Showing papers on "Atmospheric-pressure chemical ionization published in 1974"

Identification of explosives by chemical ionization mass spectrometry using water as reagent

Abstract: Chemical ionization mass spectra of four explosive compounds have been obtained by using water as reagent gas. The compounds are 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane, 1,3,5-trinitor-1,3,5-triazacyclohexane, pentaerythritol tetranitrate, and an explosive which has been used in letter bombs, containing the two latter compounds and a plasticizer. The chemical ionization H2O mass spectra were recorded at an ion source temperature range of 170 to 225°C, a probe temperature range of 160 to 265°C and a reagent gas (H2O) pressure range of 0.07 to 0.10 Torr. Unlike in chemical ionization using methane or isobutane, chemical ionization H2O spectrum of these compounds provides a method for obtaining quasimolecular peaks. Adduct ion peaks like [M + H3O]+, [M + H5O2]+, [M + NO]+ and [M + NO2]+ are also observed in the chemical ionization H2O mass spectra of these compounds. Chemical ionization H2O mass spectra provide thus a better means of explosive identification.

Chemical ionization mass spectrometry. i‐Butane reactant gas modified by ethanolamine or ethylenediamine

Abstract: 1,2-Diaminoethane and 2-aminoethanol-1 were added to the isobutane plasma of a chemical ionization mass spectrometer. The resulting reactant gas mixture did not react with additives containing a single oxygen functional group. Addition reactions were observed with some additives containing multiple oxygen functions. Additives containing nitrogen functions were protonated by the reactant mixture. The relative proportion of protonation to addition depended on the ability of the additive to chelate the reactant ion and on the basicity of the additive. This use of 1,2-diaminoethane and 2-aminoethanol-1 provides a convenient method of varying the reactivity of the plasma in a chemical ionization source.

The use of solid probe chemical ionization mass spectrometry and gas chromatography-chemical ionization mass spectrometry in quantitation of drugs in biological fluids. Determination of tolbutamide and its metabolites in human plasma.

Abstract: Quantitative methods based on chemical ionization mass spectrometry are described for the determination of tolbutamide, a sulfonylurea, and its metabolites from human plasma. The sulfonylureas are extracted from the acidified plasma and then N-1 methylated with diazomethane. The methylated compounds can be subjected to gas chromatography where they are partially cleaved to the corresponding N-1 methylated sulfonamides. Alternatively, the methylated compounds can be introduced into the ion source by means of a solid sampler. The sulfonylureas upon evaporation from the solid sampler or the formed sulfonamide and the parent sulfonylurea upon elution from the gas chromatographic column are subjected to chemical ionization with methane as the reactant gas. The [M + H]+ ions formed are measured quantitatively with respect to the deuterium substituted internal standards. It is suggested that the technique of introducing biological extracts into the ion source via a solid probe may be applied for the quantification of compounds that are unstable under gas-liquid chromatographic conditions. Both the gas chromatographic and the non gas chromatographic methods provided excellent and comparable results. The plasma level-time profile of tolbutamide and its metabolites in a diabetic patient following the administration of 1.0 g tolbutamide intravenously is presented.

Characterization of dipeptides by electron impact and chemical ionization mass spectrometry.

Abstract: The components of mixtures of dipeptides can be identified from the electron ionization and chemical ionization mass spectra of their N-acetylacetonyl methyl ester derivatives without prior separation. The pyrolytic conversion of peptide trimethylanilinium salts to their methyl esters in the direct insertion probe of a mass spectrometer was found to be most suitable for the derivatization of dipeptides in mixtures.

The Use of a Solid Sampler in Chemical Ionization Mass Spectrometry for the Determination of Compounds Unstable Under Gas-Liquid Chromatographic Conditions-Analysis of Tolbutamide from Biological Fluid

Abstract: A simple method for the quantification of tolbutamide in biological fluids is presented. It is suggested that the method can be applied to some compounds that are unstable under gas liquid chromatographic conditions. The procedure is based upon the introduction of biological extracts into the ionization source of the mass spectrometer by means of a solid probe. Upon evaporation from the probe the compounds are subjected to high pressure chemical ionization with methane as a reactant gas. The abundant M + 1 ions that are formed are measured quantitatively with reference to deuterium substituted internal standard. Plasma concentrations of tolbutamide in rabbit following intravenous administration of 100 mg of tolbutamide is described.

Chemical ionization mass spectrometry—XIX:n-hexane andn-octane as reactants

Abstract: The suitability of n-hexane and n-octane as reactant gases in chemical ionization mass spectrometry has been investigated. The mass spectra of these substances have been investigated as a function of pressure up to 2·4 Torr for n-hexane and 1·7 Torr for n-octane. The major ion present in n-hexane at 0·8 Torr is [C6H13]+ (m/e 85) with a relative intensity of 0·65. In n-octane at 0·8 Torr the major ions are [C8H17]+ (m/e 113), [C6H13]+ (m/e 85) and [C5H11]+ (m/e 71). The relative intensities of these ions are 0·38, 0·12 and 0·19, respectively. These alkyl ions in both n-hexane and n-octane are thought to have tertiary structures. Rate constants for the rates of reaction of the primary ions in the two compounds have been determined. The n-hexane chemical ionization spectra of 26 compounds were determined. The spectra of polar compounds are dominated by proton transfer, whereas those of nonpolar compounds exhibit proton transfer and in addition often surprisingly large amounts of electron transfer. The n-octane chemical ionization spectra of 15 compounds were determined and the spectra in general are quite similar to those obtained with n-hexane. n-Hexane and n-octane can be used as reagents in analytical chemical ionization mass spectrometry, but except in certain specialized uses they would probably have no advantage over i-butane.

The field ionization spectra of some natural coumarins

Abstract: The field ionization and electron impact mass spectra of eleven coumarins have been compared. In the field ion spectra the molecular ions were the base peaks and structurally diagnostic fragment ions formed by direct cleavage were present, whereas the molecular ions were weak in the electron impact spectra and fragment ions formed by rearrangement were dominant. Crude coumarin mixtures obtained from natural sources have been successfully examined using field ionization and gas chromatography + field ionization mass spectrometry.

In situ mass analysis of particles by surface ionization mass spectrometry

Abstract: A qualitative study of the application of surface ionization and mass spectrometry to the in situ detection and constituent analysis of atmospheric particles was conducted. The technique consists of mass analysis of ions formed as a result of impingement of a stream of particles on a hot filament where, it is presumed, surface ionization takes place. Laboratory air particles containing K, Ca, and possibly hydrocarbons were detected. Other known particles such as Al2O3, Pb(NO3)2, and Cr2O3 were analyzed by detecting the respective metal atoms making up the particles. In some cases, mass numbers indicative of compounds making up the particles were detected showing surface ionization of particles sometimes leads to chemical analysis as well as to elemental analysis. Individual particles were detected, and it was shown that the technique is sensitive to Al2O3 particles with a mass of a few nanograms.