Autoxidation reactions of linoleic acid and tocopherol and of mixtures of the two have been monitored in the dry monolayer state while adsorbed on silica gel, by means of silica slurry spectrophotometry and oxygen uptake measurements. The UV absorbance of the products of linoleic acid alone is similar to that of previously characterized compounds, but that from tocopherol is not referable to any oxidation products known to the authors, regardless of whether the determination is made while adsorbed on silica or on the extracted products. Two compounds, designated A and B, having absorbance in ethanol at 2610–2670 and 3000 A, respectively, are the major products of tocopherol oxidation detectable by UV above 2200 A. They are a tocopheryl quinone without a hydroxyl group and an adduct of linoleic acid and oxidized tocopherol. The product distribution suggests that tocopherol may have a restricted migration in this system.
A calibrated TDLAS system was used to measure real-time ground level atmospheric NO levels near a busy suburban street. A sample atmospheric NO concentration trend diagram from midday is presented.
A method has been developed for visible and UV spectrophotometry of lipid monolayers after preadsorption on silica gel from solution in hydrocarbon solvents. Lipid-coated silica gel is made optically transparent in the desired spectral region by slurrying with an inert solvent mixture. Reproducible gels with nearly the same refractive index as the solvent are achieved by careful choice of mixed solvents and carefully timed settling periods. The gel is pipetted into a silica cuvette of 1 cm light path, and a 9 mm silica spacer bar is inserted between Teflon guide strips. Appropriate choice of solvent mixtures (mainly spectral grade cyclohexane and cyclooctane)permits quantitation of spectra down to 2250 Angstrom units, using a silica gel reference cell. Lipid elution from the monolayer into the solvent is usually less than 1% at the dry-mixing dilutions used. Spectra of known unsaturated carbonyl compounds adsorbed on silica show red shifts as great as 240 Angstrom units, while blue shifts as great as 100 Angstrom units are observed for tocopherol derivatives with an intact aromatic ring. Very small shifts are observed for polyenes. The extent and direction of the shifts are indicative of adsorption and its orientation and are useful in the preliminary determination of the class of an unknown compound. The silica slurry spectra of the important tocopherol oxidation products, the quinone, dimer and trimer, have been examined. Peak wavelength shifts are consistent with structures elsewhere proposed for these compounds.
NO and CO2 were measured simultaneously in exhaled breath from seven subjects 10 times over a period of 12 days. Exhaled CO2 was used to estimate NO values as laser characteristics fluctuate over time.
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