A study of resonance electron capture ionization on a quadrupole tandem mass spectrometer

Procedures that allow the realization of resonance electron capture (REC) mode on a commercial triple-quadrupole mass spectrometer, after some simple modifications, are described, REC mass spectrometry (MS) and tandem mass spectrometry (MS/MS) experiments were performed and spectra for some compounds were recorded. In particular, the charge-remote fragmentation (CRF) spectra of [M - H](-) ions of docosanoic and docosenoic acids under low-energy collisionally activated dissociation (CAD) conditions were obtained, and showed that there were no significant differences for [M - H](-) ions produced at different resonances (i,e. for [M - H](-) ions with different structures). This observation was explained on the basis of results obtained from deuterium-labeled fatty acids, which showed that different CRF ions (but with the same m/z value in the absence of labels) could be produced by different mechanisms, and all of them were obviously realized under CAD conditions that made spectra practically indistinguishable. The other example, which compared the REC-MS/MS spectrum of [M - H](-) ions and EI-MS/MS spectrum of M+. ions of daidzein, demonstrated the potential of the REC-MS/MS technique for more complex structure elucidation. Copyright (C) 2000 John Wiley & Sons, Ltd.

Studies on the adduct reaction of disubstituted benzenes with ion system of acetone in gas phase

Ion - molecule reactions of disubstituted benzene with ion system of acetone and deuterium - labelled acetone under chemical ionization conditions were examined and the fragmentation reactions of the adduct ions formed by the ion - molecule reactions were studied using collision - induced dissociation (CID) technique. It was found that the electron - releasing groups favored the adduct reactions, whereas the electron - withdrawing groups did not. The position and properties of substituted groups affected the relative abundance of the adduct ions. The fragmentation reaction of the adduct ion formed by ortho - phenylenediamine with acetyl ion was similar to the reductive alkylation reaction of amine in condensed phase.

Studies of the ortho effect in fragmentations of acetyl ion adducts of disubstituted benzenes

The ion-molecule reactions of disubstituted benzenes under chemical ionization conditions with acetyl chloride as reagent gas were examined, and the fragmentation reactions of the adduct ions (mostly proton and acetyl ion adducts) were studied by collision-induced dissociation. Electron-releasing substituents favored the adduct reactions, and electron-withdrawing groups did not. The position and properties of substituting groups had an effect on the relative abundances of the adduct ions. Several examples of the ortho effect were observed. The fragmentation reaction of the adduct ions formed by ortho-benzenediamine with the acetyl ion was similar to the reductive alkylation reaction of amines in the condensed phase. Copyright (C) 2001 John Wiley & Sons, Ltd.

H/D exchange reaction of cyclopropane derivatives in the ion system of CD3OD

The fragmentation properties of the product ions [M + 1](+), [M + 2](+) and [M + 3](+) formed by ion-molecule reaction of four cyclopropane derivatives with the ion system of CD3OD were investigated by using collision-induced dissocation technique. The experiment results indicated that the product ions were produced via the H/D exchange reaction between reactants and reactive reagent ions of CD3OD. There are two exchangable hydrogen atoms on the ring of compounds 1 and 2, and only one for compound 3 and 4.

Synthesis of monodisperse pheyl-capped oligoaniline pentamer and hexamer in the leucoemeraldine oxidation state and EB state and its UV studies

Aniline pentamer and hexamer in the leucoemeraldine oxidation state were synthesized through a novel method. The method was accomplished by the reaction of parent aniline tetramer in the pernigraniline oxidation state with diphenylamine and N-phenyl-1,4-phenylenediamine in the leucoemeraldine oxidation state respectively. The oligomers in the leucoemeraldine oxidation state were characterized by IR, NMR, elemental analysis and MALDI-MS. Aniline pentamer and hexamer in the emeraldine oxidation state were synthesized by the oxidation of Ag2O in DMF. It was found that some fragmentation occurred when the pentamer and hexamer were oxidized by (NH4)(2)S2O8 and FeCl3. 6H(2)O. The pentamer and hexamer in the emeraldine oxidation state was studied by UV/Vis spectra. The relative intensity of exciton peak for pentaaniline showed a little increase compared with that of hexaaniline.

Application of acetone and dimethyl ether chemical ionization reagent gases to structural analysis

Acetone and dimethyl ether( DME) have been shown to be reagent gases of exceptional utitlity and versatility for the characterization of a variety of class of organic compounds. The fragmentation mechanisms of the adduct product ions, formed by ion/molceule reaction of the substrate with the ionized gases, have been studied and substantiated by experiments with acetone-d(6) and DME-d(6).

Electrospray ionization multiple-stage tandem mass spectrometric analysis of diglycosyldiacylglycerol glycolipids from the bacteria Bacillus pumilus

Electrospray ionization (ESI) combined with multiple-stage tandem mass spectrometry (MSn) was used to directly analyze the glycolipid mixture from bacteria Bacillus pumilus without preliminary separation. Full scan ESI-MS revealed the composition of picomole quantities of glycerolglycolipid species containing C-14-C-19 fatty acids, some of which were monounsaturated, Two main components were identified from their molecular masses and fragmentation pathways. The fragmentation pathway of the known compound compared with the investigated compound verified the proposed structure as 1(3)-acyl-2-pentadecanoyl-3(1)-O-[beta-D-glucopyranosyl-(1-->6)-O-beta-D-glucopyranosyl]-sn-glycerols. A comparison of the multiple tandem mass spectra of the different alkali-metal cation adducts indicates that the intensity of fragments and the dissociation pathways are dependent on the alkali-metal type, The basic structures of glycerolglycolipids were reflected clearly from the fragmentation patterns of the sodium cations, The intense fragments of the sugar residue from the precursor ions were obtained from the lithiated adduct ions. ESI-MSn spectra of [M + K](+) ions did not provide as much fragmentation as [M + Na](+) and [M + Li](+) adducts, but their spectra allow the position of glycerol acylation to be determined. On the basis of MS2 spectra of[M + K](+) ions, it was established that all components have a C-15:0 fatty acid at the sn-2 position of the glycerol backbone and C-14-C-19 acids at the sn-1 position of the glycerol backbone. Copyright (C) 1999 John Wiley & Sons, Ltd.

Studies on electrospray mass spectrometry of some narcotic drugs

Using electrospray ionization (ESI) and tandem mass spectrometry techniques, the protonic positions in protonated molecular ions of some narcotic drugs were studied, The data of ESI/MSn experiments of morphine and deuterium-loaded morphine were first discussed. The protonic position was considered to locate on oxygen atom of cyclic ether in morphine molecular, Compared with the same and different: ions among morphine, codeine, acetylcodeine and dihydrocodeine, the protonic positions in protonated molecular ions of these compounds were further determined. The fragmentation mechanism of morphine in ESI/MSn: experiments was also repored in the paper, and there were similar dehydrolysis mechanism in gas phase or in liquid phase for morphine.

Investigation of the structures of the product ions produced via self-CI of acetone

The ion-molecule reactions in acetone were investigated which were induced under the chemical ionization. The structural information of the reaction products were obtained by using collision-induced dissociation (CID) technique performed at ion kinetic energies of 30eV.

Rapid analysis of steroidal saponin mixture using electrospray ionization mass spectrometry combined with sequential tandem mass spectrometry

Using electrospray ionization mass spectrometry (MS) combined with sequential tandem MS(ESI-MSn), two major steroidal saponins extracted from Tribulus terrestris were studied, and considerable useful structural information was obtained. The structure of the proposed known steroidal saponin was verified, and the structure of the unknown saponin was investigated using MSn experiments. Some special fragment ions were also observed, and the corresponding fragmentation mechanisms were investigated which are characteristic for steroidal saponins and can give some information on the linkage position of some sugar groups in saponins. This methodology has been established as a powerful tool for the rapid, comparative analysis of mixtures such as crude plant extracts. (C) 1998 John Wiley & Sons, Ltd.

Recent development of intermediate ion/neutral complexes

The fundamental aspects of ion/neutral complex as an important intermediate of unimolecular fragmentation in mass spectrometry have been summarized in this review, especially for the classified description of its formations, characteristics, reactions, investigation methods, recent achievements and application. Meanwhile, another kind of proton-bound complex, which is a special type of ion/neutral complex, has been also introduced briefly. Among them, a part of authors' work was included.

Structure of [C8H7](+) and intramolecular proton transfer reactions in 3-phenyl-1-butyn-3-ol by MS/MS technique

The electron impact mass spectrum (EIMS) of 3-phenyl-1-butyn-3-ol was reported in this paper. Collision-induced dissociation (CID) was used to study the gas phase ion structure of [C8H7](+) formed by the fragmentation of ionized 3-phenyl-1-butyn-3-ol, and that it has the same structure as m/z 103 ions generated by cinnamic acid and alpha-methylstyrene. Deuterium labelling, metastable ion (MI) and CID experimental results indicate the formation of m/z 103 ion resulting from molecular ion of 3-phenyl-1-butyn-3-ol, which is a stepwise procedure via twice proton transfers, rather than concerted process during the successive elimination of methyl radical and neutral carbon monoxide accompanying hydrogen transfer. Moreover, in order to rationalized these fragmentation processes, the bimolecular proton bound complex between benzyne and acetylene intermediate has been proposed.

Fragmentations of some bifunctional phenylether compounds by intermediate ion/neutral complexes

The fragmentations of three bifunctional phenylether compounds including 2-(2, 6-dichloro)phenoxyl propionitrile, N-hydroxyl-4-butoxyl phenylacetyl amine(bufexamc) and 2-(1-methylethoxyl) phenol methylcarbamate (Propoxur) under electron impact ionization were reported, Metastable ion(MI) and collision-induced dissociation(CID) at a low energy have been used to study the fragmentation pathways from molecular ions. Apart from the simple bond cleavages, and the unimolecular dissociations via ion/neutral complex intermediate as a competitive mechanism were demonstrated, Moreover, the intramolecular hydrogen transfer and double hydrogen transfers in the fragmentations of these compounds were discussed in detail.

CHEMICAL-IONIZATION MASS-SPECTROMETRY OF SOME NITRO-CONTAINING BIFUNCTIONAL AROMATIC-COMPOUNDS - LOCATION OF PROTONATION SITE

It is found that the nitro substituent of some aromatic bifunctional compounds shows unusual reactivity towards protonation. In the chemical ionization mass spectra of nitrobenzoic acids and their esters and amides, and of nitrophenols and their ethers, protonations on the carboxyl, ester, amide, hydroxyl or alkoxyl groups are highly suppressed by that on the nitro group. As a result, fragmentations based on protonation on these groups unexpectedly become negligible. Ortho effects were observed for all the ortho isomers where the initial protonation on the nitro group is followed by an intramolecular proton transfer reaction, which leads to the expected 'normal' fragmentations. Protonation on the nitro substituent is much more favourable in energy than on any of the other substituents. The interaction of the two substituents through the conjugating benzene ring is found to be responsible for this 'unfair' competitive protonation. The electron-attracting nitro group strongly destabilizes the MH+ ions formed through protonation on the other substituent; although the COR (R = OH, OMe, OEt, NH2) groups are also electron-withdrawing, their effects are weaker than that of NO2; thus protonation on the latter group produces more-stable MH+ ions. On the other hand, an electron-releasing group OR (R = H, Me, Et) stabilizes the nitro-protonated species; the stronger the electron-donating effect of this group the more stable the nitro-protonated ions.

THERMAL-DECOMPOSITION PROCESSES OF SOME ELECTRICALLY CONDUCTING POLYMERS INVESTIGATED BY DIRECT PYROLYSIS MASS-SPECTROMETRY

Thermal decomposition processes of poly(thio-1,4-phenylene) (PPS), polythiophene (PT) and polyaniline (PAn) were investigated by direct pyrolysis EI or CI mass spectrometry (DPMS). They can provide up to heptemer pyrolynates and give some structure properties. The results indicate that the thermal degradation all undergoes in radical decomposition, PPS pyrolyzes into linear and cyclic oligmers, but PT and PAn pyrolyze only into linear oligmers.