Positive-ion chemical ionization mass

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). 

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

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. 

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...

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. 

GAS CHROMATOGRAPHY/POSITIVE-ION CHEMICAL IONIZATION MASS SPECTROMETRY... 

The chemical ionization process produces both positive (cations) and negative (anions) ions and thus, an alternative to positive-ion chemical ionization mass... 

Figure 1 Comparison of the electron ionization and positive-ion chemical ionization mass spectra of cocaine.

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