摘要:

AbstractWith a membrane made of a relatively polar material, membrane‐inlet mass spectrometry can be used to measure the water activity in organic liquids of low dielectric constant. The detection limit for water depends on the solubility of water in the organic liquid. In butanol, hexanol, octanol and octane the detection limits at 45°C are 7, 4, 3 and 0.3 ppm, respectively. The half‐time of the water reponse at 45°C is 20 s. The method can be used for continuous monitoring of water in reaction systems in organic solvents. Examples given are the condensation of 2,4‐dimethyl‐3‐pentanone with phenylhydrazine in hexanol solution and the hydrolysis of acetylchloride in octa

ISSN:0951-4198    

DOI:10.1002/rcm.1290051002

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractThe mass spectrum of mercury/cesium complex clusters (Hg)nCs+is observed up tom/z=118 000 (n = 590). Singly charged clusters are produced by Cs+ion bombardment. The presence of an alkali metal in the ionization process yields cluster ions of the form (Hg)nX+. The clusters are analysed using the grand‐scale mass spectrometer, GEMMY, at Osaka University. The mass resolution of the instrument is high enough to resolve each cluster up tom/z=70 000. From the pattern of cluster distribution, the structrues of the large clusters can be studied. The number of Hg groups in metastable decay increases with the cluster sizen. The ion intensities of the mercury/cesium clusters are much stronger than that from CsI (used for mass calibration). The mass spectrum of the clusters can therefore easily be utilized for direct mass calibration up tom/z=70 00

ISSN:0951-4198    

DOI:10.1002/rcm.1290051003

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractA new ion desorption method is described that utilizes a primary beam of massive, multiply charged cluster ions to generate secondary ions of peptides in a glycerol matrix. The massive cluster ion beam is generated via electrohydrodynamic emission using a 1.5 M solution of ammonium acetate in 30% aqueous glycerol. Negaitve ion spectra of peptides obtained using this technique show greatly decreased relative intensities for fragment ions and ‘chemical noise’ background when compared to spectra obtained using a xenon atom primary beam. The near absence of fragmets derived from radiation damage to the sample solution is attributed to the impact of primary particles with energies less than 1 eV/nucl

ISSN:0951-4198    

DOI:10.1002/rcm.1290051004

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractAn oxonium ion atm/z317 is present in the desorption electron ionization and ammonia desorption chemical ionization mass spectra of peracetylated disaccharides, comprised of glucopyranose units linked (1 → 2), (1 → 3), (1 → 4) and (1 → 6), but is absent in the spectra of the (1 → 1)‐linked isomer. The ion aatm/z317, which is derived from the reducing moiety, has an O‐formyl group at the position of linkage to the non‐reducing moiety, and O‐acetyl groups at each of the remaining positions. The iosmeric monoformyl, triacetyl oxonium ions (atm/z317), derived from the (1 → 2)‐, (1 → 3)‐, (1 → 4)‐ and (1 → 6)‐linked disaccharides, give distinctly different mass‐analysed ion kinetic energy spectra, thereby enabling the linkage po

ISSN:0951-4198    

DOI:10.1002/rcm.1290051005

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractTwo simple models which Correspond more closely to physical reality than some prior models are proposed to account for the Coulomb‐induced frequency shifts to lower frequency, Which have been observed in Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometry. The first model consists of two different‐mass point charges which undergo cyclotron orbits with the same orbit centers at their respective cyclotron frequencies. The model predicts that each excited cyclotron motion should induce a negative frequency shift in the other's cyclotron motion. The model predicts a zero frequency shift for ions of the same mass. The physical basis for the Coulomb‐induced shift is most easily seen in a coordinate frame which rotates at the cyclotron motion of the ion whose frequency is shifted. It is noted that a prior model for Coulomb‐induced frequency shifts is more appropriate for scanning ICR than FT‐ICR and the reason is described for the correctness of the predictions of this less appropriate model. A second model, the line model, is created by extension of the point model. The line model gives rise to a position‐dependent frequency shift which is synonymous with inhomogeneous Coulomb broadening. When a non‐quadrupolar electrostatic trapping field is included in the model, ‘like’ ions become ‘unlike’ and Coulomb‐shifting and Coulomb‐broadening apply, as for ‘like’ ions. The analysis predicts that ICR cells which are designed to have negligible trapping fields over most of their volume will be less sensitive to Coulomb shifting/bro

ISSN:0951-4198    

DOI:10.1002/rcm.1290051006

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractTwo underivatized glycosphingolipids, Leband Ley, isomeric in carbohydrate structure (Fucα1 → 2Galβ1 → 3[Fucα1 → 4]GlcNAcβ1 → 3Glcβ1 → 4Glcβ1 → 1Cer and Fucα1 → 2Galβ1 → 4[Fucα1 → 3]GlcNAcβ1 → 3Galβ1 → 4Glcβ1 → 1Cer, respectively), were analyzed by positive‐ion fast‐atom bombardment (FAB) mass spectrometry with high energy collision‐induced dissociation (CID) and linked scanning. The two isomers were distinguishable by the abundance of product ions derived from the non‐reducing terminal tetrasaccharide fragment via sequential β‐eliminations of vivinaliy linked saccharide residues. Following earlier studies from other laboratories, which have dealt primarily with positive‐ion FAB‐CID mass spectrometry of simple model oligosaccharides, these results exemplify the practical application of two‐sector methodology to underivatized complex glycocon

ISSN:0951-4198    

DOI:10.1002/rcm.1290051007

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractThe utility of the thermospray mass Spectrometry (TSMS), fast‐atom bombarment mass spectrometry (FABMS), and elctropray mass spectrometry (ESMS) for the analysis of Fumonisin B1is investigative. In Additional, the analysis of two stanards of Fumonisim B1as well as an inculated corn culture extract that contained Fumonism B1is reported. The result of these efforts show that ESMS, as Well as FABMS and a combination of FAB and tandem mass spectrometry (FABMS/MS), provide useful data for the characterization of Fumonisin B1. The detection limit was 50 pg for Fumonism B1when analyzed by full scan FABMS, and 5 pg when analyzed by single‐reaction monitoring FABMS

ISSN:0951-4198    

DOI:10.1002/rcm.1290051008

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractThe magic bullet matrix shows a noticeable and specific reactivity towards two organometallic anions (borate and silicate). Thus, before selecting this matrix to study organic salts by fast‐atom bombardment mass spectrometry, it is necessary to check for this specific reactivit

ISSN:0951-4198    

DOI:10.1002/rcm.1290051009

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractThe fullerences C60and C70form adducts with toluene, p‐xylene and other aromatic compounds when refluxed in these solvents in the presences of FeCl3. Benzene derivatives are produced only when bromine is also present. Mass spectra of the reaction mixtures indicate the presence of derivatives including 1:1 adducts, as well as products of multiple additions of the aromatic molecules and their dehydrogenation products. Tandem mass spectrometry provides evidence for CC bonds formation between the adducts and fulleren

ISSN:0951-4198    

DOI:10.1002/rcm.1290051010

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY

摘要:

AbstractMultiple‐coincidence techniques involving detection of two near‐threshold electrons in coincidence with each other and with product ions are proposed to measure spectra of doubly charged ions and the decay of their energy‐selected states. The new techniques are demonstrated by laboratory experiments on double photoionization of CO2an

ISSN:0951-4198    

DOI:10.1002/rcm.1290051011

出版商:Heyden&Son Limited    

年代:1991

数据来源: WILEY