Teflon columns

The purity of the product was checked by vapor phase chromatography on a polyethylene glycol on Teflon column at 72°, 15 p.s.i., and a flow rate of 102 ml. of helium per minute. The sample appeared to be homogeneous, but, since the amine tails badly on the column, it is not possible to detect the presence of a small amount of water (less than 3%). 

Enzyme thermistors can be altered for measuring the activity of soluble enzymes. For this purpose, an inactive or empty Teflon column can be used as a reaction chamber. The sample and a buffer containing a suitable substrate in excess are passed through heat exchangers and thoroughly... 

Three compounds recovered from parfait columns were also previously tested for breakthrough from 5-mL Teflon beds (6). The capacity factors for these compounds and their recoveries from the Teflon bed of a parfait column showed a rough correlation. Phenanthrene, which was tested in the parfait column only in the presence of humate, was recovered essentially quantitatively from the 5-mL Teflon column and had a capacity factor of 368. About 15 of the caffeine applied to a parfait column in the absence of humate could be recovered from Teflon, and caffeine showed a capacity factor of 22. Only about 2 of the 2,4-dichlorophenol applied to parfait columns could be recovered on Teflon its capacity factor was 5.6. It may therefore be anticipated that compounds following the inverse correlation of solubility with capacity factor and having a capacity factor greater than about 20 should be detectably absorbed to the Teflon bed of a parfait column. Simply increasing the volume of the Teflon bed may also increase the absolute recovery of adsorbable solutes that have modest values of kFor this reason, a 150-mL bed of Teflon per 8 L of water may not be the ideal bed size a larger bed may be better. 

The contents of the — 140 C trap were purified further by another trap-to-lrap distillation through traps cooled to —95. — 116, and — 196 C. The contents of the — 95 C trap were found to be m-2,3-difluorooxirane(n.v-44), ci.s- and ow -3.5-difluoro-1,2,4-trioxolane(43), and small amountsofrK,m-l,2,3-trifluorocyclopropane and HC02H. As previously mentioned the ci.v.fM-cyclopropane is formed only on ozonolysis of the Z-alkene. The — 116 C trap contained Pw v-2.3-difluorooxirane (lrans-44), m.trcms-1,2,3-trifiuorocyclopropane. and small amounts of the cw-epoxide. The — 196 C trap contained mostly HCOF and small amounts of SiF4. The contents of each trap were further purified by preparative GC (17 ft x 0.25 in. Teflon column packed with 10% Halocarbon oil on 40 60 mesh Chromosorb T at 22 C). 

A Teflon-coated sampler (General Oceanics, 10-L Go-Flo) on a stainless steel hydrowire was used to obtain whole-water samples and samples for filtration from 16 points in the water column on each cruise. Samples were pressure filtered onboard ship, within a Class-100 laminar flow enclosure, in an all-Teflon column-filter holder (Savilex) through tared 0.4-pm track-etched filters (Nuclepore). Samples, both total P and total filtrable P, were acidified with high-purity HC1 (Ultrex) and immediately frozen. 

Methyl mercaptan, hydrogen sulphide FEF Teflon column, Poropak QS Sulphur specific flame ionisation 0.25ng H2S 0.5ng mesh [611]... 

These compounds were separated on a Teflon column packed with silica gel-NH2 (ODS Cj8 LiChrosorb NH2). The mobile phase was a solution of 25 mM KH2P04-25 mM K2HP04 (1 1, v/v, pH 6.8). Only 1 /xL samples were required for analysis. Detection was at 254 nm. The separations obtained with standards on this column are illustrated in Figure 9.96A... 

Volatile Acids and Ethanol. Volatile acids and ethanol were determined by gas chromatographic analysis using an Aerograph HiFi (model 550-B) equipped with a gold-plated flame ionization detector. Before analysis, samples were acidifled with 3% metaphosphoric acid and centrifuged. The injection volume was 3 juliters. The acids and ethanol were separated at 135 °C in a 9-ft Teflon column packed with Resoflex standard concentration P (Burrell Corp., Pittsburgh, Pa.). The column was packed by vibration and conditioned at 150°C. zero gas served as carrier gas at a flow rate of about 20 ml/minute. The H2 flow rate was maintained by a pressure of 34 psi and the O2 at about 400 ml/minute. 

Total (non-speciated) sulphur analysis may yield all the information needed or desired for some sampling programmes. When only a total sulphur measurement is required, the gas sample is passed through an empty Teflon column, by-passing the chromatographic column, and is sent directly into the detector (Tracor, 1973 Lovell, 1979). Total sulphur analyses can be very rapid, requiring less than 2 min. per analysis. 

Radiolysis and photolysis products were analyzed by injecting samples into an F M gas chromatograph provided with a flame ionization detector. A 1/4-inch o.d. Teflon column 2 ft. long, packed with Porapak Q, was used to separate the components from the column in a reasonably short time. In some cases fractions were trapped out from the helium stream at the column outlet and analyzed on a C.E.C. 21-103C mass spectrometer. Conventional high vacuum techniques were used in handling all gaseous samples and products. 

Fig. 34, Gas chromatographic separation of boron trichloride and dichloroborane on a 78 C Teflon column.

Fig, 70. Gas chromatogram of a fluorosilane mixture on a packed squalane on Teflon column. 

A comparison of LC methods for determination of cis-trans isomers of P-carotene was made on Vydac C18 201 TP and calcium hydroxide columns (186). The purity and relative distribution of P-carotene and its isomers in several commercially available products were evaluated by HPLC on several columns using a mobile phase of methanol/water (97 3) (187). Because carotenoids and chlorophylls are very sensitive to the nature of injection solvent, such as acetone, sample-solvent interaction may give rise to distorted and even false peaks (188). Because metal column frits may damage carotenoids. Teflon column frits should be used (189). Also artifacts may be produced on the column by reactions among the carotenoids, injection solvents, and mobile phase. Losses that occur during extraction and saponification can be reduced by use of suitable antioxidants (189). 

Dissolve the sample and 10 mg of beryllium metal in 10 ml 6 M hydrofluoric acid in a plastic bottle. Add 2 ml concentrated hydrofluoric acid. Add the solution to the top of a teflon column (i.d. 1.8 cm height 40 cm) filled with 30 g of Dowex 1X8 resin kept at room temperature. The resin was previously converted to the fluoride form by washing with 250 ml 6 M hydrofluoric acid. Elute with 6 M hydrofluoric acid at a 2.5 ml/min flow rate. After discarding the first 80 ml of eluate, collect the next 200 ml. Add dropwise 50 mg of yttrium nitrate hexahydrate dissolved in 10 ml of water while stirring with a magnetic stirrer. Continue stirring for 15 min. 

Catalyst (59) in a circulating fixed bed reactor served as an acyl transfer agent for reactions of acetyl chloride, isobutyl chloroformate, p-toluenesulfonyl chloride and isopropyl o-chlorophenyl phosphoryl chloride with nucleophiles such as alcohols, carboxylic acids, HF, thiols and amines. For example, excess benzoyl chloride in dichloromethane was circulated through a Teflon column containing 1-4 ml of polymer at 0 °C, followed by pure dichloromethane to remove excess benzoyl chloride. Circulation of p-nitrophenol through the column gave p-nitrophenyl thiobenzoate in quantitative yield as shown in Scheme 23. 

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