Positive ion chemical ionization

Syka, J.E.P. Positive ion chemical ionization with an ion trap mass spectrometer. Finnigan MAT IDT 19. 

Proton transfer is one of the prominent representatives of an ion-molecule reaction in the gas phase. It is employed for the determination of GBs and PAs (Chap. 2.11.2) by either method the kinetic method makes use of the dissociation of proton-bound heterodimers, and the thermokinetic method determines the equilibrium constant of the acid-base reaction of gaseous ions. In general, proton transfer plays a crucial role in the formation of protonated molecules, e.g., in positive-ion chemical ionization mass spectrometry (Chap. 7). 

Note When a positive ion results from Cl, the term may be used without qualification nonetheless positive-ion chemical ionization (PICI) is frequently found in the literature. When negative ions are formed, the term negative-ion chemical ionization (NICI) should be used. [8]... 

Polley, C.W., Jr. Munson, B. Nitrous Oxide As Reagent Gas for Positive Ion Chemical Ionization Mass Spectrometry. Anal Chem. 1983,55, 754-757. 

Bergh C, Torgrip R, Ostman C (2010) Simultaneous selective detection of organophosphate and phthalate esters using gas chromatography with positive ion chemical ionization tandem mass spectrometry and its application to indoor air and dust. Rapid Commun Mass Spectrom... 

Agilent GC-MS ChemStation System equipped with capillary gas chromatograph HP 5972,5973, or 6890 series Agilent 6890 series autosampler. The GC-MS system is operated in the positive-ion, chemical-ionization mode the reagent gas is ammonia. The chromatographic parameters of the acquisition method, the sequence of SIM windows, and the ion species being monitored are listed in Tables 3.1.8 and 3.1.9. The total run time is 17.88 min. 

MS, Mass spectrometry El, electron impact Cl, chemical ionization MID, multiple ion detection PICI, positive-ion chemical ionization NICI, negative-ion chemical ionization SIM, selected ion nmonitoring TSP, thermospray PPINICI, pulsed positive ion-negative ion chemical ionization ECD, electron-capture detector NPD, nitrogen/phosphorous detector NSTD, nitrogen-selective thermionic detector FT-IR, Fourier transform infrared spectrometry. 

The more exothermic the reaction, the greater the degree of fragmentation. Endothermic reactions do not yield a protonated form of a sample therefore, the sample compound cannot be recorded. One can choose the proper reactant gas that will give the correct fragmentation pattern of a desired compound out of a mixture of compounds.13 Chapman3 lists positive ion chemical ionization applications by reagent gas and by compounds analyzed. The values are provided in kcal/mol for convenience to convert to the appropriate SI unit (kJ/mol), multiply by 4.1845. 

The following discussion will be concerned primarily with applications of the ms/ms technique in the synfuel area. Attempts will be made to illustrate the unique capabilities of the ms/ms analysis with examples taken from our work on coal liquefaction products. Figure 5 shows the positive ion chemical ionization (PCI) mass spectrum of the coal liquid in question (SRC II mid heavy distillate, total bottoms). This spectrum is actually the normalized sum of approximately 500 individual mass spectra taken while the SRC II was thermally vaporized from a solids probe into the source of a mass spectrometer, and represents the molecular weight profile of this distillate fraction. Since isobutane Cl gives to a first approximation only protonated molecular ions (and no fragment ions), the peaks represent the individual components in the SRC II arranged incrementally by molecular weight. 

Most of the ms/ms work on SRC samples has employed positive ion chemical ionization recently however, we have begun to explore the usefulness of negative ion chemical ionization (NCI). 

Analysis by positive ion chemical ionization of the permethylated ethylglycosides leads to spontaneous fragmentation of the molecular species. As shown in Figure 8.54, this fragmentation produces oxonium ions (resulting from the loss of ethanol) at m/z 219 (for non-deuterated hexoses). The oxonium ions then can lose a methanol molecule to yield a fragment 32 mass units lower (m/z 187 for the non-deuterated hexoses). 

Positive Ion Chemical Ionization Photo-Induced Dissociation Post-Source Decay Pyrolysis Mass Spectrometry Quadrupole device used in RF-only mode Quadrupole... 

Structural information about toxaphene components can be obtained by gas chromatography coupled to electron ionization mass spectrometry (GC/EI-MS), positive ion chemical ionization mass spectrometry (GC/PICI-MS) or negative ion chemical ionization MS(GC/NICI-MS). Mass separation is performed by low resolution quadrupole or high resolution magnetic field instruments, by ion trap systems (GC/IT-MS), or by tandem mass spectrometry (MS/MS) offering a broad spectrum of possibihties. 

This approach was pioneered by Hayward et al. [2] for the automated analysis of potential agricultural chemicals by means of eoluttm-bypass thermospray (TSP) MS-MS. The method was found to provide the required information in approximately 70% of the MS stmetural confirmations performed at the Agricultural Research Division of American Cyanamid. Subsequently, an automated routine MS eharaeterization of potential drug eompounds was reported by Tiller and Lane [3] at Glaxo. Both particle-beam (PBl) in positive-ion chemical ionization (Cl) mode and TSP interfaeing were investigated. The TSP system was found to be more robust, to require less maintenance, and to be easier to use. 

Figure 1.19 Mass spectra of acetaldehyde PFB-oxime (a), diacetyl mono PFB-oxime (b), acetoin PFB-oxime derivative (c), and o-chlorobenzaldehyde PFB-oxime (d) recorded in the GC/MS analysis of standard solution performed in positive ion chemical ionization mode using methane as reagent gas (reagent gas flow 1 mL/min ion source temperature 200 °C). Flamini et al., (2005) Monitoring of the principal carbonyl compounds involved in malolactic fermentation of wine by synthesis of 0-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine derivatives and solid-phase-microextraction positive-ion-chemical-ionization mass spectrometry analysis, Journal of Mass Spectrometry, 40, p. 1561. Copyright John Wiley Sons, Ltd. Reproduced with permission...

Flamini, R. and Dalla Vedova, A. (2004) Fast determination of the total free resver-atrol content in wine by direct-exposure-probe, positive-ion-chemical-ionization and collisional-induced-dissociation mass spectrometry (DEP/PICI-MS/MS), Rapid Commun. Mass Spectrom. 18(17), 1925-1931. 

Flamini, R., Dalla Vedova, A., Cancian, D., Panighel, A. and De Rosso, M. (2007) GC/MS-Positive Ion Chemical Ionization and MS/MS study of volatile benzene compounds in five different woods used in barrel-making, J. Mass Spectrom., 42, 641-646. 

In positive ion chemical ionization (PICI), the neutral analyte is most commonly ionized by proton transfer (Equation (4)) or adduct formation (Equations (5) and (6)). 

Prison, G.,Tedeschi, L, Maietti, S. and Ferrara, S.D. (1998). Determination of gamma-hydroxybutyric Acid (GHB) in plasma and urine by headspace solid-phase microextraction (SPME) and gas chromatography-positive ion chemical ionization-mass spectrometry. In Proceedings of the 1998 Joint Society of Forensic Toxicologists and the International Association of Forensic Toxicologists SOFT/TIAFT International Meeting, Spiehler, V. (Ed.), pp. 394 404. 

In field desorption (FD) and positive-ion chemical ionization (PICI) mass spectrometry of barbiturates, the molecular ion M+ and/or quasimolecular ion [M + 1]+ (41) are always observed.142-144 Fales et al.142 show that the... 

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