Molecular Weight Determination of Bisbenzylisoquinoline Alkaloids by 252Cf-Plasma Desorption Mass Spectrometer.
Hiroyuki KohnoShinobu TatsunamiTomoko HiroiHiroshi KouyamaMasashi TaniguchiNagasumi YagoIwao Nakamura
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Abstract:
Bisbenzylisoquinoline alkaloids of Stephania cepharantha have been used for various clinical purposes and recently reevaluated as stimulators of interleukin secretion in tissues. We analyzed molecular structures of bisbenzylisoquinoline alkaloids by determining their molecular weights using the 252Cf-plasma desorption mass spectrometry (PDMS) . The spectra were accumulated for 500000 fission events. The acceleration voltage used here was 15kV. Samples were analyzed using nitrocellulose-coated sample targets. Of the 5 alkaloids studied here, cepharanthine gave a main peak of molecular weight of 606.1 for the theoretical molecular weight of 606.7. The other minor peaks were considered to be demethylated fragment ions.252Cf-PDMS should be quite useful in studying structure, metabolism and pharmacokinetics of various drugs with extremely low coefficients of variation.Keywords:
Molecular mass
The observed fragmentations in collisionally activated dissociation (CAD) spectra of CX+ adduct ions formed in the fast atom bombardment (FAB) mass spectra of C2+2X- bisammonium salts are the same as those previously put forward to account for the FAB mass spectra of these compounds. Thus, substitution and elimination reactions occur in the gaseous phase between X- anions and C2+ cations, this being a new example of chemical reactivity in the gaseous phase in mass spectrometry. Furthermore, it was established that charge-remote fragmentations of these C2+2X- salts observed by mass spectrometry provide ions which allow aliphatic chain identification. These ions are as abundant in the FAB mass spectra as in the CAD spectra. © 1997 by John Wiley & Sons, Ltd.
Fast atom bombardment
Reactivity
Collision-induced dissociation
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Soft laser desorption
Deposition
Thermal desorption spectroscopy
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Collision with gas molecules can be used to add internal energy to gaseous ions in transit through a mass spectrometer, causing their subsequent unimolecular decomposition. Mass analysis of the resulting fragment ions produces a collisional activation mass spectrum whose utility is basically similar to that of a normal mass spectrum. Promising applications to date have been found in ion structure characterization for fundamental studies and molecular structure determination, for which the insensitivity of the collisional activation mass spectrum to the ion’s internal energy is a unique advantage; examples are given for structure determination of C 7 H 7 + and CSH 3 + isomers. An additional application attracting increasing attention is as a separation/identification technique for complex mixtures; this involves mass spectrometric separation of the ionized mixture components followed by their identification from the corresponding collisional activation (or metastable ion) mass spectra. This two-dimensional mass spectrometry (‘m.s.-m.s.’) technique is complementary to g.c.-m.s. and liquid chromatography - mass spectrometry, and its use is illustrated by the determination of trace components in gasoline and the chirality of organophosphates.
Polyatomic ion
Collision-induced dissociation
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Using the absorption and desorption experiments of No.3 coalbed of the Sihe coal mining,discuss how the temperature changes affect desorption of coalbed methane,and reach three important conclusions:①With increasing temperature,the desorption rate has increased,and the desorption will be inhibited when the temperature reduces;②During the step-down desorption process,desorption volume are larger at low-pressure phase;③From 22 ℃ to 38 ℃,the desorption rate has increased by4.5%/3 ℃,the effect of temperature rise on desorption is much more sensitive than pressure reduces.
Coalbed Methane
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Desorption of indigosol blue from humic acid coated Fe3O4 (Fe3O4-HA) was investigated. The desorption had been done with HCl as desorption agent. The purpose of this study was to determine the effect of various concentration HCl on desorption efficiency of indigosol blue from Fe3O4-HA. Desorption was carried out during 60 minutes of contact time.The result confirmed that HCl can be used as desorption agent although complete desorption can not be achieved, the desorption efficiency was 48.52 % with concentration of HCl 1 M.
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Hybrid mass spectrometer
Quadrupole mass analyzer
Mass
Time-of-Flight
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Researches the desorption factors influencing the adsorption of heavy metal in sewage with immobilized yeast.The experimental results show that with HCl of 0.1 mol/L as strippant,the desorption rate of Pb2+ is 79.00%,desorption rate of Cu2+ is 67.72%,desorption rate of Zn2+ is 63.45%,and the desorption rate of Cd2+ is 72.03% when the desorption temperature is 36 ℃ and desorption time is 0.5 h.
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