Capture Negative Chemical Ionization Mass Research Articles

Determination of isomeric polycyclic aromatic hydrocarbons in air particulate matter by high-resolution gas chromatography/negative ion chemical ionization mass spectrometry

High-resolution gas chromatography combined with electron capture negative ion chemical ionization (NICI) mass spectrometry looks to be a promising method for the detection of mutagenic and/or carcinogenic polycyclic aromatic hydrocarbons (PAH). When methane/nitrous oxide mixtures are used as reagent gas, (M - H)/sup -/, M/sup -/, (M + OH)/sup -/, (M - H + NO)/sup -/, and (M - H + N/sub 2/O)/sup -/ are formed in the ion source. Many isomeric PAH can be identified by significant differences in the abundance of these ions. NICI mass spectra and response factors obtained by both techniques are reported for 22 reference PAH. Some practical and instrumental aspects of the NICI mode are discussed. The method has been used for differentiation of isomeric benzofluoranthenes and benzofluorenes from methylfluoranthenes as well as for the determination of PAH in air particulate extracts. 2 figures, 3 tables.

Determination of guanfacine in human plasma by GC-MS with electron capture negative chemical ionization.

Electron capture negative chemical ionization mass spectrometry has been applied to the determination of guanfacine in biological samples. After derivatization with hexafluoroacetylacetone, gas-chromatography on fused silica capillary column and negative chemical ionization with methane, the compound is quantified using selected ion monitoring by comparing the intensity of the molecular anion at m/z = 417 with the intensity of the corresponding anion from the stable isotope labelled ( 13C- 15N 3-guanfacine) as internal standard. This method has been applied to the determination of the pharmacokinetic profile of guanfacine in man after a 2 mg oral dose.

Determination of nitrated polycyclic aromatic hydrocarbons by fused silica capillary gas chromatography/negative ion chemical ionization mass spectrometry

Gas chromotography/electron capture negative ion chemical ionization mass spectrometry is shown to be a very sensitive and selective determination method for nitrated polycyclic aromatic hydrocarbons (PAH). The detection limit was 1 pg injected to the GC column using single ion monitoring. The mass spectra are characterized by an intense molecular ion, the base peak in all spectra. The second most abundant ions were (M - 16)/sup -/ and (M - 30)/sup -/ for mono- and dinitro-PAH, respectively. The NO/sub 2//sup -/ ion (m/z 46) is observed in most spectra. There are few differences in the mass spectra of various isomeric compounds. The pressure and the temperature in the ion source had little influence on the mass spectra and sensitivity within the limits tested. The method is demonstrated on a synthetic mixture containing nitro-PAH, and on a toluene extract of a formerly commercial carbon black. The application to urban air particulate extracts is discussed. 4 figures, 4 tables.

The electron capture negative ion chemical ionization mass spectra of 2-(4′,6′-bistrifluoromethyl-2′-pyrimidinyl)-tetrahydroisoquinoline and 4-substituted analogues

Reaction of debrisoquine and 4-hydroxydebrisoquine with hexafluoroacetylacetone to form pyrimidinyltetrahydroisoquinolines is used as the basis for a gas chromatographic mass spectrometric assay for these two compounds. The electron impact, positive ion chemical ionization and electron capture negative ion chemical ionization mass spectra of these pyrimidinyltetrahydroisoquinolines are described and compared. The latter were found to give an intense response under electron capture negative ion chemical ionization conditions, thus allowing the development of a much more sensitive assay for debrisoquine and 4-hydroxydebrisoquine. Derivatives of the hydroxyl group in 2-(4′,6′-bistrifluoromethyl-2′-pyrimidinyl)-4-hydroxytetrahydroisoquinoline were synthesized with a view to further improving the electron capture negative ion chemical ionization response. The resulting mass spectra showed extensive fragmentation for perfluoroacyl esters and halogenated silyl ethers. Only dimethylsilyl and trimethylsilyl ethers gave similar spectral responses to the parent compound.

Hydroxypolychlorodibenzofurans in technical pentachlorophenol: Electron capture negative ion chemical ionization mass spectra of alkoxypolychlorodibenzofurans

A mixture of hydroxypolychlorodibenzofurans was isolated from technical pentachlorophenol. The alkyl ethers were prepared, and analyzed by fused silica capillary column gas chromatography electron capture negative ion chemical ionization mass spectrometry. The appearance of intense molecular ion peaks for the alkyl ethers apparently depends on the ring position of alkoxy substitution. Loss of chlorine atoms from the ring, followed by protonation of the resultant anion as the alkyl group is eliminated, is postulated on the basis of deuterium labeling experlments. Evidence is also presented for the presence of a hydroxyheptachlorodibenzodioxin in technical pentachlorophenol.

Determination of flurazepam in human plasma by gas chromatography-electron capture negative chemical ionization mass spectrometry.

Determination of flurazepam in human plasma by gas chromatography-electron capture negative chemical ionization mass spectrometry.

Identification of octachlorohydroxydiphenyl ethers in technical pentachlorophenol

Five hydroxyoctachlorodiphenyl ethers present in technical pentachlorophenol have been isolated and tentatively identified. Electron impact mass spectrometry and electron capture negative ion chemical ionization mass spectrometry were used to assist in the identification.