Ion/molecule reactions with dimethyl ether and dimethyl-d6 ether: differentiation of four isomers contained in patchouli essential oil

Conversion of benzoic acid into phenol in an ITMS under CI-MSn conditions. Recognition of ortho-chlorobenzoyl derivatives

Isomeric chlorobenzoyl cations (m/z 139), under collision-induced experiments, fragment identically. Chlorobenzoyl cations can be efficiently converted into cholorophenol radical cations by the reaction with methanol in the ion trap analyzer under CI-MSn conditions. The substitution of the carbonyl group with a hydroxyl moiety is able to induce an ortho effect, which is absent in the startingortho-chlorobenzoyl cation. This transformation could be useful to recognize ortho-chlorinated benzoyl derivatives without the need of MS spectrum comparison of the whole set of isomers. The method reported in this study could be applicable to biologically active molecules that dissociate to form the chlorobenzoyl cations under CI or CI collision-induced dissociation conditions, such as indomethacin, the degradation products from the insect growth regulator 1-(2-chlorobenzoyl)-3-(4-chlorophenyl) urea, and lorazepam.

Evaluation of the α-phenylvinyl cation as a chemical ionization reagent for the differentiation of isomeric substituted phenols in an ITMS

Ion-molecule reactions between the α-phenylvinyl cation and isomeric naturally occurring phenols were investigated using a quadruple ion trap mass spectrometer. The α-phenylvinyl cation m/z 103, generated by chemical ionization from phenylacetylene, reacts with neutral aromatic compounds to form the characteristic species: [M + 103](+) adduct ions and the trans-vinylating product ions [M + 25](+) , which correspond to [M + 103](+) adduct after the loss of benzene. Isomeric differentiation of several ring-substituted phenols was achieved by using collision-induced dissociation of the [M + 103](+) adduct ions. This method also showed to be effective in the differentiation of 4-ethylguaiacol from one of its structural isomers that displays identical EI and EI/MS/MS spectra. The effects of gas-phase alkylation with phenylvinyl cation on the dissociation behavior were examined using mass spectrometry(n) and labeled derivatives. Copyright © 2015 John Wiley & Sons, Ltd.

Determination of hazardous volatile organic compounds in the Hoffmann list by ion-molecule reaction mass spectrometry

RATIONALE

Off-line gas or liquid chromatographic mass spectrometry techniques are the most widely used method for analysis of hazardous, carcinogenic volatile organic compounds (VOCs) in mainstream cigarette smoke. However, these conventional techniques can lead to modification of VOCs during sample preparation due to the high reactivity of VOCs. Thus, the development of on-line mass spectrometric methods for analysis of VOCs is desirable to circumvent this problem.

METHODS

The accurate identification of VOCs is a critical step in the analysis of cigarette smoke. Here, we use ion-molecule reaction mass spectrometry (IMR-MS) to study the behavior of standard VOCs in the Hoffmann list during this analytical procedure, and then to profile the VOCs in mainstream cigarette smoke using this on-line mass spectrometric method.

RESULTS

We first discuss and summarize the charge transfer (CT) ionization and further fragmentation of 20 standard VOCs in the Hoffmann list with the ion reagents Hg(+), Xe(+), and Kr(+). The IMR-MS instrument was then connected to a Borgwaldt-RM20H rotary smoking machine in order to study VOCs in mainstream cigarette smoke on-line. Using this procedure, more than 20 VOCs were identified by IMR-MS by comparison with experimental results obtained on standard VOCs.

CONCLUSIONS

The IMR-MS technique can potentially result in reduced molecular fragmentation during analysis of VOCs. However, significant fragmentation still occurs during IMR-MS when the ionization energy (IE) of the ion reagent is much higher than the IE of the VOC, given that excess energy is stored in the newly formed ion during CT ionization. Given that IMR-MS cannot distinguish between isobaric compounds or isomers, we summarize the possible overlapping mass peaks from these isobaric species that may be present in analyses of VOCs. Selection of the ion reagent for IMR-MS should be based on the need to ensure CT ionization of the analytes, as well as avoiding their severe fragmentation.

Gas chromatographic-ion trap mass spectrometric analysis of volatile organic compounds by ion-molecule reactions using the electron-deficient reagent ion CCl3(+)

When using tetrachloromethane as the reagent gas in gas chromatography-ion trap mass spectrometry equipped with hybrid ionization source, the cation CCl(3)(+) was generated in high abundance and further gas-phase experiments showed that such an electron-deficient reagent ion CCl(3)(+) could undergo interesting ion-molecule reactions with various volatile organic compounds, which not only present some informative gas-phase reactions, but also facilitate qualitative analysis of diverse volatile compounds by providing unique mass spectral data that are characteristic of particular chemical structures. The ion-molecule reactions of the reagent ion CCl(3)(+) with different types of compounds were studied, and results showed that such reactions could give rise to structurally diagnostic ions, such as [M+CCl(3) - HCl](+) for aromatic hydrocarbons, [M - OH](+) for saturated cyclic ether, ketone, and alcoholic compounds, [M - H](+) ion for monoterpenes, M(·+) for sesquiterpenes, [M - CH(3)CO](+) for esters, as well as the further fragment ions. The mechanisms of ion-molecule reactions of aromatic hydrocarbons, aliphatic ketones and alcoholic compounds with the reagent ion CCl(3)(+) were investigated and proposed according to the information provided by MS/MS experiments and theoretical calculations. Then, this method was applied to study volatile organic compounds in Dendranthema indicum var. aromaticum and 20 compounds, including monoterpenes and their oxygen-containing derivatives, aromatic hydrocarbon and sesquiterpenes were identified using such ion-molecule reactions. This study offers a perspective and an alternative tool for the analysis and identification of various volatile compounds.

Application of gas chromatography-hybrid chemical ionization mass spectrometry to the analysis of diclofenac in wastewater samples

Hybrid chemical ionization (HCI), a new and useful alternative to conventional chemical ionization mass spectrometry, has been applied to the analysis of the pharmaceutical diclofenac in wastewater samples. This technique takes advantage of the high versatility of ion trap (IT) spectrometers combined with external ionization sources. In hybrid configuration, reagent ions are generated in the external source through electron ionisation (EI) of a reagent gas. These reagent ions are then drawn into the ion trap and only those selected are allowed to react with analytes eluting from the GC column. These ion-molecule reactions create analyte ions which are held in the ion trap. In this study ion-molecule reactions between C(3)F(5)(+) cations, generated from perfluorotributylamine (FC43), and diclofenac molecules have been investigated. The observed reaction products were [M+C(3)F(5)-H(2)O](+) adduct ions, which result from the initial electrophilic addition of C(3)F(5)(+) cations to the diclofenac molecule followed by the rapid loss of H(2)O. Further fragmentation of these ions by MS/MS yielded enough daughter ions for a reliable identification of diclofenac in complex matrices. The GC-HCI-MS/MS method applied to wastewater samples provided highly enhanced selectivity and sensibility, with a detection limit in real samples of 3.0 ng/L, for a solid-phase extraction (SPE) pre-concentration factor of 400. Other performance characteristics of the method, such as linearity and precision were also satisfactory. Finally, the method was successfully applied to the analysis of wastewater samples taken from the effluent of an urban sewage treatment plant (STP).

Ion/molecule reactions in a miniature RIT mass spectrometer

Ion/molecule reactions were explored in a newly developed miniature mass spectrometer fitted with a rectilinear ion trap (RIT) mass analyzer. The tandem mass spectrometry performance of this instrument is demonstrated using collision induced dissociation (CID) and ion/molecule reactions. The latter includes Eberlin transacetalization reactions and electrophilic additions. Selective detection of the chemical warfare simulant dimethyl methyl phosphonate (DMMP) was achieved through selective Eberlin reactions of its characteristic phosphonium fragment ion CH3OP(+)(O)CH3 (m/z 93), with 1,4-dioxane or 1,3-dioxolane. Efficient adduct formation as a result of electrophilic attack by the phosphonium ion on various nucleophilic reagents, including 1,1,3,3-tetramethyl urea, methanesulfonic acid methyl ester, dimethyl sulfoxide and methyl salicylate, was also observed using the RIT device. The product ions of these reactions were analyzed using CID and the characteristic fragmentation patterns of the ionic addition products were recorded using multiple-stage experiments in the miniature RIT instrument. This study clearly demonstrates that a small, home-built, miniature RIT mass spectrometer can be used to perform analytically useful ion/molecule reactions and also that instruments like this have the potential to provide a portable platform for in situ detection of organophosphorus esters and related compounds with high specificity using tandem mass spectrometry.

Current literature in mass spectrometry

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of mass spectrometry. Each bibliography is divided into 11 sections: 1 Books, Reviews & Symposia; 2 Instrumental Techniques & Methods; 3 Gas Phase Ion Chemistry; 4 Biology/Biochemistry: Amino Acids, Peptides & Proteins; Carbohydrates; Lipids; Nucleic Acids; 5 Pharmacology/Toxicology; 6 Natural Products; 7 Analysis of Organic Compounds; 8 Analysis of Inorganics/Organometallics; 9 Surface Analysis; 10 Environmental Analysis; 11 Elemental Analysis. Within each section, articles are listed in alphabetical order with respect to author (3 Weeks journals - Search completed at 28th. June 2000)