Systems magnetic resonance gases

Instmmental methods of analysis provide information about the specific composition and purity of the amines. QuaUtative information about the identity of the product (functional groups present) and quantitative analysis (amount of various components such as nitrile, amide, acid, and deterruination of unsaturation) can be obtained by infrared analysis. Gas chromatography (gc), with a Hquid phase of either Apiezon grease or Carbowax, and high performance Hquid chromatography (hplc), using siHca columns and solvent systems such as isooctane, methyl tert-huty ether, tetrahydrofuran, and methanol, are used for quantitative analysis of fatty amine mixtures. Nuclear magnetic resonance spectroscopy (nmr), both proton ( H) and carbon-13 ( C), which can be used for quaHtative and quantitative analysis, is an important method used to analyze fatty amines (8,81). 

The in situ monitoring of high temperature reactions by hpl29Xe magnetic resonance is still in its infancy. Although the previous work on gas phase dynamics in porous media has shown the feasibility of dynamic microscopy and M RI and the first in situ combustion NMR spectra have been collected, much more development remains to be done. To date, hpl29Xe NMR and MRI are currently the only techniques available to study gas dynamics in porous and opaque systems. 

A number of other laser spectroscopic techniques are of interest but space does not permit their discussion. A few specialized methods of detecting laser absorption worthy of mention include multiphoton ionization/mass spectrometry (28), which is extremely sensitive as well as mass selective for gas-phase systems optically detected magnetic resonance (29) laser intracavity absorption, which can be extremely sensitive and is applicable to gases or solutions (30) thermal blooming, which is also applicable to very weak absorbances in gases or liquids (31) and... 

A similar in vitro system used [%] A-9-DMHP mass spectra of incubation extracts were silylated and subjected to gas chromato-graphy/mass spectrometry. Strong evidence was accumulated that the major metabolite was U-hydroxy-DMHP. Overall recovery of the metabolite was only A.7% this low yield was insufficient for confirmatory analyses by other methods, such as nuclear magnetic resonance. The low recovery indicated to the investigators that DMHP and its metabolites are much more strongly bound to tissue components than are THC and its metabolites. Sixteen hours after injection of [ HjDMHP into mice, their brains were extracted. Gas chromatography of the extracts indicated retention times identical with those of synthetic 11-hydroxy-DMHP, which accounted for 90% of the radioactivity two... 

After 1 hour, the reaction is complete as monitored by gas chromatographic analysis on an Hewlett-Packard F M 5751 research chromatograph (1.85 m. x 0.313 cm. stainless-steel column of 10% Apiezon L on Chromosorb W AW/DMCS column temperature 250°). Thin-layer chromatography was found to be of little use in monitoring the reaction, as the Rf values for benzyl disulfide and benzyl sulfide are virtually identical for a variety of solvent systems tried. Proton magnetic resonance (benzene) shows that these two compounds have coincidental chemical shifts for the benzylic protons 8 3.4 (singlet). 

Male Fischer 344 rats were exposed by inhalation to 1% 2-chloro-1,1,1 -trifluoroethane for 2 h and then urine was collected for 24 h. Urinary metabolites identified by 19F nuclear magnetic resonance and gas chromatography/mass spectrometry were 2,2,2-trifluoroethyl glucuronide (16%), trifluoroacetic acid (14%), trifluoroacetaldehyde hydrate (26%), trifluoroacetaldehyde-urea adduct (40%) and inorganic fluoride (3%). A minor, unidentified metabolite was also detected. No covalent binding of fluorine-containing metabolites was observed in the liver and kidney from the exposed rats (Yin et al., 1995). In-vitro incubation of 2-chloro-1,1,1-trifluoroethane with rat liver microsomes and an NADPH-generating system has been shown to involve a dechlorination reaction (Salmon et al., 1981) that produced trifluoroacetaldehyde hydrate as the only metabolite (Yin et al., 1995). 

Tor reference. Positive identification can be made only by collecting the compound or transierring it as it elutes directly into another apparatus for analysis by other means, such as infrared or ultraviolet spectroscopy, mass spectrometry, or nuclear magnetic resonance. Commercially available apparatus is available which combines in a single unit both a gas chromatograph and an infrared, ultraviolet, or mass spectrometer for routine separation and identilicalion. The ancillary system may also be microprocessor-based, with an extensive memory for storing libraries of known infrared spectra or fragmentation patterns (in the case of mass spectrometers). Such systems allow microprocessor-controlled comparison and identilicalion of detected compounds. 

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