Analysis of chitosan by gel permeation chromatography

The effect of γ-radiation on the average molecular weight and the molecular-weight distribution of chitosan has been studied. The analysis of samples by gel permeation chromatography/size exclusion chromatography (GPC/SEC) has shown that the amount of high-molecular-weight fractions decreases and the amount of fractions containing low-molecular-weight chitosans (<50 kDa) increases with an increase in the radiation dose. The radiation-chemical yield of degradation is 11.0 particle/100 eV.     

Fractionation of polyethylene by gel permeation chromatography

The performance of the gel permeation chromatography (GPC) technique was studied with several commercial samples of linear high density polyethylene. A comparison of these data was made with those obtained from the elution column technique based on fractional dissolution. GPC gave reproducible fractionation data in the molecular weight range of 10³–10⁶. These data were obtained from two columns in series with nominal capacity of 1–10⁴ and 1–10⁶A. Polyethylene fractions of known molecular weights are required as calibration standards and for many commercial polyethylenes it is necessary to increase sensitivity at molecular weight higher than 10⁶.     

Separation of dextrans by gel permeation chromatography

The role of the intrinsic viscosity [η] as separation parameter in gel permeation chromatography (GPC) was studied for dextrans (from Leuconostoc mesenteroids B512) dissolved in water with deactivated silicagel (Porasil) as the column-filling material. For that purpose specific viscosities of dextran fractions eluted by GPC were measured as a function of the elution volume v. Provided that the elution volumes are corrected for zonal spreading, they are related to the intrinsic viscosities in an unambiguous way, probably reflecting a unique relationship between degree of branching and molecular weights. This was further investigated by developing an iteration method to prepare two calibration curves γ(v) and g(v), respectively, relating ln[\documentclass{article}\pagestyle{empty}\begin{document}$\left[ {\bar \eta } \right]$\end {document}] and InM (M is the molecular weight) to v. It required that the weight-average molecular weight M _w, the number-average molecular weight M _n, and the average intrinsic viscosity [\documentclass{article}\pagestyle{empty}\begin{document}$\left[ {\bar \eta } \right]$\end {document}] for a number of dextran samples (broad distributions) be previously known. The calibration curves found lead to consistent values of the above-mentioned averages. Moreover, they allow-establishment of the [\documentclass{article}\pagestyle{empty}\begin{document}$\left[ {\bar \eta } \right]$\end {document}]-M relationship over the range 5000 < M < 500,000.     

差减凝胶渗透色谱在产品浓度和品牌识别中的应用

差减凝胶渗透色谱(D-GPC)以已知的标准样品溶液作淋洗剂,样品溶液作进样试液,通过内部差减,快速准确地给出样品溶液与标准样品溶液各组分之间的差异。以聚乙二醇(PEG200)的浓度识别以及3种啤酒的品牌识别为例,通过比较常规GPC与D-GPC所得到的实验结果,说明D-GPC方法在啤酒质量控制和品牌识别等方面所具有的应用价值。     

Rapid analysis of membrane glycopeptides by gel permeation high-performance liquid chromatography

A rapid procedure for the analysis of glycopeptides has been developed using gel permeation high-performance liquid chromatography (HPLC). Glycopeptides derived by exhaustive pronase digestion of glycoproteins from radiolabeled human tumor and normal cell lines were chromatographed on DuPont GF-250 and GF-450 gel permeation columns in buffers containing non-ionic detergents. Effective separations of glycopeptides ranging in molecular mass from less than 600 daltons to more than 20,000 daltons, equivalent to the separation range of Sephadex G50 chromatography, were achieved in 7 min. The separations were dependent upon the use of an isocratic mobile phase, that contained a low-ionic-strength Tris buffer and Nonidet P-40 or Triton X-100. The mobilities of protein standards indicated the occurrence of a biphasic elution system, which favored the separation of species with molecular masses below 20,000 daltons. Glycopeptides isolated by this method could be applied directly to lectin or ion-exchange columns or could be digested with neuraminidase, endo H or other enzymes without further treatment. Removal of sialic acid from the glycopeptides caused a dramatic increase in retention time. Using this method, glycopeptides could be isolated rapidly and in high yield. The ease, speed and reproducibility of the separations and compatibility of the solvent systems with affinity or ion-exchange chromatography techniques make this gel permeation HPLC method an ideal initial step in the purification of glycopeptides.     

Analysis of proanthocyanidins by high-performance gel permeation chromatography

A high-performance gel permeation chromatography method was developed for the analysis of proanthocyanidins. The isocratic method consisted of two porous polystyrene-divinylbenzene columns (300 x 7.5 mm each, 5 microm, 100 and 500 A individual pore size) and a mobile phase consisting of N,N-dimethylformamide containing 1% (v/v) acetic acid, 5% (v/v) water and 0.15 M lithium chloride. The flow-rate was maintained at 1 ml/min, with a column temperature of 60 degrees C and with detection at 280 nm. The method was used to analyze proanthocyanidin fractions of increasing molecular mass and from different plant tissues. The average molecular mass of proanthocyanidin fractions as determined by acid catalysis in the presence of phloroglucinol, related well with their gel permeation chromatography column retention, yet significant differences in the retention properties between individual plant tissue isolates existed. Proanthocyanidin compositional differences between isolates may explain these differences. A second-order calibration curve was generated from fractionated grape seed proanthocyanidins and this curve was used to analyze grape seed proanthocyanidins isolated from grapes harvested at extremes of maturity.     

Separation and characterization of alkyl phenol formaldehyde resins demulsifier by adsorption chromatography, gel permeation chromatography, infrared spectrometry and nuclear magnetic resonance spectroscopy

This paper deals with the separation and characterization of alkyl phenol formaldehyde resins demulsifier by infrared spectrometry and nuclear magnetic resonance spectroscopy after separation of the different surfactants and low molecular additives by adsorption chromatography. Firstly, the types of surfactants are identified by methylene blue chloride-chloroform test method and the elemental analysis such as Ca, K, Mg, Na, P, S and N. Then, the different surfactants and low molecular components are separated by adsorption chromatography after parts of low molecular components are dried in an oven, and the molecular weight distribution is measured by gel permeation chromatography also. Finally, the separated surfactants are determined by Fourier transform infrared (FTIR) spectrometry and nuclear magnetic resonance (NMR) spectroscopy. The distortionless enhancement by polarization transfer (DEPT), H, C correlated spectroscopy (H, C-COSY), H, H correlated spectroscopy (H, H-COSY) and heteronuclear multiple-bond correlation (HMBC) spectroscopy are applied to determine the molecular structures.     

Characterization of polyurethane network chains by gel permeation chromatography

Starting materials, prepolymers, chain-extended oligomers, and polyurethane network chains were characterized by gel permeation chromatography in order to make clear the change of molecular distribution in the formation of polyurethane networks. The polyurethane networks were prepared from poly(oxypropylene)glycol (PPG 1000, M _n = 997, M _w/M _n = 1.04), 2,4-tolylene diisocyanate, and 1,4-butanediol by the prepolymer method. Polyurethane networks were degraded by the amine degradation method, by which allophanate groups as crosslinking sites were decomposed selectively. The prepolymer had four species. The polydispersity index of the prepolymer (M _w/M _n) was about 2, that is, the most probable distribution. The product of the chain-extending reaction of prepolymer with BD had five species. The molecular-weight distribution of this product was narrower than that of the prepolymer. The polydispersity of the interstitial chains between crosslinking sites was also narrower than that of the chain-extended product. The polyaddition mechanism in the formation of PPG–TDI–BD polyurethane networks was discussed.     

Clean-up of a pesticide-lanolin mixture by gel permeation chromatography

In this study, the efficiency of a clean-up method by gel permeation chromatography (GPC) for the separation of pesticides from lanolin is analyzed. The pesticides analyzed belong to two different families, organophosphorous and synthetic pyrethroids. Lanolin, a standard mixture of the pesticides, and a lanolin-pesticides mixture are injected in a GPC column. The recoveries and elution times from the GPC column of lanolin (by a gravimetric method) and pesticides (by gas chromatography-electron capture detector) are determined. From this column, a good separation of the lanolin-pesticides mixture is observed.     

Clean-up of plasma extracts by gel permeation chromatography during analysis of isosorbide nitrates by capillary gas chromatography.

This work describes how gel permeation chromatography (GPC) can be used for sample clean-up to reduce the fouling of the column in an automated on-column injector. The analytes were isolated from plasma together with the internal standard (isomannide dinitrate) by liquid-liquid extraction on Extrelut silica columns. The extracts were evaporated and reconstituted in tetrahydrofuran for separation of the analytes from non-volatile plasma components by GPC on a styrene-divinylbenzene column with 100 A pore size. A programmable autosampler with an additional three-way valve was used for injection and fraction collection. The molecular weight fraction between 100 and 700 a.m.u. was collected and transferred to the on-column autosampler for capillary gas chromatography on a 30-m column butt-connected to a 0.2-m pre-column. The pre-column was replaced after 50 sample injections. When the GPC purification was excluded from the work-up procedure a deposit of non-volatile components was formed at the injection zone of the pre-column which resulted in excessive peak-tailing after only five or six injections of plasma extract. The limit of determination was 0.2 ng/ml plasma for isosorbide dinitrate and 0.4 ng/ml for the mononitrates.     

Separation system for fractionation of polyacrylamide by gel permeation chromatography

Samples of polyacrylamide were prepared by radical polymerisation of monomer in aqueous solution. Fractions of polyacrylamide were produced by a fractional precipitation technique with methanol as non-solvent. Molecular weights of the polyacrylamides were determined by solution viscometry. Analytical gel permeation chromatography (GPC) of the polyacrylamide samples and fractions was performed with porous silicas having a chemically bonded aminopropyl phase and with an eluent consisting of formamide-water (1:5). The GPC retention results indicated the successful separation of polyacrylamides having molecular weights in the range 10⁴–10⁶. GPC of polyacrylamide with this separation system appeared to be dominated by a steric exclusion mechanism.     

Analysis of phenols in pyrolysis oils by gel permeation chromatography and multidimensional liquid chromatography

A simple method with minimal manual sample preparation was developed for the analysis of phenols in pyrolysis oils. Sample pre-treatment was done by gel permeation chromatography (GPC), where the high-molecular-mass lignins were separated from the phenols. Multidimensional liquid chromatography (LC-LC) was used in the analysis of the phenolic fraction. The pre-column was used for sample clean-up and pre-fractionation before introduction of the phenolic fraction to the analytical column. The repeatability and linearity of the total GPC and LC-LC methods were excellent. The results were in accordance with the reference method in which the sample pre-treatment was done by precipitating the lignins with water, and the phenols were extracted with toluene and analysed by GC-MS.     

Characterization of poly(D,L-lactic acid) by gel permeation chromatography

A number of samples of poly(D ,L -lactic acid) (PLA) with weight-average molecular weights M?_w in the range 15,000–350,000 were prepared by a ring-opening polymerization. The molecular weight distributions (MWDs) of these samples were determined by gel permeation chromatography (GPC). The method involves a universal calibration of the columns on the basis of polystyrene standards and a rapid iteration algorithm leading to the establishment of the Mark–Houwink relationship. In addition, osmometry and viscometry data are presented. The effect of hydrolytic degradation on the MWD of two PLA samples was studied by GPC.     

Separation of lithium from dead sea brines by gel permeation chromatography

Fractionation of Dead Sea brines by differential migration through a polyacrylamide gel is shown to be feasible. Lithium-enriched fractions obtained in the process contain no calcium or magnesium and only small quantities of sodium and potassium.