Use Of Gel Permeation Chromatography Research Articles

A Method of Self Calibration for Molecular Weight Distribution Determinations for Liquid Crystalline Polymers

Abstract A method of molecular weight calibration was devised for various substituted liquid crystalline polymers with substantial molecular weight repeat units. With the use of gel permeation chromatography, oligomer peak separation was achieved offering a method for self calibration for molecular weight distribution determinations. Employing an overlay of a low molecular weight polystyrene standard, a retention time marker was utilized as a source from which to mark an oligomer peak. The calibration plot produced using this technique showed much better correlation coefficients than that of the polystyrene calibration plot. In addition, molecular weight determinations made from the two techniques yielded two distinct molecular weight averages and distributions, indicating polystyrene to be a poor relative calibration method for the liquid crystalline polymers tested. The technique illustrates the utility of alternative calibration methods when samples show certain physical characteristics.

Radiation effects on the structure property of CA 80 for measuring personnel radiation doses

The effects of fast and albedo neutrons and alpha particles on the molecular fractions of cellulose nitrate type CA 80, as a tissue equivalent material have been measured through the use of gel permeation chromatography. The samples in the form of thin sheets were exposed to fission neutron fluences in the range 10 5–10 10 n/cm 2 and to different energies of alpha particles in the range 1–5 MeV. The effects of irradiation on paraffin phantom, application of lithium borate radiator to the sample and storage of irradiated specimens for different periods were measured. The results indicated that CA80 eluted in one main fraction. Irradiation with neutrons or alpha particles caused fragmentation of this fraction to smaller molecules. Small and acceptable fade of the induced changes by radiation in the polymer due to storage for more than one month were noticed. The possibility of applying this technique in radiation dosimetry was discussed.

The novolak calibration method applied to the GPC analysis of the UV photoresists

This paper first summarizes the influence of the molecular weight of the novolak-based photoresists on the different microlithographic steps: film deposition, soft bake, exposure, and hard bake. The second part deals with the use of gel permeation chromatography (GPC) for characterizing the photoresists. In order to convert elution curves into molecular weight distribution information, a calibration method is needed. The usual calibration techniques are poorly adapted to the analysis of photoresists. The proposed calibration method uses the first observable low molecular weight oligomers on the chromatogram as a standard. It is shown that experimental results are not dependent on the column set.

Separation and characterization of ?-caprolactone oligomers by gel permeation chromatography

It is shown that the combined use of gel permeation chromatography and the isocyanate method of determination of hydroxyl end groups extends the possibilities for studying complex oligomer mixtures of ɛ-caprolactone. Oligomer mixtures of ɛ-caprolactone obtained by (C6H5)3CSbCl6 and by (C6H5)3CK are investigated. At initiation by both the initiators — the cationic and the anionic one — a covalent bond between the initiator and the polymer chain is formed. In the case of the initiation by (C6H5)3CK intramolecular transesterification proceeds which results in cyclic oligomers. At initiation by (C6H5)3CSbCl6 linear oligomers are formed. It is assumed that the ɛ-caprolactone polymerization by (C6H5)3CSbCl6 proceeds by alkyl-oxygen bond scission.

Investigation of the surface structure of polymers by chromatographic methods : V. Use of gel permeation chromatography in the study of the porous structure of copolymers of glycidyl methacrylate

Gel permeation chromatography (GPC) was used in an inversion function to characterize the porous structure of macroporous copolymers. Using macroporous glycidyl methacrylate copolymers as an example, the relationships between the exclusion limit in GPC and the pore size and porosity of the sorbent, the distribution coefficient and the pore geometry and size, and the peak widening and morphology of the porous structure were established. Characteristic quantities are compared with results provided by other methods, especially electron microscopy, mercury porosimetry and nitrogen sorption. It was demonstrated that the porous structures of strongly cross-linked macroporous copolymers in the swollen and dry states differ.

Determination of the molecular weight of clinical dextran by gel permeation chromatography on TSK PW type columns

The need for dextran fractions with a narrow molecular-weight distribution for clinical use is well known. The definition of such material has significantly improved by the use of gel permeation chromatography (GPC) techniques. However, an internationally accepted standard method of analysis giving accurate and reproducible results in different laboratories has yet to be defined. This paper reviews the GPC packings that can be or have been used for determining the molecular weight distribution of dextran polymers. The application of GPC to the determination of the molecular weight of dextrans on TSK PW type columns is described and its accuracy and reproducibility are discussed. This material appears to meet the criteria required for a standard method.

Molecular weight distributions and size fractionations of H-coal liquids

This Paper deals with a comparative study on the use of gel permeation chromatography (g.p.c.) and vapour pressure osmometry (v.p.o.) to obtain molecular weight data for the hexane-soluble fractions of three H-coal liquids. The use of two types of column packing materials, polyvinylacetate and styrene-divinylbenzene copolymer gels, is described. A successful, preparative use of the polyvinylacetate gel to fractionate the hexane-soluble fraction of H-coal liquid, atmospheric still overhead (ASO), has been established. Molecular weight data obtained by v.p.o. for the benzene-soluble fraction and the pyridine-soluble fraction of the three H-coal liquids are reported. Solvent extraction has been utilized also to find the amount of oil, asphaltenes and asphaltols in the three H-coal liquids.

The use of gel permeation chromatography in investigating the degradation of cellulose during conservation bleaching

(1982). The use of gel permeation chromatography in investigating the degradation of cellulose during conservation bleaching. Studies in Conservation: Vol. 27, Preprints of the Contributions to the Washington Congress, 3-9 September 1982. Science and Technology in the Service of Conservation, pp. 85-88.

Metabolism of pentachloronitrobenzene- 14C (Quintozene) in fish

The use of gel permeation chromatography (GPC) and capillary gas chromatography (GC) with thermionic detection (NPD) is described as a routine methodology for the determination of organophosphorus pesticides in biota samples. Confirmatory analysis is done by capillary GC with mass spectrometry in the negative chemical ionization mode (NCI-MS). As an example, the use of GPC is described as trace-enrichment technique and clean-up to remove coextractive lipids in samples of mosquito fish Gambussia affinis collected during period of 1987–1989 in the rice crop fields of the Ebro Delta (Spain). Recoveries of dioxathion, fenitrothion, malathion, tetrachlorvinphos, azinphos-ethyl, ronnel and coumaphos varied between 60% and 80% depending on the compound.

Free radical polymerization kinetics - revisited

Abstract

A novel use of gel permeation chromatography in the determination of the composition of resin blends

A novel technique to determine the composition of two‐component resin blends using G.P.C. in conjunction with an iterative curve‐fitting computer program is described. The method is particularly suitable for calculating the composition of resin blends where chemical differences between the constituent resins are small, but where the individual components differ considerably in their molecular size distributions. In the case of resin blends where other analytical techniques are suitable for the determination of their composition, the G.P.C. approach affords an independent means to confirm these results. Good agreement between the actual and calculated compositions of two‐component blends was achieved in 14 out of 16 cases.

Enhancement of plasminogen activation and hydrolysis of purified fibrinogen and fibrin by dextran 70.

Dextran 70 significantly enhanced the rate of activation of plasminogen into plasmin by urokinase as evidenced by increments in amidolytic activity using substrate S-2251. Dextran 70 did not enhance the amidolytic activity of preformed plasmin or urokinase. The combined use of gel permeation chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) clearly demonstrated enhancement of purified fibrinogen and fibrin degradation by dextran. High molecular weight soluble fibrin complexes readily demonstrable in early digest mixtures of normal fibrin were virtually absent in digest mixtures of fibrin containing dextran. In addition, digest mixtures of fibrinogen or fibrin with dextran contained a significantly lower proportion of fragment X than did digest mixtures without dextran. In contrast, fibrinolysis and fibrinogenolysis induced by preformed plasmin was not influenced by dextran. Steric exclusion effects may explain these findings.

Quantitative Analysis of Mixed Polymer Systems by the Use of Gel Permeation Chromatography

Abstract The use of gel permeation chromatography for the quantitative analysis of composition in mixed polymer systems is presented. The advantages of this method in determining the compositions of conjugate phases in polymer 1-polymer 2-solvent systems is discussed with typical examples.

Mesophases Thermotropes de Poly(azomethlnes) A Chaines “Souples”

Abstract The thermotropic polymorphism of poly(azomethine) of general formula: p = 1,3,6, has been studied. The combined use of gel permeation chromatography, light scattering and viscosimetry enable the determination of the molecular weight of the samples and of the coefficients K and a of the Mark-Houwink viscosity law. We showed that, in dilute solution, the chains can be considered as flexible chains with excluded volume effect. By polarized light microscopy, the existence of thermo-tropic liquid-crystalline phases has been shown. The temperature of transition between the phases depends on the length of the aliphatic part. For example, for p = 6, after the crystalline phase, a smectic phase appears at 240°C and a nematic phase at 290°C. The nematic phase was proved by observing the threaded texture.

Preferential Solvation Study of Polyvinylpyrrolidone in Organic or Aqueous Mixed Solvents by GPC

Abstract This paper deals with the use of gel permeation chromatography for the determination of the preferential solvation of polyvinylpyr-rolidone in binary solvent mixtures. It is the first time that this technique is applied to preferential solvation in both organic and aqueous systems. With this rapid and accurate method, we determined values of the preferential solvation coefficient λ1, which are compared with those obtained by light scattering or dialysis equilibrium.

Use of Gel Permeation Chromatography in the Crime Laboratory

Abstract In this study, the ways in which GPC can be integrated into the crime laboratory's present analytical scheme for polymer products will be examined. Fingerprint chromatograms and chromatograms illustrating molecular weight determination of two types of commonly encountered physical evidence (fibers and tail light lense fragments) will be compared and discussed. The techniques involved in sample preparation and data interpretation will be given. Finally the potential advantages of GPC for use in the crime laboratory will be presented.

The Identification of Polychlorinated Terphenyls at Trace Levels in Human Adipose Tissue by Gas Chromatography/Mass Spectrometry

Pooled samples of human adipose extracts representative of the general population of the United States were examined by gas chromatography-mass spectrometry. The use of gel permeation chromatography for cleanup was found to offer a significant improvement in detection capability. In addition to previously documented organochlorine residues, numerous polychlorinated terphenyls and three additional components of technical chlordane were identified.

A rapid technique for the qualitative analysis of polymers and additives using stop-and-go g.p.c. and i.r.

The use of gel permeation chromatography operated in a stop-and-go mode combined with an infrared spectrometer detector permits rapid qualitative and quantitative analysis of additives in polymers. Additionally, the chemical composition of the polymer and its molecular weight and molecular weight distribution may be determined. The method does not require any preliminary separation steps.

Use of gel-permeation chromatography for the study of molecular weight distributions of thermo-plastic polyurethanes

Studies were made of MW and MWD of thermo-plastic polyurethanes (TPU) by gel permeation chromatography (GPC) using styro-gels in ethyl acetate. It was shown that the polydispersion of TPU is close to two, independent of the method of synthesis (in bulk or in solution) and the numerical average MW increases from 44,000 to 162,000 with a change of intrinsic viscosity from 0·36 to 1·04.

Fractionation of human parotid salivary proteins and the isolation of an histidine-rich acidic peptide which shows high affinity for hydroxyapatite surfaces

Anion exchange chromatography of the proteins from litre quantities of parotid saliva has been shown to be a particularly appropriate technique for obtaining substantial amounts of the more acidic macromolecular components present in this secretion. One specific component obtained by this means was further purified by the use of gel permeation chromatography using a recycling technique. This material was remarkable for its high content of histidine ( 190 residues 1000 ) and arginine ( 111 residues 1000 ) and for its elevated levels of the dicarboxylic amino acids ( 233 residues 1000 ), particularly aspartate ( 144 residues 1000 ). A value for its minimum molecular weight, 4520, calculated from the amino acid composition, was in good agreement with the value of 4510 obtained by analytical ultracentrifugation. Its isoelectric point was found to be 7.04 at 20 °C and carbohydrate was absent. Interest in this component arises as a consequence of its high affinity for hydroxyapatite and dental enamel surfaces, suggesting a possible role for this material in the early stages of the formation of the acquired enamel pellicle.