Effective Solvent System Research Articles

Wet development of polymer resists: A guide to solvent selection

AbstractThe criteria for selecting effective solvent systems for wet development of polymer resist materials are explored. Methods of estimating the polymer–solvent interactions are described, including the use of solubility parameters and the Flory–huggins interaction parameter. Methods of achieving θ‐conditions, which represent minimal solvent–precipitant mixtures, or the more novel approach of establishing cosolvent systems are described. The rate dissolution has also bee identified as a controlling parameter. Some optical and gravimetric methods for measuring dissolution rates for polymer films are outlined. Examples of the influence of these factors on the sensitivity and contrast of resists such as poly(methylmethacrylate) and poly(p‐methyl styrene‐stat‐chloromethyl styrene) are described.

Effective Solvent Systems for Separation of PTH-Amino Acids on Polyamide Sheet

Two dimensional thin layer chromatography on polyamide sheets is a useful method for identification of PTH-amino acids which have very close Rf-values. The solvent systems described here are particularly effective and have an edge over other solvent systems used for the separation of PTH-amino acids. The solvent systems provide a clear separation of all PTH-amono acids except lle / Leu in a relatively short time.

Thin-layer chromatographic separation and identification of some anions on copper sulphate impregnated silica gel layers

Thin-layer chromatographic behaviour of thirteen anions on plain silica gel and silica gel impregnated with copper sulphate solution has been investigated in aqueous-organic solvents containing acetone, some of which have achieved reliable and reproducible separations. The effect of copper sulphate concentration on the mobility of anions has been examined. The results obtained on plain silica gel have been compared with those obtained on copper sulphate impregnated layers. The impregnated layers dramatically change the selectivity and permit separations not possible on untreated silica. Aqueous sodium chloride-acetone (9∶1) and ammonium hydroxide-acetone (9∶1) were the most effective solvent systems for differential migration of anions. Better results in terms of clarity of detection and compactness of spots were found with HCOOH-acetone as compared to HCl-acetone.

Effect of Processing on the Content of Condensed Tannins in Rapeseed Meals

ABSTRACTThe condensed tannins of rapeseed meals produced by a two‐phase solvent extraction system were determined and compared with those of hexane‐extracted meals. Ground seeds were extracted with absolute methanol, 95% methanol, 10% (w/w) ammonia in methanol or 10% (w/w) ammonia in 95% methanol and hexane as a second phase. Tannins were extracted with 70% (v/v) aqueous acetone and assayed by the 0.5% vanillin methodology. Methanol alone extracted only 16% of the tannins; addition of 5% (v/v) water to methanol increased the efficiency of tannin extraction to 36%. The methanol‐ammonia‐water/hexane, however, was the most effective solvent system for the removal of tannins. The resultant meals contained from 4% to 33% of the condensed tannins which were originally present in rapeseed meals.

Some effective solvent systems for the rapid resolution of DNP-amino acids by thin-layer chromatography

The DNP-amino acids have been divided into two groups depending upon their chromatographic behaviour on silicagel thin layers in different solvent systems. Five solvent systems were developed for each of the two groups. The systems reported provide rapid resolution and can separate mixtures of six to eight DNP-amino acids. The systems provide separations of DNP-ala/pro, leu/phe and leu/ile which are difficult to separate by one-dimensional TLC.

Stability of poly-ε-caprolactam solutions in the organic solvent-lithium chloride system

Phase diagrams of concentrated poly-ε-caaprolactam (PA-6) solutions were studied in organic solvents containing LiCl additives. DMAA-LiCl are a more effective solvent system for aliphatic PA, compared with DMFA-LiCl. With an increase in LiCl content in the systems examined, solution viscosity and stability increases.

Effective solvent systems for separation and an improved detection method for amino acids by paper chromatoghraphy

Effective solvent systems for separation and an improved detection method for amino acids by paper chromatoghraphy

A simple and effective solvent system for elution of gonadotropins from concanavalin A affinity chromatography

Elution of gonadotropins and other glycoproteins from concanavalin A has been previously performed with competitive ligands such as α-methyl- d-mannopyranoside and α-methyl- d-glucopyranoside. In comparative studies we found that 1 m NH 4OH was a highly effective eluent solution and gave nearly complete recovery of gonadotropin as revealed by protein contents, immunological, and biological activities. Advantages of 1 m NH 4OH over the sugar derivatives are its low cost and volatile nature, and its ability to irreversibly inactivate concanavalin A. The use of this system permits further steps of purification to be performed directly or after lyophilization without dialysis.

SEPARATION OF FLAVOR COMPOUNDS FROM LIPIDS IN A MODEL SYSTEM BY MEANS OF MEMBRANE DIALYSIS

ABSTRACTThe separation of flavor compounds from lipids by membrane dialysis was studied using a model system consisting of 11 flavor compounds and corn oil dissolved in solvent. Several solvent systems and three perfluorosulfonic acid membranes were studied. The most effective solvent system was a mixture of 70% acetone and 30% pentane while the more effective membranes were ones with equivalent weights of 1200 and 1100g and thicknesses of 5 and 10 mils, respectively. Diffusion of the corn oil was less than 0.12% of the oil added. Calculation of permeances showed that diffusion decreased with increased molecular size. The diffusion of 2‐methoxypyrazine was hindered by either adsorption on to or reaction with the dialysis membrane. Reaction of the membrane with acetone (solvent) resulted in the formation of two artifacts.

An improved method for determination of air-borne polycyclic hydrocarbons

In a search for a more effective solvent system than those discovered up to 1971 for separating the polycyclic hydrocarbon mixtures occurring in high-temperature tars, modifications were made to one found in 1957. Whatman No. 4 paper impregnated with 10% liquid paraffin solution in petrol ether was used as stationary phase, and methanol saturated with liquid paraffin as ascending mobile phase. Chromatography at 18° for 6 hr on 45×45 cm sheets of paper gave a separation considerably better than that achieved originally. Special attention was paid to the fraction containing carcinogenic hydrocarbons. No column chromatography or other pretreatment was necessary. Owing to the better separation it is possible to determine further polycyclic hydrocarbons such as 1,2, 5, 6-dibenzoanthracene, 3, 4, 9, 10-dibenzopyrene, and 3, 4, 8, 9-di-benzopyrene. A spot-evaluating procedure and a pretreatment of air samples have been developed. This procedure permits analysis of imponderable air samples.

Carbon-13 magnetic resonance evaluation of polypeptide secondary structure and correlation with proton magnetic resonance studies.

With the use of appropriately chosen solvent pairs it is demonstrated that solvent dependence of peptide carbonyl carbon resonances can be correlated with polypeptide secondary structure. Solvent titrations show the peptide carbonyl which is intramolecularly hydrogen bonded to exhibit less chemical shift on going from a dimethylsulfoxide solution to a solution containing a solvent which is a good proton (or deuteron) donor. Effective solvent systems are dimethylsulfoxide paired with water, trifluoroethanol, or methanol. This approach is demonstrated with the pentapeptide of elastin.