Chemical ionization mass spectrometry reagent gases

Figure 3.2 Piocesses occurring in chemical ionization mass spectrometry using methane as the reagent gas.

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

Gillis et al (Ref 79), using H2 reagent gas in a chemical ionization mass spectrometry system, suggest that the RDX mass spectrum can be rationalized by the following scheme ... 

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...

Hunt et al. [30a] utilized this mixed mode for the first time PPNICI (pulsed positive negative ion chemical ionization mass spectrometry) with quadrupolar instruments for the study of peptide sequences. The reagent gas chosen was a mixture of CH4 and CH3ONO. The resulting plasma was composed of CHj and CHjO (among others) and led to the positive [MH] and negative [M-H]" ions, respectively. 

Derivatization is also useful to detect volatile metabolites. Liu et al. [282] described a specific, rapid, and sensitive in situ derivatization solid-phase microextraction (SPME) method for determination of volatile trichloroethylene (TCE) metabolites, trichloroacetic acid (TCA), dichloroacetic acid (DCA), and trichloroethanol (TCOH), in rat blood. The metabolites were derivatized to their ethyl esters with acidic ethanol, extracted by SPME and then analyzed by gas chromatography/negative chemical ionization mass spectrometry (GC-NCI-MS). After validation, the method was successfully applied to investigate the toxicokinetic behavior of TCE metabolites following an oral dose of TCE. Some of the common derivatization reagents include acetyl chloride and TV-methyl-iV- ft-b u (y Idi methyl si I y I) tro (1 uoroacctam i nc (MTBSTFA) for phenols and aliphatic alcohols and amines, dansyl chloride and diazomethane for phenols, dansyl chloride for amines, acidic ethanol and diazomethane for carboxylic acids, and hydrazine for aldehydes. 

Pentafluorobenzyl hydroxylamine has been used as a derivatization reagent in the analysis of corticosteroids including prednisolone by gas chromatography-negative ion chemical ionization mass spectrometry (NCI). The resulting... 

F.a.b. mass spectrometry has been shown to be a useful tool for the identification of cello- and malto-ollgosaccharldes and their alditol reduction products. Permethylated slalo-oligosaccharldes liberated from parent gangllosides can be usefully examined by chemical ionization mass spectrometry with ammonia as reagent gas. Molecular weights are revealed by the MH and (M+NH ) ions and the... 

Gas chromatography-mass spectrometry (GC-MS) was performed with a Fin-nigan MAT (San Jose, CA) model 4021B quadrupole mass spectrometer interfaced to a Hewlett Packard 5890 GC equipped with an on-column injector. Mass spectra during GC-MS were obtained by chemical ionization with ammonia reagent gas at a source pressure of 0.3 torr. 

Mancel,V., Sellier,N., Lesage, D.,Fournier, F.,Tabet, I-C. (2004) Gas phase enantiomeric distinction of (R)- and (S)-aromatic hydroxy esters by negative ion chemical ionization mass spectrometry using a chiral reagent gas. Int. 7. Mass Spectrom.,237,185-195. 

Bicchi C, Caniato R, Tabacchi R, Tsoupras G (1989) Capillary gas-chrmnatography positive and negative-ion chemical ionization mass-spectrometry on pyrrolizidine alkaloids of Senecio inaequidens using ammonia and hydroxyl ions as the reagent speeies. J Nat Prod 52 32-41... 

Sieck, L.W. Determination of Molecular Weight Distribution of Aromatic Components in Petroleum Products by Chemical Ionization Mass Spectrometry With Chlorobenzene as Reagent Gas. Anal. Chem. 1983,55, 38-41. 

In chemical ionization-mass spectrometry (CI-MS), the sample molecules are combined with a stream of ionized reagent gas that is present in great excess relative to the sample. When the sample molecules collide with the preionized reagent gas, some of the sample molecules are ionized by various mechanisms, including proton transfer, electron nansfer, and adduct formation. Almost any readily available gas or highly volatile liquid can be used as a reagent gas for CI-MS. 

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