Accurate Mass Determination of Amino Alcohols by Turboionspray／Time—of—Flight Mass Spectrometry

ＩｎｔｒｏｄｕｃｔｉｏｎＡｍｉｎｏａｌｃｏｈｏｌｓａｒｅａｎｉｍｐｏｒｔａｎｔｃｌａｓｓｏｆｃｏｍｐｏｕｎｄｓｉｎｓｙｎｔｈｅｔｉｃｏｒｇａｎｉｃｒｅａｃｔｉｏｎｓ .Ｔｈｅｉｒｍｏｌｅｃｕｌｅｓｔｒｕｃｔｕｒｅｓｂｅｃｏｍｅｕｎｓｔｅａｄｙｗｈｅｎａｎａｌｙｚｅｄｂｙｅｌｅｃｔｒｏｎｉｍｐａｃｔ(ＥＩ) .ＴｈｅｆｒａｇｍｅｎｔｓｏｂｔａｉｎｅｄｆｒｏｍＥＩａｒｅｕｓｕａｌｌｙａｓ ｓｉｇｎｅｄｔｏｎｅｕｔｒａｌｌｏｓｓｅｓｓｕｃｈａｓＨ2 Ｏ ,ＣＨ3 ＯＨ (Ｆｉｇ .1) .ＥＩｉｓｎｏｔａｕｓｅｆｕｌｍｅ…     

Comparision of FAB and MALDI Mass Spectrometry of Ginsenosides

ＣｏｍｐａｒｉｓｉｏｎｏｆＦＡＢａｎｄＭＡＬＤＩＭａｓｓＳｐｅｃｔｒｏｍｅｔｒｙｏｆＧｉｎｓｅｎｏｓｉｄｅｓ￥ＺｈｏｕＹｕ；ＬｉｕＺｈｉｑｉａｎｇ；ＳｏｎｇＦｅｎｇｒｕｉ；ＬｉｕＳｈｕｙｉｎｇ；ＬｉＸｉａｎｇｇａｏ；ＹｉｎＪｉａｎｇｙｕａｎ（１Ｃｈａ...     

Sequence Analysis of Polypeptide by Mass Spectrometry

The method described in this work provides a sensitive and fast technique for investigating the primary structure of peptides with molecular weight up to 3340 amu. Usually, the metastable ion kinetic energy spectra (MIKES) and collisional activated decomposition (CAD) spectra provide complementary information for the FAB mass spectra, the MIKES and CAD spectra generally contain high-mass sequence ions.     

Mass Spectrometry and Liquid Chromatography - Mass Spectrometry of β-Amino ß-Nitrostilbenes

Abstract

(Z)-α-amino ß-nitrostilbenes are obtained by the reaction of either ammonia or primary or secondary amines on (Z)-α, ß-dinitrostilbene (DNS). The fragmentometric study of these compounds by electron impact and chemical ionization was carried out. The conditions in which it may be possible to determine the purity of these compounds were obtained by HPLC on reversed phase.

However the resolution factor between DNS and benzyl- or phenyl-aminonitroenamine is not sufficient for UV detection; only liquid chromatography-mass spectra coupling with negative ionization enables the detection of the possible presence of DNS in these nitro enamino derivatives.     

Chemical Ionization Mass Spectrometry of Pertrimethylsilylated Desulphoglucosinolates

IntroductionRapeseedisanimportantsource0fedibleoilintheworld.Themeal(residueafterbeingde-fatted)containsab0ut40%ofnutritionallyvaluableprotein.Unfortunately,itsusehasbeenlindtedbythepresence0fglucosinolates.Glucosinolates(GS)aresulfur-c0ntalningorganiccompounds,whichcommonlyoccurinspeciesofcrucderaecrops(e.g.mustard,rape,cabbage)andareresponsibleforthepungentodorandshmptaste.However,anumberofGShavebeenass0ciatedwithtoxicityasitsbreakdownproductsinterferewiththyroidfunctions,resultinginreduce…     

Mass spectrometric study of amino acid–triethylborane chelates

Abstract  Synthesis of chelates from selected l-amino acids and triethylborane, and the mass spectra of the chelates, are described. Conditions for forming dimers between the chelates and the sodium ion are discussed, and structures are proposed for the dimers. Graphical abstract        

Studies on Electron Impact Mass Spectra of Some Anhydro-sugars

ＳｔｕｄｉｅｓｏｎＥｌｅｃｔｒｏｎＩｍｐａｃｔＭａｓＳｐｅｃｔｒａｏｆＳｏｍｅＡｎｈｙｄｒｏ┐ｓｕｇａｒｓ＊ＹＵＪｉａｎ－ｘｉｎ＊＊，ＬＩＵＹｕ－ｔｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，ＸｉｎｊｉａｎｇＵｎｉｖｅｒｓｉｔｙ，Ｕｌｕｍｕｑ...     

Electron Ionization Mass Spectrometry of Some Ferrocenyl Thia-crown Ethers

ＥｌｅｃｔｒｏｎＩｏｎｉｚａｔｉｏｎＭａｓＳｐｅｃｔｒｏｍｅｔｒｙｏｆＳｏｍｅＦｅｒｒｏｃｅｎｙｌＴｈｉａ┐ｃｒｏｗｎＥｔｈｅｒｓＳＵＪｉｎｇ－ｚｈｅａｎｄＪＵＹｉｎｇ（ＢｅｉｊｉｎｇＩｎｓｔｉｔｕｔｅｏｆＣｈｅｍｉｃａｌＲｅａｇｅｎｔｓ，Ｂｅｉｊｉ...     

The Coincidence of Mass Integrals g(α)

The idea of the generation of thermokinetic models on the basis of the analysis of kinetic equations (isothermal conditions) and thermokinetic equations (dynamic conditions) is presented. The method resembles that used in polisothermal conditions, which consists in analysis of the relation of the equilibrium conversion degree vs. temperature. The interpretation of the coincidence of mass integrals g(α) in the relation α vs. temperature has been attempted. This revised version was published online in August 2006 with corrections to the Cover Date.     

MALDI-TOF Mass Spectrometry Study of the Phosphorylated Tau Peptides

Fragmentation of phosphorylated Tau peptides in matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) has been investigated.According to the post-source decay (PSD) in MALDI-TOF-MS, there are two different patterns of cleavage in phosphopeptides, which can be used to determine the phosphorylated site in peptides.In the synthetic tau peptides, the fragmentation at proline residue occurs strongly and this is useful to determine the structure of tau peptides.     

Reconstructed Mass Spectra,A Novel Approach for the Utilization of Gas Chromatograph—Mass Spectrometer Data

Abstract

Peak profile analysis of each of the few hundred mass chromatograms generated during a complete GC-MS experiment identifies all m/e values which maximize at any of the few hundred consecutive mass spectra recorded during the gas chromatogram. The resulting sets of data correspond to the mass spectrum of each eluting component (even very minor ones) practically free of the contributions of unresolved companion substances, tailing fractions, column bleed, etc. These “reconstructed mass spectra” are therefore more easily interpreted or automatically identified than the mass spectra originally recorded. A plot of the summed abundance of the ions that maximize at a given spectrum index number (“mass resolved gas chromatogram”) results in a gas chromatogram of dramatically improved apparent resolution.     

Theoretical Study of the Sensitivity-Improvement Effect of Phosphoryl Group in Mass Spectrometry of Small Peptides

Mass spectrometry plays an important role in peptide sequencing since the invention of soft ionization techniques, such as fast atom bombardment (FAB), electrospray (ESI) and matrix-assisted laser desorption/ionization (MALDI). In our previous work, it was found that phosphorylation on the N-terminal of small peptides could enormously improve their sensitivity in FAB-MS1.To understand the sensitivity-improvement effect of phosphoryl group, the energies for the protonation of glycylglycin…     

Pyrolysis Mass Spectrometry Analysis of BF4 − Doped Polythiophene

Abstract

Pyrolysis of electrochemically prepared BF₄ ^? doped polythiophene (PTh) by direct insertion probe and Currie point pyrolysis gas chromatography mass spectrometry techniques indicated that thermal decomposition of PTh occurs in two steps. In accordance with literature results, the first step is assigned to the loss of the dopant, and the second step to the degradation of the polymer backbone producing segments of various conjugation lengths. At elevated temperatures, detection of products such as H₂S and C₂H₂ indicating cleavage of the thiophene (Th) ring was associated with a network structure. For the dedoped samples, a significant increase in the relative intensities of the peaks characteristic to the counter ion of the dopant, N(C₄H₉)₄ ⁺ pointed out the inward diffusion of (C₄H₉)₄N⁺ during the dedoping process.     

Electrospray Ionization Mass Spectral Characteristics of Polyamide Containing 1,4,7,10-Tetraazacyclododecane

The study of the fragmentations of the protonated molecular species[M H]~ and selected fragment ions al-lowed proposals for the main fragmentation pathways of the title compound.In order to better understand the frag-mentation pathways,the MS~3 and MS~4 spectra of the title compound were obtained.The main fragmentation path-ways occur by the cleavage of the C-CO bonds between N-methylpyrrole and carbonyl groups,CO-NH amidebonds,NH-C bonds between the NH groups and the N-methylpyrrole rings,and N-C bonds in1,4,7,10-tetraazacyclododecane.Electrospray ionization was proven to be a good method for the structural charac-terization and identification of this kind of compound.     

Investigation of Copolymers of Thiophene‐Functionalized Polystyrene with Pyrrole by Pyrolysis Mass Spectrometry

The thermal and structural characterization of electrochemically synthesized thiophene‐functionalized polystyrene and pyrrole (PS/PPy) and their copolymers were investigated by direct pyrolysis mass spectrometry. The pyrolysis data confirmed the growth of polypyrrole onto the pendant thiophene moiety of polystyrene. It is determined that the electrolytic film has different properties from the mechanical mixture and the related homopolymers.     

Mass spectrometric identification of double bond positional isomers of hexadecenyl acetate without chemical derivatization

A method for the identification of the double bond positional isomers of hexadecenyl acetate has been established by analysing similarity of the mass spectra patterns on a fuzzy classification, in which the intensity ratios of six diagnostic pairs of the predominant ions were selected as standard parameters for the characterization of the double bond position. The procedure was tested with △2 to △15-isomers of chemically unmodified hexadecenyl acetate, and the original double bond position in the acetates was located unambiguously.     

Determination of Pesticides in Carrots by Gas Chromatography–Mass Spectrometry

ABSTRACT

A sensitive and selective method was developed to determine pesticides in carrots by gas chromatography–mass spectrometry following the development of an optimized extraction procedure. The method was validated for 30 organochlorine pesticides for gas chromatography with electron capture detection obtaining limit of detection from 0.18 to 0.92?µg/kg except for cis- and trans-permenthrin. Twenty-six carrot samples were analyzed and six pesticides were detected. The results compared with the accepted maximum residue levels in correlation to crop origin.     

Intensity Exaggeration of Endohedral Metallofullerenes in Laser Desorption-Ionization Time-of-Flight Mass Spectrometry

Massspectrometryhasplayedacriticalroleinthefullereneresearchesl-8.ItwillalsobeheIpfulinthestudyofendohedralmetallofullerenes6.Eventhoughtherehavebeenplentyofreportsonmet.ll.fullerenes'-",detailedstudiesabouttheirgas-phasebehaviorareverypoor.Inthisletter,wereportanunusualintensityexaggerationphenomenonofendohedralmetallofullerenesinLD-TOFmassspectrometry,whichisconsideredduetotheirpeculiarionizationenergiesandelectronaffinities.SootcontainingmetallofullereneswassynthesizedbyK-Hcarbonarcevap…     

Novel Rearrangement of Small Peptides in Electrospray Ionization Tandem Mass Spectrometry

Electrospray ionization mass spectrometry (ESI-MS) is a powerful method for sequencing peptides. A novel fragmentation pattern with the loss of a neutral fragment of 45 Da was observed with the dipeptides, tripeptides,tetrapeptides and pentapeptides containing phenylalanine or histidine residues. A novel rearrangement reaction with the extrusion of a formamide piece was studied and the rearrangement mechanism was proposed and confirmed by deuterium labeling experiments with ESI-MS^n and high-resolution mass spectrometry. These findings are potentially helpful in identifying the specific sequence pattern in the peptide sequencing.     

Preliminary Characterization of the Composition and Phenolic Fragmentation of Olive Byproducts by Gas Chromatography–Mass Spectrometry and High-Performance Liquid Chromatography–Tandem Mass Spectrometry

Olive waste is a potential resource due to its rich variety of biologically active compounds. To investigate chemical components of olive waste, the selected samples were extracted using ultrasound assisted enzyme hydrolysis and petroleum ether, ethyl acetate and n-butyl alcohol were used to obtain a series of solvent extracts. Gas chromatography–mass spectrometry analysis showed hydrocarbons, esters, acids, alcohols, and ketones present in the extracts. Some fatty acids were considered to be predominant; it is noteworthy that phenolic compounds were detected in the ethyl acetate extract fraction. Furthermore, the primary phenolic compounds were also determined by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry. The possible fragmentation patterns have been proposed in positive and negative ion modes; the main fragment ions were observed from the loss of methyl, hydroxyl, or carboxyl groups. The compounds showed different fragmentation ions types in both positive and negative ionization modes and gave structural information on the main phenolic compounds in olive waste. The results of this study may be used to identify valuable active compounds and guide commercial applications of olive waste.