Volatile Aromatics Research Articles

Metastable oxygen molecules in the troposphere.

The sources and steady-state concentration of singlet oxygen in the atmosphere are assessed in view of potential effects on the biosphere. Collision-induced absorption of sunlight by molecular oxygen in 1 atm of air produces O2 (a1 delta g) at a rate P = 1.6 x 10(9) cm-3 s-1 in bright sunlight. Less than 10% are added to this purely natural source by the photolysis of ozone, and by anthropogenic sensitizers (SO2, NO2, volatile aromatics). Collisional quenching of O2 (a1 delta g) by ground state oxygen establishes a steady-state concentration of ca. 1.7 x 10(8) cm-3. Reactions of singlet oxygen with other atmospheric pollutants are entirely negligible when compared with the concurrent reactions of ambient OH and O3. Potential effects of atmospheric singlet oxygen on the biosphere are limited by the deposition rate F less than or equal to 0.051 P, which depends on the production rate P of O2 (a1 delta g) in the air layer immediately above the flat surface.

Volatile flavour components of marula juice

The volatile aromatics of marula fruit picked in the Republic of South Africa were enriched by means of an established liquid-liquid extraction technique. GC and GC-MS analyses were employed to identify 60 components with Kovats Indices lower than 2,000 (CW20M).

Persistence of spilled oil in a Texas salt marsh

Analysis of a crude oil spilled at Harbor Island, Texas, USA, has shown rapid loss of low molecular weight alkanes and more volatile aromatics. Persistence of higher molecular weight n-alkanes (greater than C 22) and of the alkyl-substituted naphthalenes and phenanthrenes has been observed with concentrations decreasing slowly towards background levels. During the 24-month study, only slight differences in the carbon isotopic composition of the whole crude extract were noted when compared with the original oil. Changes in δ 13C of the order of 0·5ℵ were observed in the hexane and benzene eluates of a column chromatographic separation of the oil. This stability of the isotopic ratio is supportive of its use in the tracking of petroleum pollutants. Extrapolation of concentration decreases lead us to expect thatbaseline levels will not be achieved for at least another five years. Since this wasa small spill, and was weathered under harsh conditions, the potential long-term effect of a large spill in a salt marsh is emphasised.

Condensed phase aromatization during degradation of poly(vinyl chloride)

AbstractProton NMR results for partially degraded PVC show that aromatization accompanies dehydrochlorination in the condensed phase; subsequent fragmentation leads to loss of volatile aromatics.

Evaluation of surfactant-like effects of commonly used remedies for colds.

Volatile aromatics, eucalyptol, eucalyptus oil, camphor and menthol were spread on synthetic DPL films and pulmonary surfactants; the initial surface pressure of the surfactants was measured and the additional surface pressure increment recorded. Eucalyptol was allowed to be inhaled by rabbits and lung compliance was monitored. Under our experimental conditions the volatile aromatics exhibited surfactant-like effects, namely a decrease in surface tension between water and air and thus improved lung compliance values in vivo.

Priority pollutant analyses of industrial wastewaters using a microextraction approach

Abstract A methodology based on microextraction, i.e., a one‐step extraction in which the ratio of solvent:wastewater ranged from 1:40 to 1:100, is described for the analysis of priority pollutant volatile aromatics, phthalates, polynuclear aromatics, and phenols. The use of this method for extracting relatively non‐polar analytes is justified from both a theoretical and a practical viewpoint. Results obtained during an EPA verification analysis of a variety of industrial process waters and effluents are discussed with respect to precision, percent recoveries of analytes, specific analytical problems encountered, and the potential for extending this approach to other compound classes.

Volatile liquid hydrocarbons in the surface coastal waters of the Gulf of Mexico

Abstract A sampling and analysis procedure has been developed to determine quantitatively volatile liquid C 6 C 14 hydrocarbons, the most immediately toxic components of petroleum hydrocarbons, at the ng/l level characteristically found in marine waters. The method of analysis involves dynamic headspace sampling; continuous stripping of volatile hydrocarbons from heated seawater by an ultrapure inert gas, and trapping of volatile components on a solid polyphenyl ether adsorbent, Tenax-GC. The trapped components are subsequently desorbed from the Tenax-GC by heating to 250°C, with cryogenic (liquid nitrogen) trapping of the volatile hydrocarbons on a SE-30 pre-column. After the cryogenic trapping, the pre-column is then heated rapidly which ‘injects’ the trapped components onto a non-polar GC column for separation. The stripping system is uniquely designed in that the stripping of the volatiles is done in the sample bottle itself. Components are identified by means of GC-MS analyses and GC retention times. The reproducibility based on replicates is ±12%. The use of conventional oceanographic samplers is found to be unsuitable for liquid hydrocarbon sampling at the ng/l level. Distributions of liquid hydrocarbons were determined in coastal surface waters of the Gulf of Mexico. Total volatile n-alkane concentrations range from 7 ng/l to 50 ng/l, whereas total volatile aromatics (benzene, toluene, ethylbenzene and xylenes) range from 20 ng/l to 450 ng/l. At most sample stations, 80–90% of the total liquid hydrocarbons in surface water is aromatic. The contribution in seawater of these volatile hydrocarbons to the total solvent-extractable hydrocarbon budget is a few percent at most. A direct correlation exists between liquid hydrocarbon concentrations and C 1 C 5 hydrocarbon concentrations. Surface-water samples which show high liquid hydrocarbon concentrations (500 ng/l) are also extremely high in methane and ethane relative to open-ocean levels. Samples which are lowest in liquid hydrocarbons (30 ng/l) have concentrations of methane and ethane close to baseline or open-ocean concentrations.

Relationships of Oil Composition and Stratigraphy in Permian Basin of West Texas and New Mexico: ABSTRACT

Analyses of 313 crude oils from Cambrian to Cretaceous formations were studied to correlate the geologic occurrence of these oils with such characteristics as composition by hydrocarbon type (aromatics, naphthenes, and paraffins), content of gasoline and gas oil (determined by distillation and refractometric methods), distillate yields and residuum, sulphur and nitrogen contents, and cloud points. Five general categories, based on likenesses that may indicate a similar history, include most of the oils, but smaller groupings are also discussed. Table AVERAGE VALUES FOR CATEGORIES End_Page 2074------------------------------ Category I (Ellenburger and Simpson oils). The Simpson shale is considered as a likely source. Category II (a few Ellenburger and Simpson oils, Fusselman, Devonian, Mississippian, Pennsylvanian, Wolfcamp, a few Yeso oils). Probable sources are dark basinal shales of Woodford, Mississippian, Pennsylvanian, and Wolfcamp age, commonly associated with unconformities. Category III (Yeso and San Andres oils). These occur commonly now on the Northwest and Eastern shelves where sulphate content is high. Category IV (Spraberry, Delaware Mountain, some Wolfcamp, and Yeso oils). These are relatively unaltered oils, associated with or derived from basinal shales. Category V (San Andres, Grayburg, Queen, Seven Rivers, Yates, Rustler, Castile, Cretaceous oils). These oils appear altered; suggested reasons: reaction with sulphur, fresh-water leaching of volatile aromatics, microbial oxidation of wax. End_of_Article - Last_Page 2075------------