Preparative Gel Permeation Chromatography

Abstract

This Chapter is devoted to a particular mode of liquid chromatography: Gel Permeation Chromatography (G.P.C.). The field of G.P.C. mainly concerns polymers but can also be applied to small organic molecules where, as well see later, the technique is more closely related to classical liquid chromatography.     

Gel Permeation Chromatography of Polyelectrolytes

Abstract

The mechanisms are discussed which control the GPC elution of ionic solutes, both the polyelectrolytes and the low molecular salts. The processes involved are quite general and valid in organic and in aqueous solvents. The conclusion is that gel permeation chromatography is a powerfull method to characterize poly-electrolytes; and it is shown that the correct data on molecular weight distribution can be obtained when the ionic content in the eluent is larger than 5.10^?2 M and when the concentration injected is lower than the critical overlapping concentration. The interpretation of chromatograms can be performed using the universal calibration and a viscosimetric detector.     

Characterization of Polyethylene in Dibutoxymethane by High-Temperature Gel Permeation Chromatography with Triple Detection

This study presents the possibility of replacing the 1,2,4-trichlorobenzene (TCB) recommended by ASTM D 6474 for the analysis by gel permeation chromatography (GPC) of linear polyethylenes with dibutoxymethane (DBM, butylal), a halogen-free and less toxic solvent. The molecular weight distributions as well as the K and alpha parameters of the Mark-Houwink-Sakurada relationship were measured for polyethylene solutions in TCB and DBM, using a GPC system with triple detection (light scattering, differential refractive index, and viscometer). For commercial metallocene polyethylene resins typically used for film and packaging applications, the GPC method in DBM provided results comparable to those obtained in TCB.     

Determination of the Molecular Weight Distribution of Polyethylene Terephthalate by Gel Permeation Chromatography

Abstract

The determination of the molecular weight distribution of polyethylene terephthalate by GPC at room temperature is described. The solvent used is o-chlorophenol-chloroform (1:9) and pure chloroform is used as eluent. K and alpha of the Mark-Houwink equation of polyethylene terephthalate and of polystyrene in this solvent system were obtained. It was shown that the universal calibration can be applied.     

Gel Permeation Chromatography of Insulin

Abstract

Aquas gel permeation chromatography of insulin under denaturating conditions has been successfully performed on three different chromatographic supports. The separation pattern was identical to that obtained on soft gels (Sephadex, BioGel). The elution time was 10-20 min, recovery 98-100%.     

Atypic Gel Permeation Chromatography of Alcohols

Abstract

The elution behaviour of alcohols in the systems Bio Beads SX-8/dichloromethane and Sephadex LH-20/dichloromethane is investigated. On Bio Beads SX-8 the elution volumes are lower than expected for normal GPC behaviour, which is perhaps due to hydrogen bonding in solution. On Sephadex LH-20 adsorption takes place by means of hydrogen bonding, which can be used for very selective separations.     

High-Performance Gel Permeation Chromatography of Pectins

Abstract

A high-performance gel permeation chromatographic (GPC) method was developed to determine the molecular weight distribution of pectins. The chromatographic system consisted of a hydrophilic coated silica (SynChropak) as the packing and a pH 3.7 acetate buffer as the mobile phase. By use of this system, high-methoxy, low-methoxy, and amidated pectins could be analyzed within fifteen minutes. By determining partition coefficients (K_d) of pectins as a function of mobile phase composition, K_d values were found to be independent of ionic strength from 0.055 to 0.7 M using pH 3.7 acetate buffers, which was in agreement, with intrinsic viscosity data.     

Gel Permeation Chromatography of Polymers from Wood

Abstract

Polymers from wood, including cellulose via the methylol derivative, are soluble in dimethyl sulfoxide (DMSO). To perform gel permeation chromatography of these high polymers, a packing material was sought which combined adequate pore size with stability in DMSO. Contrary to recommended practice, it was discovered that gel permeation chromatography in DMSO can be performed on prepacked, high-performance columns of μ-Styragel without adverse effects from bead swelling. When using the methylol derivative of cellulose, it is necessary to freeze dry the reaction mixture to obtain a product which gives reproducible results from gel permeation chromatography.     

Recent Advances in Aqueous Gel Permeation Chromatography

Abstract

The recent literature on aqueous gel permeation chromatography is reviewed. The chromatography of charged and uncharged solutes has been considered. A major emphasis has been to document the newer types of column packings for use in aqueous systems and their typical applications.     

Solvation and Adsorption Effects in Gel Permeation Chromatography

Abstract

Saturated hydrocarbons are generally eluted according to molecular volumes in gel permeation chromatography (GPC). Other compounds, containing polar groups such as hydroxyl and carbonyl groups, deviate from the molecular volume/elution count relationship which is prepared using saturated hydrocarbons. The deviation is more or less observed regardless of the kinds of eluents. In this paper, this problem is investigated in detail with respect to infrared(IR) and proton magnetic resonance(NMR) spectra, and concentration dependences of peak heights and elution volumes in GPC. IR and NMR spectra reveal that alcohols, ketones and esters are strongly solvated by eluent molecules such as chloroform and tetrahydrofuran(THF). The solvation effect leads to faster elution for these compounds than expected for aliphatic hydrocarbons. On the other hand, the concentration dependences of elution counts and peak heights prove the adsorption of amines on polystyrene gel in chloroform. In fact, the elution rates of amines and polychlorides are retarded. In the case of aliphatic carboxylic acids, the elution mechanism is more complicated: association and adsorption effects would be overlapped.     

凝胶色谱与多角激光光散射联用研究聚氧化乙烯的扩展效应和链构象

采用凝胶色谱与多角激光光散射联用的方法,测定了一系列不同分子量的聚乙二醇(PEG)和聚氧化乙烯(PEO)在色谱柱中的扩展效应.扩展因子随PEG/PEO分子量的增加而增大,经扩展效应改正后得到了样品的准确分子量和分子量分布.同时建立了PEO的Z均回转半径Rgz与重均分子量Mw之间的单分散标度关系:Rgz=0.0272 Mw0.56,结果表明,长链PEO在水溶液中由于排除体积效应采取溶胀的无规线团构象.     

Adsorption Effects Observed in Gel Permeation Chromatography of Thiouracil

Abstract

In gel permeation chromatography (GPC), several compounds deviate from the molecular volume/elution count relationship which is prepared using satured hydrocarbons. In this paper, this problem is investigated in detail using thiouracil in aqueous solution as a model chromatographic adsorbate. The concentration dependences of elution counts and peak heights prove the adsorption of thiouracil on Sephadex G-25 when water is the solvent. Thus to investigate further the mechanisms of adsorption responsable for the chromatographic behaviour, thiouracil-Sephadex interac—tions were investigated by studying equilibrium adsorption. Isotherms of type IV of BDDT classification were found which are typically associated with a weak adsorption such as physisorption, on a porous solid. The effect of water structure perturbants, ionic strength and pH on this adsorption was consistent with the-hypothesis that with water as a solvent both aromatic adsorption and electrostatic interaction are the determinants of the affinity of this gel for a thiouracil compound. This may be particularly useful since results of equilibrium adsorption isotherms are frequently used to develop liquid chromatographic theories.     

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.     

以六氟异丙醇为溶剂的聚甲醛凝胶渗透色谱研究

研究了均聚和共聚甲醛在六氟异内醇中的凝胶渗透色谱（ＧＰＣ）。对共聚甲醛出现的缔合现象从主链结构作了解释，并找到了避免缔合的方法；对共聚甲醛ＧＰＣ淋洗曲线上的异常小峰从聚合机理角度进行了探讨，推测得到小峰所对应的物质。确定了以六氟异丙醇为溶剂的聚甲醛的凝胶色谱表征方法，并探索采用凝胶色谱－粘度计联用法得到分子量和分子量分布结果。     

凝胶渗透色谱用大孔硅胶的制备

采用ＮａＣｌ、ＬｉＣｌ～ＫＮＯ３３组分盐，通过一次焙烧扩孔，制备了孔径４×１０２～１×１０３ｎｍ的大孔硅胶，其孔容可达０．８ｍＬ／ｇ，孔度为０．６５以上。实验结果表明，可用于ＧＰＣ分离相对分子质量为１．５×１０７以下的聚丙烯酰胺。     

高温凝胶渗透色谱仪中气泡的排除

叙述了高温凝胶(渗透)色谱(GPC)的流动相中出现气泡时的现象,指出气泡的出现对仪器运行和样品测试的影响,以及排除气泡的方法和过程.对可能出现气泡的原因进行了分析,讨论了避免出现气泡现象需要注意的问题和采取的措施.     

凝胶渗透色谱技术在农药残留分析中的应用

综述了凝胶渗透色谱技术在食品农药残留分析中的应用、研究现状和存在的问题。测定的农药残留包含有机氯、有机磷、除虫菊酯和农药多残留等等。参考文献37篇。     

Calibration in High Temperature Gel Permeation Chromatography of Linear Polyethylenes

Abstract

The mathematical relationship between the gel permeation chromatography calibration curves of polystyrene and linear polyethylene has been determined in 1,2,4-trichlorobenzene at 130, 135 and 140°C. The experimentally determined relationship is in good agreement with that predicted from application of the principles of the universal calibration technique and published Mark-Houwink coefficients. Definition of this relationship enables the use of polystyrene as a secondary standard for gel permeation chromatographic determination of linear polyethylene molecular weight determinations.     

Analysis of Low Molecular Weight Polymers with Gel Permeation Chromatography

Intrinsic viscosities and gel permeation chromatography (GPC) elution times were determined in toluene on commercially available standards of polystyrene (PSTY) and polymethyl methacrylate (PMMA) having M_n in the range of 10³ to 10⁵ and 10⁴ to 10⁶, respectively. In addition, elution times were determined on the discrete GPC peaks of dimer, trimer, tetramer, etc. as seen in lower molecular weight PSTY and PMMA. Intrinsic viscosities of oligomers were estimated by extrapolation of the Mark-Houwind-Sakurada equations determined from our data, and the results were used to establish a universal calibration curve over a wide range of molecular weights. A similar approach was taken by using literature data for the intrinsic viscosities of PSTY and PMMA in tetra-hydrofuran. It was verified by proton NMR that the universal calibration curve so constructed is useful at M_n, values as low as 300. No correction was necessary for chain length dependence of the detector response.