Pentane-methanol

The sensors were exposed to the following VOC n-pentane, methanol, benzene, triethylamine and acetic acid. 

The first use of supercritical fluid extraction (SFE) as an extraction technique was reported by Zosel [379]. Since then there have been many reports on the use of SFE to extract PCBs, phenols, PAHs, and other organic compounds from particulate matter, soils and sediments [362, 363, 380-389]. The attraction of SFE as an extraction technique is directly related to the unique properties of the supercritical fluid [390]. Supercritical fluids, which have been used, have low viscosities, high diffusion coefficients, and low flammabilities, which are all clearly superior to the organic solvents normally used. Carbon dioxide (C02, [362,363]) is the most common supercritical fluid used for SFE, since it is inexpensive and has a low critical temperature (31.3 °C) and pressure (72.2 bar). Other less commonly used fluids include nitrous oxide (N20), ammonia, fluoro-form, methane, pentane, methanol, ethanol, sulfur hexafluoride (SF6), and dichlorofluoromethane [362, 363, 391]. Most of these fluids are clearly less attractive as solvents in terms of toxicity or as environmentally benign chemicals. Commercial SFE systems are available, but some workers have also made inexpensive modular systems [390]. 

Oligomers prepared by radical polymerization of 2-vinylpyridine could be separated into tactic isomers on a silica column (250 x 4.6 dQ = 10 nm dP = 10 pm) with a gradient pentane/methanol (concave 10 to 40% in 30 min). The experiments were... 

Absorption spectra of 2-nitroanisole in supercritical C02, N20, Freon-13, ammonia and C02-methanol mixtures were obtained on a Cary model 1605 spectrophotometer operated in the dual beam mode. The gases used as supercritical solvents were of the highest purity available from the supplier (Matheson) and were further filtered prior to use. The mixed solvent system of C02-methanol was obtained from Scott Speciality Gases (15.4 wt% methanol), and other mixtures were made in the laboratory. Spectra of 2-nitroanisole in n-pentane, methanol, tetrahydrofuran and acetonitrile (Burdick A Jackson) were obtained using quartz cells with a 1-cm light path and with a pure solvent blank in the reference beam. Vapor phase and supercritical fluid spectra were obtained using an air reference. 

Since pentane and water exhibit immiscibility, we might consider decantation as the first step. If it worked, it would be an inexpensive one to carry out. But a rigorous three-phase equilibrium calculation predicts that, in the presence of acetone and methanol, the small water fraction in the feed does not form a second liquid phase so we reject this idea. The calculation also reveals that the feed mixture is almost at the azeotropic composition for the pentane/methanol binary pair. 

Fig. 3 CCC separation of fat-soluble vitamins by cross-axis CPC. Experimental conditions sample, (A) calciferol (3 mg) -1-vitamin A acetate (30 mg)-1-( )-oc-tocopherol acetate (40 mg) and (B) vitamin K3 (3 mg)-1-vitamin Ki (10 mg) solvent system, 2,2,4-trimethyl pentane/methanol (1 1) mobile phase, lower phase. For other experimental conditions, see Fig. 1 caption. SF = solvent front.

Quercia et al. used a microparticulate aluminium oxide column to separate the dihydroderivatives of some ergot alkaloids and pentane - methanol (98 2) or (97 3) as mobile phase. 

Wilsak, R.A. Campbell, S.W. Thodos, G. Vapor-liquid equilibrium measurements for the n-pentane-methanol system at 372.7, 397.7, and 422.6 K. Fluid Phase Equilib. 1987, 33, 157-171. 

Thomas, S. Bhethanabotla, V.R. Campbell, S.W. Total pressure measurements for n-pentane-methanol-2-butanol at 303.15 K. J. Chem. Eng. Data 1991, 36, 374-378. 

The determination of Ni, V, Fe, Co, Ni, Cr, Cu, As, Sb, Hg and Zn was carried out by neutron activation analysis. The separated fractions and crude oils were analyzed by the methods of Shah, et and Filby and Shah. To determine the contributions of the solvents used in separations to the trace element contents of the oil fractions, neutron activation analysis was used to measure the pentane, methanol and benzene trace element values. 

Benzene/ acetone Benzene/ methanol Benzene/ M-butanol Pentane/ methanol Tetrahydrofuran/ water Toluene/ ethanol Toluene/ M-butanol Toluene/ methanol... 

The drawback to this as a recovery method is that pentane carries very little methanol out of the system (pentane/methanol azeotrope, 8% w/w methanol) so that if the original mixture of methanol and THF is rich in methanol, a preliminary concentration is desirable to reach the THF/methanol azetrope (31% methanol). Since the relative volatility between methanol and the azeotrope is about 2.0, this should not be a difficult separation. 

Jentoft and Gouw Styrene oligomers, polyaromatic hydrocarbons, polyphenyl ethers Packed column 4m x O.D. 120-150 mesh Porasil C Pentane-methanol 95 5 UV Pressure program... 

Nieman and Rogers Styrene and siloxane oligomers Packed column Mixed mobile phase, e.g. pentane-methanol UV Pressure program... 

Klesper and Hartmann Styrene oligomers Packed column 300 cm X 0.2 cm LD. Porasil A Pentane-methanol 90 10 UV Separation of oligomers up to 4000 MM pressure program... 

Conaway et al. Styrene oligomers Packed column Porasil C, octadecyl derivatized Porasil C Pentane-methanol isopropanol- pentane UV Pressure program, downward temperature program... 

Schmitz et al. Vinyl carbazole and vinyl pyridine oligomers Packed column LiChrosorb Si 100 10 fim Lichrosorb Si 60 Pentane-1, 4-dioxane, nitrous oxide-methanol, pentane-methanol UV HPLC and SFC with gradient elution and pressure program... 

Crown thioethers occur as colorless crystalline solids, odor-free when pure. Their lack of odor results from their low vapor pressure of the common ligands only 9S3 sublimes readily. Most crown thioethers melt near 100 °C 12S4 is unusual in melting at over 200 °C. They dissolve readily in acetone, dimethylformamide, dimethylsulfoxide, ethylacetate, dichloromethane, chloroform, toluene, dioxane, and THF, to a lesser extent in diethyl ether, and to a still lesser extent in pentane, methanol, or water. They can be purified most easily by lecrystallization from, e.g. hexane/acetone or chloroform in the case of 9S3 vacuum sublimation provides an especially convenient means of purification. The purification of crown thioethers by high-performance liquid chromatography [70], and their analysis by mass spectrometry has been described [71]. 

Chromatographic fractionation CO2, n-pentane + methanol Styrene oligomer... 

Pentane/methanol (95 5) Supercritical fluid chromatogr., 220°C oligomers 1707... 

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