摘要:

AbstractDynamically correct (i.e., instrument‐independent) branching ratios can be measured under single‐collision conditions in tandem mass spectrometers incorporating RF‐only quadrupole collision cells. Theabsolutebranching ratios were measured as a function of the center‐of‐mass interaction energyECMfor the collisionally activated dissociation (CAD) of CH3CO+(m/z43) from several source compounds (ethanol, oxirane), and CH3CO‐X (where X = H, CH3, CH3CH2, CH3CO, CH3COCH2, and C6H5)). The energy dependences of the branching ratios for C2H3O+from CH3CO‐X source compounds are quite distinct from those observed for C2H3O+from ethanol or ethylene oxide, or for the C3H+7ions (alsom/z43) fromn‐pentane. Hence, one can use the CAD ofm/z43 to distinguish CH3CO‐X compounds from other source compounds, including sources of C3H7+ions. Therefore, the characteristic branching ratios of ionic substructures may provide for tandem mass spectrometry a „fingerprinting”︁ capability analogous to the use of group frequencies i

ISSN:0951-4198    

DOI:10.1002/rcm.1290031102

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractA study of the low‐energy collisional activation (CA) spectra of O‐ and N‐epoxypropyltetrahydroacridines has revealed that the two isomers show characteristic differences in their spectra. The CA spectra of the M+[MH], MH+[M + C2H5]+and [M + C3H5]+ions are di

ISSN:0951-4198    

DOI:10.1002/rcm.1290031103

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractDouble‐charge‐transfer spectroscopy has been used to confirm that CF+and CCI+can exist for times greater than several μs in electronically excited states. From the spectra obtained it was shown that those states are 4.7 ± 0.7eV and 3.3 ± 0.5eV above the ground states for CF+and CCI+, respectively. The experimental technique is quite sensitive to the detection of long‐lived excited states and it is shown for CCI+that the relative populations of the excited and ground states are markedly different when CFCI3and CF2ClCFCI2are used as the precursor molecules in the dissociative‐ionizati

ISSN:0951-4198    

DOI:10.1002/rcm.1290031104

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractSome of the factors that influence the reduction of disulfide‐containing peptides under fast‐atom bombardment have been investigated using two neurohormonal peptides that include disulfide bridges in their structures. Deaminoarginine‐vasopressin (DAVP) and arginine‐vasopressin (AVP) have been analyzed as their acetate and trifluoroacetate salts. Results obtained in a thioglycerol matrix indicate that the peptides analyzed as their acetate salts are completely reduced under bombardment, whereas the trifluoroacetate salts show little evidence of reduction. Addition of trifluoroacetic acid to the acetate sample prior to bombardment inhibits reduction whereas addition after bombardment shows no effect on the reduction, thereby indicating the irreversibility of the process. Time‐monitoring experiments conducted with the acetate salts of DAVP and AVP in common matrices such as thioglycerol, dithiothreitol + diethioerythritol, glycerol, hydroxyethyldisulfide and nitrobenzyl‐alcohol demonstrate an important effect of the chemical nature of the matrix on reduction. In matrices containing thiol groups, the reduction is extensive, whereas it is almost suppressed in matrices such as hydroxyethyldisulfide and nitrobenzylalcohol. However, the addition of trifluoroacetic acid to all of these matrices essentially eliminates reduction and provides measured isotopic peak ratios that are in agreement with theoretically calculated values for the

ISSN:0951-4198    

DOI:10.1002/rcm.1290031105

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractThe effect of surface activity differences of sodium alkybenzene sulfonate homologs on quantification by fast‐atom bombardment mass spectrometry is investigated. By using three stable‐isotope internal standards to bracket the chainlength distribution, accurate quantification of surfactant mixtures is achieved. With a single deuterated internal standard, skewing of the distribution occurs. The magnitude of the skewing depends on the concentration of the sample and signal‐averaging time. The use of model mixtures of pure surfactants and analysis of commercial surfactant mixtures is demonst

ISSN:0951-4198    

DOI:10.1002/rcm.1290031106

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper describes the use of electron ionization mass spectrometry for structural characterization of a mixture of glycosphingolipids from a single human kidney and presents mass spectrometric evidence for the presence of an eleven‐sugar glycolipid. A large amount of structural information is obtained from minor glycolipid constituents having long sugar chains by a fractional evaporation in the ion source, achieved by steadily increasing the ion‐source temperat

ISSN:0951-4198    

DOI:10.1002/rcm.1290031107

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

摘要:

AbstractAn ion chromatography/mass spectrometry system which makes use of a continuous‐flow fast‐atom bombardment probe, has been constructed and evaluated. Examples are given of applications to the analysis of inorganic anions (ion‐exchange chromatography), water soluble vitamins (ion‐pair chromatography) and glucose derivatives (ion‐excluson chroma

ISSN:0951-4198    

DOI:10.1002/rcm.1290031108

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

ISSN:0951-4198    

DOI:10.1002/rcm.1290031109

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

ISSN:0951-4198    

DOI:10.1002/rcm.1290031110

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY

ISSN:0951-4198    

DOI:10.1002/rcm.1290031112

出版商:Heyden&Son Limited    

年代:1989

数据来源: WILEY