Gas chromatographic distillation

Lube oil volatility is a measure of oil loss due to evaporation. Noack volatility measures the actual evaporative loss which is grade dependent, and a function of molecular composition and the efficiency of the distillation step. The volatility is generally lower for higher viscosity and higher VI base stocks. The gas chromatographic distillation (GCD) can be used to measure the front end of the boiling point curve and may be used as an indication of volatility, e.g. 10% off at 375°C. 

Gas Chromatographic Distillation D2887 GCDs may be for troubleshooting and predicting dewaxing performance... 

By custom, either the mid vapor temperature of the fraction or the mid-point of a gas chromatographic distillation of the fraction can be used for the mean average boiling point. In either case the method must be spedfied. 

Dynamic headspace GC/MS. The distillation of volatile and semivolatile compounds into a continuously flowing stream of carrier gas and into a device for trapping sample components. Contents of the trap are then introduced onto a gas chromatographic column. This is followed by mass spectrometric analysis of compounds eluting from the gas chromatograph. 

Acrolein is produced according to the specifications in Table 3. Acetaldehyde and acetone are the principal carbonyl impurities in freshly distilled acrolein. Acrolein dimer accumulates at 0.50% in 30 days at 25°C. Analysis by two gas chromatographic methods with thermal conductivity detectors can determine all significant impurities in acrolein. The analysis with Porapak Q, 175—300 p.m (50—80 mesh), programmed from 60 to 250°C at 10°C/min, does not separate acetone, propionaldehyde, and propylene oxide from acrolein. These separations are made with 20% Tergitol E-35 on 250—350 p.m (45—60 mesh) Chromosorb W, kept at 40°C until acrolein elutes and then programmed rapidly to 190°C to elute the remaining components. 

Concretes and absolutes, both obtained by total extraction of the plant material and not subject to any form of distillation other than solvent removal, are complex mixtures containing many chemical types over wide molecular weight ranges. In some cases, gas chromatographic analysis shows httle volatile material. Yet these products have powerful odors and contribute in important ways to the perfumes in which they are used. 

The aldehyde is separated from the lower aqueous layer as a colorless liquid and dried over 10 g. of anhydrous sodium sulfate. The drying agent is removed by filtration, and the product is distilled under reduced pressure using a Claisen distillation apparatus to give 92-94 g. (82-84%) of cyclohexanecarboxaldehyde, b.p. 52-63° (18 mm.), 1.4484 (Notes 10, 11). A purity of about 98% was established by gas chromatographic analysis (Note 12) the product is suitable for synthetic use without further purification (Note 13). 

The distilled product was determined by the checkers to be 85-90% pure (gas chromatographic analysis), the major impurity being... 

These products comprise whole crude oils, as well as bottom fractions of distilling units and (partly) converted materials. The common property of these products is the fact that they contain high-boiling material which is not amenable to gas chromatographic analysis. 

Gas chromatographic analysis showed this material to be at least 99% pure. The melting point of methyl 4-acetoxvbenzoate has been reported8 as 81-81.6°. In both their runs, the checkers obtained a distilled product which melted from 60° to 74°, resolidified at 74°, and then remolted at 78-79°. A sample recrystallized from hexane showed the same behavior. 

K. Mehlhose, Explosivstoffe 20 (3-4), 37-70 (1972) CA 78, 113513 (1973) Methods developed for detn of H20 in gun and rocket propints are column distn with n-PrOH and gas-chromatographic analysis of the distillate, corrected for continuous formation of water in decompn reactions and photometric methods, both based on the reaction of CoCl2 with water. Choice of the methods is based on a critical review (117 refs) of the usual methods of water detn by chemical and physical methods. A theoretical and exptl analysis of the new methods was made and their results compared with those of older methods. Application to mono-, di-, and tribasic and to double-base NC and poly (vinyl nitrate) propints is discussed... 

Pure (A)-1 -chloropropene was obtained by careful distillation of a mixture of (E)- and ( )-l -chloropropene (available from Columbia Organic Chemicals Company Inc.) using a Nester-Faust Teflon annular spinning band column [(Z)-l-chloropropene has b.p. 33° (A)-l-chloropropene has b.p. 37°]. Small quantities of powdered sodium bicarbonate and hydroquinone (1,4-benzenediol) placed in the distillation flask inhibit acid-catalyzed isomerization and polymerization. Gas chromatographic analysis of the material used in these experiments on a 4-m., 15% l,2,3-tris(2-cyanoethoxy)propane (TCEP) on Chromosorb P column, operated at room temperature, typically indicated that it had isomeric purity >99.9%. (A)- 1-Chloropropene is stable for several months at room temperature, but it should be stored in a cool place. 

One of the most frequent techniques for analyzing 1,4-dioxane is gas chromatography. Birkel et al. [319] proposed in 1979 a gas chromatographic method based on partial vacuum distillation of the sample, analyzing polysorbate 60 and 80 with sensitivity to the 0.5 ppm. Stafford et al. [320] proposed a direct injection GC method which meant an improvement to the Birkel s technique. Robinson and Ciurczak [321] described a direct GC method for the analysis of... 

The photocatalytic decomposition of water was carried out in a closed gas circulation system connected to a high-vacuum line. About 200 mg of a powdered catalyst was dispersed in pure distilled water and irradiated through a water filter with an Xe lamp operated at 400 W. Hydrogen and oxygen evolved in the gas phase were analyzed by a gas chromatograph which was directly connected to the reaction system. 

Chian et al. [69] point out that the Bellar and Iichtenberg [65] procedure of gas stripping followed by adsorption onto a suitable medium and subsequent thermal desorption onto a gas chromatograph-mass spectrometer is not very successful for trace determinations of volatile polar organic compounds such as the low molecular weight alcohols, ketones, and aldehydes. To achieve their required sensitivity of parts per billion, Chian et al. [69] carried out a simple distillation of several hundred ml of sample to produce a few ml of distillate. This achieved a concentration factor of between 10 and 100. The headspace gas injection-gas chromatographic method was then applied to the concentrate obtained by distillation. 

General Methods. Methanol used in kinetic runs was distilled from sodium methoxide or calcium hydride in a nitrogen atmosphere before use. Freshly distilled cyclohexanol was added to the methanol in the ratio 6.0 ml cyclohexanol/200 ml MeOH and was used as an internal standard for gas chromatographic (GC) analysis. Benzaldehyde was distilled under vacuum and stored under nitrogen at 5°. Other aldehydes (purchased from Aldrich) were also distilled before use. The corresponding alcohols (purchased from Aldrich) were distilled and used to prepare GC standards. All metal carbonyl cluster complexes were purchased from Strem Chemical Company and used as received. Tetrahydrofuran (THF) was distilled from sodium benzophenone under nitrogen before use. 

Kozloski RP. 1985. Simple method for concentrating volatiles in water for gas chromatographic analysis by vacuum distilation. J Chromotgr 346 408-412. 

Analysing volatile acids in aqueous systems, resulting mainly from the presence of water, have been reported [19]. The volatile acids high polarity as well as their tendency to associate and to be adsorbed firmly on the column require esterification prior to gas chromatographic determination. The presence of water interferes in esterification so that complex drying techniques and isolation of the acids by extraction, liquid solid chromatography, distillation, and even ion exchangers had to be used [20-23],... 

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