact or interaction with an ion plasma of reactant gas. The mass spectral data indicated that the major pyrolysis products of these lysophospholipids were produced by elimination of methanol or N, N-dimethylethanolamine. When sn-2-acetyl phospholipids were introduced on the direct insertion probe and heated, several pyrolysis products volatilized together at above 350°C. The results suggested the major pyrolysis mechanism was loss of the phosphorylcholine moiety, together with some deacetylation and subsequent elimination of methanol and N, N-dimethylethanolamine from the sn-2-acetyl phospholipids.

The fast atom bombardment mass spectra of glucosinolates and glucosinolate mixtures

AbstractThe behaviour of glucosinolates and desulphoglucosinolates under fast atom bombardment conditions has been investigated. Relatively little fragmentation was noted in the mass spectra of these compounds. The positive ion fast atom bombardment mass spectra of glucosinolates exhibited abundant cationized and protonated molecula ions, thus complementing the previously reported electron impact and chemical ionization mass spectra of these compounds. Desulphoglucosinolates yield only the protonated molecular ion. Under negative ion conditions the spectra of glucosinolates were dominated by the molecular anion and this has been used as a means of analysing a crude plant extract containing a complex mixture of glucosinolates.

Mass-spectrometric characteristics of some pertrimethyl-silylated desulfoglucosinolates

The electron impact and chemical ionisation mass spectra of twelve pertrimethylsilyl derivatives of desulfoglucosinolates deriving from naturally occurring parent compounds are described and discussed. Series of characteristic ions, mostly comprising molecular ions, render mass spectrometry of such derivatives, in combination with gaschromatographic separation, a useful tool in the identification of known and novel glucosinolates. The scope of the method is wide though limitations exist. Thus, the extensive series of naturally occurring glucosinolates possessing methylsulphinyl-substituted side-chains undergo decomposition on attempted gas chromatography of their pertrimethylsilylated desulfoglucosinolate derivatives.

Electron impact, chemical ionization and field desorption mass spectrometry of substituted dihydroxyphenyl-benzodioxins isolated from insect cuticle. Occurrence of thermal decomposition and oligomerization reactions in the mass spectrometer.

The electron impact, field desorption and chemical ionization mass spectra of seven dihydroxyphenyl-benzodioxins isolated from insect cuticle are discussed. Reproducible electron impact and chemical ionization spectra are obtained as a result of thermal decomposition and either electron impact or chemical ionization. In some of the chemical ionization spectra dimerization of the thermal degradation products is observed. Structure determination is possible based upon the electron impact and field desorption spectra.

Dimeric epoxy fatty acid methyl esters: formation, chromatography and mass spectrometry

The formation of dimers is reported from the thermal treatment of a series of epoxy fatty acid methyl esters. These compounds were isolated from the reaction mixture by steric exclusion chromatography and were subsequently characterised by their high resolution electron impact and ammonia chemical ionisation mass spectra. The spectra were consistent in each case with the presence of a mixture of four possible positional isomers each containing an ether bridge linking a pair of fatty acid methyl esters across the carbon chains, with a keto group on a carbon adjacent to the bridge on one of the esters.

The electron impact and chemical ionization mass spectra of some glycidyl ethers

AbstractThe electron impact and chemical ionization mass spectra of a number of aliphatic and aromatic glycidyl ethers are reported. For electron impact spectra, partial fragmentation pathways have been determined by metastable linked scan techniques.

The electron impact and chemical ionization mass spectra of 2,2‐disubstituted 1,3‐benzodioxoles

Organic Mass SpectrometryVolume 15, Issue 8 p. 435-436 New Mass Spectra The electron impact and chemical ionization mass spectra of 2,2-disubstituted 1,3-benzodioxoles Josep J. Brophy, Corresponding Author Josep J. Brophy School of Chemistry, University of New South Wales, P.O. Box. 1, Kensington, NSW 2033, AustraliaSchool of Chemistry, University of New South Wales, P.O. Box. 1, Kensington, NSW 2033, AustraliaSearch for more papers by this authorGeorge Crank, George Crank School of Chemistry, University of New South Wales, P.O. Box. 1, Kensington, NSW 2033, AustraliaSearch for more papers by this authorHai Minh, Hai Minh School of Chemistry, University of New South Wales, P.O. Box. 1, Kensington, NSW 2033, AustraliaSearch for more papers by this authorDerek Nelson, Derek Nelson School of Chemistry, University of New South Wales, P.O. Box. 1, Kensington, NSW 2033, AustraliaSearch for more papers by this author Josep J. Brophy, Corresponding Author Josep J. Brophy School of Chemistry, University of New South Wales, P.O. Box. 1, Kensington, NSW 2033, AustraliaSchool of Chemistry, University of New South Wales, P.O. Box. 1, Kensington, NSW 2033, AustraliaSearch for more papers by this authorGeorge Crank, George Crank School of Chemistry, University of New South Wales, P.O. Box. 1, Kensington, NSW 2033, AustraliaSearch for more papers by this authorHai Minh, Hai Minh School of Chemistry, University of New South Wales, P.O. Box. 1, Kensington, NSW 2033, AustraliaSearch for more papers by this authorDerek Nelson, Derek Nelson School of Chemistry, University of New South Wales, P.O. Box. 1, Kensington, NSW 2033, AustraliaSearch for more papers by this author First published: August 1980 https://doi.org/10.1002/oms.1210150809Citations: 4AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article.Citing Literature Volume15, Issue8August 1980Pages 435-436 RelatedInformation

Electron impact and chemical ionization mass spectra of catechol derivatives from insect cuticle

Electron impact and isobutane chemical ionization mass spectra of a series of catechol derivatives isolated from hydrolysates of insect cuticle were studied. Electron impact mass spectrometry resulted in sufficient information for the identification of all the compounds. Furthermore, characteristic fragmentation patterns were demonstrated, which allow classification of the catechol derivatives according to the substituent next to the aromatioring of the aliphatic sidechain. By chemical ionization mass spectrometry [M + H]+ions were the base peak in most spectra, but for some compounds [M + H]+ was absent, and [M + H - H2O]+ the base peak. In many of the CI spectra [2M + H]+ ions were present and in one case [3M + H]+. Chemical ionization mass spectrometry was unsuitable for the identification of the catechol derivatives investigated.

Stereochemical applications of mass spectrometry: 1—The utility of electron impact and chemical ionization mass spectrometry in the differentiation of stereoisomeric benzoin oximes and phenylhydrazones

AbstractA study of the electron impact and chemical ionization (H2, CH4, and iso‐C4H10) mass spectra of stereoisomeric benzoin oximes and phenylhydrazones indicates that while the former can be distinguished only by their chemical ionization mass spectra the latter are readily distinguishable by both their electron impact and chemical ionization mass spectra. The electron impact mass spectra of the isomeric oximes are practically identical; however, the chemical ionization spectra show that the E isomer forms more stable [MH]+ and [MHH2O]+ ions than the Z isomer for which both the [MH]+ and [MHH2O]+ ions are relatively unstable. In electron impact the Z‐phenylhydrazone shows a lower [M]+˙ ion abundance and more facile loss of H2O than does the E isomer. This more facile H2O loss also is observed for the [MH]+ ion of the Z isomer under chemical ionization conditions.

Comparison of electron impact and chemical ionization mass spectra of some arenetricarbonylchromium complexes

The mass spectrometric behavior of a) the tricarbonylchromium complexes of a series of aromatic hydrocarbons, b) the dimethyldiphenyl compounds of the Group IV elements (i.e., diphenylpropane, dimethyldiphenylsilane, etc.) and c) the mono- and bis-tricarbonylchromium complexes of these ligands under electron impact and chemical ionization conditions are reported. The MH + ion is base peak for all of the simple arenetricarbonylchromium complexes using chemical ionization, whereas [ M — 3 CO] + or 52Cr + dominate the spectra with electron impact ionization. The chemical ionization spectra of the series of Group IV element ligands do not exhibit signals in the molecular ion region, the base peak being [ M — Ph] +. [ M — CH 3] + is the electron impact base peak for each of the ligands except the lead-containing compound, for which the base peak is 208Pb +. The mono-tricarbonylchromium complexes yield chemical ionization molecular ion clusters, but their base peaks arise via fragmentation of the Group IV element—aromatic ring bonds. Electron impact ionization spectra of the mono complexes are characterized by losses of CO and the production of Cr + ions, neither of which occurs with chemical ionization. For the series of bis-tricarbonylchromium complexes, an MH + ion is prominent only in the chemical ionization spectrum of the diphenylpropane complex. The electron impact induced spectra of the bis-tricarbonylchromium complexes are similar to those of the mono-complexes in that loss of CO is a prominent feature.

Direct Analysis of Polymer Chemical Mixtures by Field Desorption Mass Spectroscopy

Abstract Several examples have been given in which field desorption mass spectroscopy was very effective in the analysis of polymer chemical mixtures. The method has proved to be an excellent screening technique for initial examination of complex samples. Thus FD-MS data may be used as a basis for deciding whether further characterization by other spectroscopic or chromatographic techniques is necessary. In many cases, the FD molecular weights alone can quickly provide the data necessary for solution of a particular analytical problem. The fact that normally only one piece of data (the molecular ion) is provided for each component makes FD-MS unique in its ability to characterize polymer chemical mixtures. FD-MS is a very versatile tool that can be used in a number of practical applications of interest to the polymer chemist. On the negative side, it is evident that FD-MS by itself provides only limited chemical structure information. The molecular weight is provided and often nothing else. If this along with the history of the sample is not enough to deduce the structures present, then additional information must be obtained. Accurate mass measurements were used in several of the examples cited above. Isotope peaks for certain elements (e.g. S, Cl, Br) are often helpful, and electron impact (EI) and chemical ionization (CI) mass spectra may be obtained for the same samples. Other spectroscopic techniques (infrared and magnetic resonance) can be used to provide detailed structural information (e.g. isomerism and stereochemistry). Finally, chromatographic separations (GC, LC, GPC) may be necessary to isolate individual components for spectroscopic characterization. Field desorption may in some cases have other limitations that are not so obvious. The technique generally is not a good quantitative method although some promising work in this regard has appeared in the literature. The method is also compound selective; desorption rates and ionization efficiencies are quite dependent on molecular weight, volatility, chemical structure, and other factors. Certain types of highly polar compounds (underivatized carboxylic acids, for example) can be particularly troublesome. FD-MS operation at higher masses (MW > ∼ 2000) can be very difficult. Isomers which may be present are not distinguished since they have the same molecular weight. Finally, the method is not a “trace” technique in the modern sense of the word. Submicrogram quantities of pure materials can be examined, but for mixtures useful information may be lost for components present at levels less than ∼ 1–2% of the total. Nevertheless, we estimate that over 90% of the polymer chemical samples examined in our laboratory by field desorption have given good, readily interpretable FD mass spectra. Thus FD-MS has proven to be very effective tool for general characterization of these types of samples. The novel advantages of the method normally far outweigh its negative aspects and sometimes fickle reputation. Field desorption provides a very nice complement to structural data obtained by magnetic resonance, infrared, and electron impact mass spectroscopy. In most cases FD-MS can quickly provide chemical information on complex polymer chemical mixtures never before obtainable by any technique.

Isolation of 3-(2-carboxyethyl)thymine following in vitro reaction of β-propiolactone with calf thymus DNA

3-(2-Carboxyethyl)thymine (3-CET) was synthesized from β-propiolactone (BPL) and dThd5′P at pH 9.0–9.5 via the intermediate 3-(2-carboxyethyl)thymidine-5′-monophosphoric acid (3-CEdThd5′P). 3-CEdThd5′P was converted to 3-CET by hydrolysis in 1.5 N HCl at 100°C for 2 h. The structure of 3-CET was assigned on the basis of UV spectra, electron impact (EI) and isobutane chemical ionization mass spectra and the EI mass spectrum of a trimethylsilyl derivative of 3-CET. BPL was reacted in vitro with calf thymus DNA at pH 7.5. 100 A units of BPL-reacted DNA yielded, following perchloric acid hydrolysis and preparative paper chromatography, 3 A units of 3-CET. Reaction of BPL with the phosphodiester thymidylyl-(3′-5′)thymidine gave 3-(2-carboxyethyl)thymidylyl-(3′-5′)-3-(2-carboxyethyl)thymidine (∼3%). Phosphotriester formation was not detected.

Stereochemical effects in the mass spectra of 2‐hydroxy‐, 5‐hydroxy‐ and 2,5‐dihydroxyprotoadamantanes

AbstractElectron ionization and methane and isobutane chemical ionization mass spectra have been obtained for the four configurationally isomeric 2,5‐protoadamantanediols and the corresponding model monoalcohols. Although the electron impact (both 70 and 15 eV) and methane chemical ionization mass spectra of the 2,5‐protoadamantanediols are distinct, the variations are not large and in general they are difficult to rationalize in terms of specific structural features. In contrast, the isobutane chemical ionization mass spectra of these diols show significant differences which can easily be correlated with sterochemical orientations of the substituents.

Mass spectral identification of isomeric fluoronitroanilines

AbstractThe electron impact and methane chemical ionization mass spectra of 2‐fluoro‐5‐nitroaniline and 4‐fluoro‐3‐nitroaniline have been investigated. Similar fragment ions were observed for both compounds under electron impact conditions, but the difference in the relative ion intensities of two key fragment ions allowed the positive identification of these two isomers. The difference can be attributed to an ortho effect involving fluorine and the amino substituent. A fragmentation pathway consistent with this observation is suggested.

The electron impact and chemical ionization mass spectra of dimethyltrisulfide

The mass spectra obtained by electron impact ionization (EI) of dimethyltrisulfide, both at constant sample pressure and during elution from a GC column, are essentially identical, with the molecular ion Me2S3+ providing the basis peak. Masses heavier than the molecular ion are not observed. Chemical ionization, using nitrogen, methane or isobutane, gives rise to numerous ions of larger mass than that of the molecular ion. Particularly characteristic are sulfonium type structures Me3Sn+, with n=3–6. In addition, radical cations of the type Me3SnCH2+and protonated trisulfide, Me2S3H+, are observed, even with N2 as ionizing gas, together with a variety of ions of lower hydrogen content. Further, a large number of ion types of lower mass than the parent molecule are formed. The mass distribution of ions in the spectrum is found to be highly dependent on the partial pressure of dimethyltrisulfide in the ion source. These phenomena were investigated and accounted for semiquantitatively.

In vitro Dimroth rearrangement of 1-(2-carboxyethyl) adenine to N6-(2-carboxyethyl)adenine in single-stranded calf thymus DNA

The new adduct N 6-(2-carboxyethyl)adenine ( N 6-CEA) was prepared from 1-(2-carboxyethyl)adenine (1-CEA) by base catalyzed (Dimroth) rearrangement of 1-CEA. The structure of N 6-CEA was assigned on the basis of UV spectra and electron impact and isobutane chemical ionization mass spectra. When the carcinogen β-propiolactone was reacted in vitro with calf thymus DNA, 1-CEA but not N 6-CEA was detected on paper chromatograms following acid hydrolysis of the DNA. When BPL-reacted single-stranded DNA was incubated at pH 11.7 (37°C, 18 h) prior to acid hydrolysis, it was found that 1-CEA was completely converted to N 6-CEA in DNA by Dimroth rearrangement, whereas no conversion occurred at pH 7.5. The extent of Dimroth rearrangement at various pHs and temperatures was determined for 1-CEA, 1-methyladenine (1-MeA), 1-(2-carboxyethyl)-deoxyadenosine-5′-monophosphoric acid (1-CEdAdo5′P) and the phosphodiester 5′- O-(2-carboxyethyl)phosphono-1-(2-carboxyethyl)deoxyadenosine (1-CE-dAdo-5′-P-CE).