Chloroform polyamide solvent

The molecular weights of the polyamides 45 and 55 were estimated as 25,000 and 67,000, respectively, on the basis of viscoslmetric measurements. Both polyamides displayed high optical activity they were highly hydrophilic and readily soluble in water and In organic solvents, including chloroform. Polyamide 55 was crystalline and yielded resistant films with a spherulitic texture (Scheme 13B). 

Fig. 196. Two-dimensional chromatogram on polyamide. Solvent 1 water-ethanol-butanone-acetylacetone (65 + 15 + 15 + 5) solvent 2 chloroform-methanol-butanone (60 + 26 + 14) (almost water-saturated).

The SEC mechanism demands only an isocratic (constant composition) solvent system with normally a single solvent. The most frequently used organic solvents are THF, chloroform, toluene, esters, ketones, DMF, etc. The key solvent parameters of interest in SEC are (i) solubility parameter (ii) refractive index (iii) UV/IR absorbance (iv) viscosity and (v) boiling point. Sample solutions are typically prepared at concentrations in the region of 0.5-5 mg mL-1. In general an injection volume of 25-100p,L per 300 x 7.5 mm column should be employed. For SEC operation with polyolefins chlorinated solvents (for detector sensitivity and increased boiling point) and elevated temperatures (110 to 150 °C) are required to dissolve olefin polymer. HFIP is the preferred solvent for SEC analysis of polyesters and polyamides. 

Polyamide is an especially useful adsorbent for the separation of phenols owing to the formation of hydrogen bonds between the phenolic compounds and the amide group of the polymer. Organic solvents of increasing polarity and aqueous-organic solutions have been used as eluents benzene, chloroform, ethylac-etate, water-methanol, water-acetone, water-acetic acid, and cyclohexane-acetic acid (93 7) mixtures. 

With a twofold to threefold excess in trifluoroacetic anhydride, reaction (1) is quantitative within 1 day at room temperature. The A-trifluoroacetylated polyamides (NTFA-PA) are soluble in many ordinary organic solvents, such as acetone, methylene chloride, chloroform, and tetrahydrofuran. In addition to the... 

Automated densitometry after TLC separation has been used for the determination of sulfacetamide, sulfamethazine and sulfathiazole in a compound preparation. The sulfonamide mixture is chromatographed on polyamide plates with dioxane-propanol-ethyl acetate (4 3 2), chloroform-methanol (16 3), chloroform-ethyl acetate-ethanol (2 2 1), and benzene- isobutanol-pyridine (4 3 0.5). Combinations of the first and third and second and third solvents are used for two-dimensional TLC of the compounds followed by determination by densitometry (92). 

A method for extraction of 2-cyclopentyl-cyclopentanone from polyamide 6.6 by MAE was developed to quantitate the amount of 2-cyclopentyl-cyclo-pentanone in the polyamide 6.6 samples [66] and to validate a MHS-SPME method for extraction of 2-cyclopentyl-cyclopentanone [67]. The method was optimized with respect to the type of solvent, extraction temperature, extraction time and sample-to-solvent ratio. Chloroform and methanol were evaluated as extracting solvents. After extraction at 90 °C for 30 min the highest recovery was achieved using methanol as a solvent. This is attributed to the better compatibility between polar polyamide 6.6 and polar methanol, which gives good swelHng of the polyamide 6.6 matrix and more effective extraction of analyte. The effect of extraction time on the recovery of 2-cyclopentyl-cyclopentanone was studied by extracting 1.0 g of... 

The solution coating technique was used in the preparation of the cellulose triacetate membrane discussed above. A solution of cellulose triacetate in chloroform was deposited on the porous support and the solvent was then evaporated leaving a thin film on the porous support. Thin film polymerization was used to prepare a polyfuran membrane barrier layer on polysulfone. In this case, the monomer furfuryl alcohol is polymerized in situ by adjustment of pH and temperature. This membrane proved to be highly susceptible to oxidizing agents and is of limited value. By far the most valuable technique in the formation of membrane barrier layers is interfacial polycondensation. In this method, a polymer is formed on the porous support surface at the interface of organic and aqueous phases by reaction of specific molecules dissolved in each phase. It is by this method that a number of polyamides and polyurea membrane barrier layers have been formed on polysulfone. Elements containing these membranes are available commercially. 

Number-average molecular weights around 30,000 were estimated for compounds 123 and 124, by gel-permeation chromatography and vis-cosimetry. Circular dichroism and 1H NMR data in chloroform suggested the presence of definite secondary structures in this solvent. Crystals of both 123 and 124 were obtained upon annealing, and their structures were studied by X-ray diffraction of powders and oriented fibers. Polyamide 123 seemed to adopt a PI triclinic structure as observed for... 

In comparison with the efforts made towards achieving soluble yet thermally stable polyamides, many more studies are still needed in the field of lyotropic polyamides if anisotropic solutions in common organic solvents such as THF, chloroform etc. are to be achieved. This remains an interesting area for the fabrication of polyamides. Water soluble polyamides on the other hand, remain intriguing for some specific applications such as additives in the paper industry as described by Vandenberg [69]. 

Typical solvents used in membrane production include N-methylpyrrolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, tetrahydrofuran, dioxane, dichloromethane, methyl acetate, ethyl acetate, and chloroform. They are used alone or in mixtures. These are used most frequently as non-solvents methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and t-butanol. Polymers involved include polysulfone, polyethersulfone, polyamide, polyimide, polyetherimide, polyolefins, polycarbonate, polyphenyleneoxide, poly(vinylidene fluoride), polyacrylonitrile, and cellulose and its derivatives. 

In practice, two-component solvent mixtures are employed as eluents and sample solvents inLC LC. One constituent of mixture supports elution of interactive polymer from the particular column, while another one induces its retention within column. To adjust polymer interactivity or to cope with the limited solubility of analyzed polymers, multicomponent solvents can be employed. Typical examples are mixtures of hexafluoropropanol with chloroform, which dissolve aromatic polyesters and some polyamides at ambient temperature. The sample solvents, eluents and barriers usually contain the same hquids but their composition is adjusted to fulfil their particular role Sample solvent must dissolve all its constituents and barrier must efficiently decelerate interactive macromolecules. Eluent serves either as a barrier in LC LCS, LC LCA and LC LCP or it promotes unhindered sample elution in LC LCD, LC LCU and LC LCI. 

Amino acid derivatives are best extracted from silica gel layers with methanol or with a mixture of methanol/ 25% NH3 (95 5) (7,10,17] or chloroform/methanol/ acetic acid (7 2 2) [77]. Peptides are extractable with acetone/water (1 1) [78], and amine derivatives are extractable with less polar solvents, e.g. ethyl acetate, benzene/acetic acid (99 1), benzene/triethylamine (95 5) [10,17], or with dioxane if, as well as fluorescence, radioactivity is to be measured by liquid scintillation counting [80]. Chloroform is suitable for the extraction of Dns-amino adds from polyamide sheets [40]. Exdt-ation and emission wavelengths are, if possible, adjusted to those of the individual Dns-deiivatives however, for almost every compound, exdtation can generally be achieved using the 365 nm mercury line. 

For two-dimensional chromatographic analysis of crude extracts, a small set of solvent systems has been selected 35) (Table 2). — The combinations of chloroform-methanol (95 5) (No. 4) with petroleum ether (b.p. 50—70°)-diethylether-methanol (40 60 1, twice) (No. 2) for less polar and of chloroform-methanol (9 1) (No. 5) and diethyl ether-dioxane-methanol (90 10 1) (No. 6) for more polar compounds have been used on silica gel. Good separation on commercially available polyamide-11 plates is achieved by petroleum ether (b.p. 50—70°)-ben-zene-butanone-methanol (45 35 10 10) (No. 7) and chloroform-buta-none-methanol (60 26 14) (39, 67). 

No solvent system resolves all the Dns-amino acids by ID chromatography. Also, 2D chromatography requires more than two runs for a complete resolution. The eluents most commonly used on polyamide layers are benzene-acetic acid (9 1), toluene-acetic acid (9 1), toluene-ethanol-acetic acid (17 1 2), water-formic acid (200 3), water-ethanol-ammonium hydroxide (17 2 1 and 14 15 1), ethylacetate-ethanol-ammonium hydroxide (20 5 1), n-heptane-n-buta-nol-acetic acid (3 3 1), chlorobenzene-acetic acid (9 1), and ethylacetate-acetic acid-methanol (20 1 1). On silica plates, acetone-isopropanol-25 % aqueous ammonia (9 7 1), chloroform-benzyl alcohol-ethyl acetate-acetic acid (6 4 5 0.2), chloroform-ethyl acetate-acetic acid (38 4 2.8 or 24 4 5), and dichloromethane-methanol-pro-pionic acid (21 3 2) are used. 

All DABTH-amino acids, except the Leu/Ile pair, can be separated by 2D chromatography on layers of polyamide, with water—acetic acid (2 1 v/v) and toluene— n-hexane-acetic acid (2 1 1 v/v/v) being solvents 1 and 2, respectively. Resolution of the DABTH-Leu/Dns-Ile pair on polyamide is possible with formic acid-ethanol (10 9 v/v) and on silica plates using chloroform-ethanol (100 3 v/v) as eluent. 

Protease was used as catalyst for polymer modification. Phenylalanine residues at the side chain of methacrylamide polymers were coupled with alanine (-butyl ester by Q -ch3nnotrypsin catalyst in water-chloroform solvent (71). Up to 35% peptide-bond formation was achieved for 7 days at room temperature. Polyamide synthesis was performed by cellulase-assisted polycondensation of chiral fiuorinated compoimd having carboxylic acid and amino groups (72). 

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