Pentane-extractable hydrocarbons

Figure 2. Total pentane-extractable hydrocarbons (fxg/g dry sediment)...

Picer and Picer [357] evaluated the application ofXAD-2, XAD-4, and Tenax macroreticular resins for concentrations of chlorinated insecticides and polychlorinated biphenyls in seawater prior to analysis by electron capture gas chromatography. The solvents that were used eluted not only the chlorinated hydrocarbons of interest but also other electron capture sensitive materials, so that eluates had to be purified. The eluates from the Tenax column were combined and the non-polar phase was separated from the polar phase in a glass separating funnel. Then the polar phase was extracted twice with n-pentane. The -pentane extract was dried over anhydrous sodium sulfate, concentrated to 1 ml and cleaned on an alumina column using a modification of the method described by Holden and Marsden. The eluates were placed on a silica gel column for the separation of PCBs from DDT, its metabolites, and dieldrin using a procedure described by Snyder and Reinert [359] and Picer and Abel [360]. 

Bridie et al. [27] have studied the solvent extraction of hydrocarbons and their oxidative products from oxidised and non-oxidised kerosine-water mixtures, using pentane, chloroform and carbon tetrachloride. Extracts are treated with Florasil to remove non-hydrocarbons before analysis by temperature programmed gas chromatography. From the results reported it is concluded that, although each of the solvents extracts the same amount of hydrocarbons, pentane extracts the smallest amount of non hydrocarbons. Florasil effectively removes non hydrocarbons from pentane extracts, but also removes 10-25% of aromatic hydrocarbons. However, as the other solvents are less susceptible than pentane to treatment with Florasil, pentane is considered by those workers to be the most suitable solvent for use in determining oil in water. 

For example the total pentane extracts of the web and cuticle from two European Agelenidae and Amaurobiidae comprised a complex mixture of fatty acids, alcohols and long-chain aliphatic hydrocarbons (Prouvost et al., 1999 Trabalon et al., 1996, 1997 Trabalon and Assi-Bessekon, 2008 Tables 16.1 and 16.2). The qualitative composition of cuticular extract obtained was similar to that reported for most insects and scorpions. Hydrocarbons in spiders form complex and varied mixtures with unsaturated hydrocarbons. In those species, the hydrocarbon fraction consists of n-, monomethyl- and... 

The yield and composition of the volatile fraction of the pentane extracts of leaves, stems and seeds of F. vulgare Mill, have been studied by Guillen and Manzanos (1996). The yield obtained from seeds was much higher than that obtained from leaves and stems. The volatile fraction of the pentane extract of the latter two has a higher concentration of terpene hydrocarbons and a smaller concentration of oxygenated terpene hydrocarbons than that of the seeds. Sesquiterpenes and the antioxidant vitamin E have been detected in the leaves and petroselinic acid in the seeds. Saturated aliphatic hydrocarbons with 25 or more carbon atoms have been found in all the plant parts. 

Deasphalting is a liquid-liquid separation operation that extracts the last of the easily convertible hydrocarbons from the vacuum residue. Solvents enipl ec) are light paraffins propane, butane, and pentane. The yimd In deasphalted oil increases with the molecular weight of the solvent, but its quality decreases. 5 uxct... 

Boylan and Tripp [76] determined hydrocarbons in seawater extracts of crude oil and crude oil fractions. Samples of polluted seawater and the aqueous phases of simulated samples (prepared by agitation of oil-kerosene mixtures and unpolluted seawater to various degrees) were extracted with pentane. Each extract was subjected to gas chromatography on a column (8 ft x 0.06 in) packed with 0.2% of Apiezon L on glass beads (80-100 mesh) and temperatures programmed from 60 °C to 220 °C at 4°C per minute. The components were identified by means of ultraviolet and mass spectra. Polar aromatic compounds in the samples were extracted with methanol-dichlorome-thane (1 3). 

Demex [Demetallization by extraction] A process for removing metal compounds from heavy petroleum fractions, after vacuum distillation, by solvent extraction and supercritical solvent recovery. The solvent is typically a mixture of octanes and pentanes. Developed jointly by UOP and the Institute Mexicano del Petroleo seven units were operating in 1988. Hydrocarbon Process., 1988, 67(9), 66. 

The direct high yield synthesis of oxaspiropentanes from almost any type of aldehyde or ketone represents a particularly useful transformation because of the high reactivity of such compounds. This approach proves to be exceptionally simple. The DMSO reaction mixture can be directly extracted with pentane or hexane, the hydrocarbon solvent removed and the product isolated by distillation or crystallization. Since diphenyl sulfide is the only by-product extracted with the oxaspiropentane, the mixture can normally be used for most further synthetic transformations. Table 2 summarizes some of the oxaspiropentanes prepared by this method. 

In a method described by Ryzhova et al. [30] for the determination of aliphatic hydrocarbons in wastewater sludges the hydrocarbons were extracted from sludge using a mixture of pentane and hexane. Metal salts... 

One particular method is designed to characterize Ce to C28+ petroleum hydrocarbons in soil as a series of aliphatic and aromatic carbon range fractions. The extraction methodology differs from other petroleum hydrocarbon methods because it uses n-pentane, not methylene chloride, as the extraction solvent. If methylene chloride is used as the extraction solvent, aliphatic and aromatic compounds cannot be separated. 

The silver nitrate solution is extracted as described above with three portions of -pentane to remove aVcyclooctene (Note 16). The aqueous silver nitrate solution is added slowly to 300 ml. of concentrated ammonium hydroxide containing cracked ice. The hydrocarbon that separates is extracted with 300 ml. of -pentane as described above and the pentane solution is dried over anhydrous magnesium sulfate and the pentane distilled through a 23 x 250 mm. column packed with glass beads. 

Distinctions between water-soluble fractions of mixed hydrocarbons may be made by using solvent extraction of the water-soluble base/neutral and acid fractions with methylene chloride (EPA 1991c Thomas and Delfino 1991a). This separation of base/neutral and acid fractions will permit the GC resolution of the type of water soluble hydrocarbons present in the aqueous phase. Hexane has also been used as a solvent (DellAcqua and Bush 1973), as has pentane (Coleman et al. 1984). 

Grapes release numerous hydrocarbons in the adjacent gas volume. We have found alkanes, alkenes, and aromatic hydrocarbons (II). Accordingly, we extracted the skin waxes of the grapes with n-pentane and investigated the extracts by using a combination GLC-mass spectrometer. The total amounts of the wax extracts contained about 0.5% paraffins, 89% of which were saturated hydrocarbons ranging from Ci3 to C3i. 

Heavy hydrocarbons were obtained by solvent extraction (4) of sediments, deasphalting with pentane, and separation by liquid chromatography (5) into saturate, aromatic, NSO-eluted, and asphaltene fractions. Saturate fractions were analyzed by gas-liquid chromatography (6) on these chromatograms (Figures 4 and 6) n-paraffins stand up as peaks above the naphthenic background. 

The nucleophilic nature of the alkanes is also shown by the influence of the acidity level on their solubility. Torek and co-workers90 have investigated the composition of the catalytic phase obtained when w-pentane or w-hexane is thoroughly mixed with HF-SbF5 in an autoclave under hydrogen pressure [Eq. (5.41)]. The total amount of hydrocarbon in the catalytic phase (dissolved ions and neutrals) was obtained by extraction with excess of methylcyclopentane. The amount of physically dissolved... 

Keymeulen et al. [49] determined various volatile chlorinated hydrocarbons in plant leaves by GC-MS. The method consists of solvent extraction with pentane followed by GC-MS. 

Hagenmaier et al. [59] have described a method for the quantitative gas chromatographic determination of volatile halogenated hydrocarbons in lake water samples. Sample enrichment is effected by liquid-liquid extraction with pentane, followed by separation on a capillary gas-liquid chromatographic column, with electron capture detection. A 1 25 pentane-water ratio was employed in conjunction with a standard solution of a reference compound (1-bromobutane) for estimating extraction... 

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