凝胶渗透色谱分析的精度和准确性

凝胶渗透色谱(GPC)是一种表征高聚物分子最和分子量分布等特征的物理化学方法。近年来,由于仪器的不断改进,包括高效填料的使用、多种检测器的联用及与计算机的联用、仪器操作和数据处理的自动化等,使其在高聚物领域中的应用范围不断扩大。当使用高灵敏度的浓度和分子量检测器时,GPC不但可以测定线性高聚物平均分子量及其分布,还可提供高聚物的支化情况、共聚物的分子量和化学组成等多种信息。但是不论用GPC进行哪一项研究,欲想得到定量数据,必然对GPC分析的精度和准确性提出要求。     

右旋糖酐水解液的凝胶透渗色谱分析

采用凝胶透渗色谱法分离右旋糖酐水解液并测定其重均分子量及分子量分布且进行比较。色谱条件包括以TSK-G3000 PW xL(7.8mm×30.0cm)为色谱柱,以0.71%Na2SO4溶液为流动相,流速为0.5 mL/min,柱温为35℃并用示差折光检测器。结果表明:该方法测出的重均分子量在允许的误差范围内,且简便,快速,可用于中间产品右旋糖酐水解液的质量控制。     

凝胶渗透色谱对二次催化溶胶-凝胶法制备硅胶微球过程的监控

采用凝胶渗透色谱法(GPC),通过对二次催化溶胶-凝胶法制备硅胶微球原料硅酸乙酯 40(TES40)、中间产物聚硅酸乙酯(PES)分子量的在线测定,实现了对反应过程的监控.采用Shodex KF-802凝胶色谱柱,以四氢呋喃为流动相,流速0.5 mL/min,柱温40 ℃,采用示差折光检测器检测.校正曲线为1gMw= ...     

利用凝胶渗透色谱示差-紫外检测器联用测定丁苯共聚物的组成分布

将凝胶渗透色谱(GPC)中的示差与紫外检测器联用,测定了无规共聚丁苯橡胶和SBS三元嵌段共聚物中各级分的组成变化.实验方法选择中对比了两种浓度参数的确定方法,发现通过改变注射量来实现浓度变化的方法优于使用系列浓度样品的方法.分别测定标准样品在紫外和示差检测器上信号产生的时间间隔可以确定两个检测器上信号的时间差.根据紫外-示差检测器联用可以看到SBR无规共聚物和三嵌段SBS共聚物样品中每一个级分中随着相对分子质量的变化,苯乙烯含量的变化.     

凝胶色谱与自动粘度计联用技术在高聚物研究中的应用

自动粘度计作为测定分子尺寸的手段与示差际光器联用于凝胶色谱检测器时,将大大扩大其应用范围,如测定粘度常数k、α与色谱柱分离和扩展同时校准,已成为测定聚合物长链支化的有力手段。联机的基本原理比较简单,如图1所示。     

凝胶渗透色谱仪试制成功

凝胶渗透色谱法是六十年代中期出现的一种快速的高聚物分子量分布的测定方法,它本质上是一种新型的柱色谱分离手段,可以根据溶液组份的分子尺寸大小的差别来进行分离,这就使原来某些较难解决的分离问题,得到了解决。最明显的一个例子就是高分子的分子量分布测定问题。高聚物的分子量分布是一个决定加工和使用性能的重要指标,过去没有一个实用的快速测定方法,凝胶色谱法的出现就提供了一个较满意的快速测定方法。由于凝胶色谱的独特性质,它已在石油化工、高分子工业、医药工业、生物化学等领域得到广泛的应用。随着我国石油化工的迅速发展,高分子工业的生     

关于GPC校准线准确程度的探讨

用凝胶渗透色谱法测定高聚物的分子量以及分子量分布,除了近年来的凝胶渗透色谱法和小角激光散射光度计联用技术以外,要想得到高聚物绝对的分子量和分子量分布数据,必须要制定分子量和淋出体积之间关系的校准线,才能用谱图计算出高聚物的各种平均分子量和分子量分布情况的数据,因此校准线的准确程度直接影响计算数据的准     

凝胶色谱-光散射联用法对壳聚糖及其产品的分子质量及分布的测量

采用国家基准物质氯化钠和甲苯校准了示差折光仪和增强光系统的仪器常数,用超纯水重量法校准了激光光散射仪到示差检测器之间的延时体积,用葡聚糖标准物质对各角度的光强进行归一化处理,研究了凝胶色谱-激光光散射联用方法中设备的校准和溯源。上述校准途径使仪器溯源到国际SI单位,从而确保了测量结果准确可靠。采用激光光散射仪测得壳聚糖及其产品术后防粘连隔离膜的光折射增量dn/dc值分别为0.118、0.092 mL/g,凝胶色谱-激光光散射联用方法测得壳聚糖及其产品术后防粘连隔离膜的重均分子质量分别为8.897×104、1.168×105g/mol;分子质量分布Mw/Mn分别为1.148±0.026和3.132±0.377。     

高效凝胶渗透色谱法测定聚异丁烯丁二酰亚胺无灰添加剂的组成及其分子量分布

聚异丁烯丁二酰亚胺无灰剂(以下简称“剂”)是润滑油主要的清净分散添加剂。国内外有关用凝胶渗透色谱法(GPC)研究剂的组成和分子量分布的文献报道尚不多见,仅有Hillman等应用GPC分离和渗析技术而得的“剂”和油分别作为标样,用外标法测定了“剂”的组成;Bartha等虽然应用GPC研究了“剂”中间产品和最终产品的分子量分布,但并没有研究组成与分子量分布之间的关系。 本工作采用μ-Styragel为固定相,四氢呋喃为流动相,示差折光检测器检测,从而测定了“剂”的组成及分子量分布,并以再循环分离技术考察了外加聚异丁烯(PIB)后的分离度,以及方法准确度及精密度等。     

水溶性聚酯的热降解动力学研究

水溶性聚酯的热降解动力学研究应宗荣李瑞霞吴大诚（四川联合大学轻纺学院成都６１００６５）关键词水溶性聚酯，热降解，动力学，活化能高聚物的热稳定性直接影响高聚物的应用和加工成型．高聚物在高温时易发生热降解，导致分子链断裂，分子量降低，性能劣化．研究...     

从特性粘数和GPC图谱获得重均分子量的新方法

本文提出了从未知样品的特性粘数和GPC图谱计算重均分子量的新方法,该方法可用于计算窄分布和宽分布的未知Mark-Houwink 常数的样品的重均分子量。用七个不同分子量和不同分布的实例验证了所提出的方法。结果与已知Mark-Houwink常数用普适校准法得到的结果一致。     

Universal calibration in GPC: A study of polystyrene,poly-α-methylstyrene,and polypropylene

The theoretical justification for using M[_η], or a similar quantity, as a universal calibration parameter in GPC is reviewed. The equation based on this parameter is applied to transform the primary calibration curve, obtained by means of polystyrene samples, into calibration curves for poly-α-methylstyrene, polypropylene, and linear polyethylene. The Mark–Houwink equations for these polymers, as they are used in the transformation, are discussed. The resulting GPC calibration curves are compared with molecular weights and peak elution volumes of fractionated poly-α-methylstyrene and polypropylene. The same comparison is made with samples of polypropylene and polyethylene having very broad molecular weight distributions. The agreement lies within experimental error.     

A NEW METHOD FOR ESTIMATION OF WEIGHT-AVERAGE MOLECULAR WEIGHT OF POLYMER FROM THE INTRINSIC VISCOSITY AND CHROMATOGRAM

A new method is proposed for estimation of weight-average molecular weight from the intrinsicviscosity and GPC chromatogram of a polymer sample for which Mark-Houwink coefficients are notknown. The method bases on an approximate relationship between GPC data and the intrinsicviscosity of the sample. Reliability of this method was tested by comparing with the universalcalibration method which requires known Mark-Houwink coefficients for seven samples havingdifferent molecular weight distributions. Results obtained by the new method are in excellent agree-ment with those by the universal calibration method.     

Gel permeation chromatography: On the shape of the calibration plot and molecular size separability

Data obtained from the calibration of GPC columns of different permeabilities with standard polystyrenes are reported. For single columns the logarithm molecular weight–elution volume plot is linear for approximately one and one-half decades in molecular weight. GPC separations are such that the separability of two samples of similar molecular weight improves as their mean molecular weight decreases. Because of this the analysis of high molecular weight polymers can best be accomplished on a series of columns in which each column has a high permeability limit. The elution volume for columns in series is shown to be the sum of the elution volumes of the individual columns. As higher molecular weights are eluted a pronounced tailing effect is observed.     

Ein verfahren zur eichung der gelchromatographie (GPC) mit präparaten beliebiger,bekannter molekulargewichtsverteilung

If, in GPC calibration, the mean elution volume (or centre of gravity volume) of the elution curves obtained with monomolecular samples is used, the mean elution volume of a polymolecular mixture is a weight-average. According to the calibration curve, a molecular weight average can be attributed to the mean elution volume. For the special case of a logarithmic-linear calibration curve, this is the geometric (weight) mean of the molecular weight. Thus one can perform broad-standard calibration of GPC without interference by column dispersion. The potential application for non-linear calibration curves is discussed. It is considered how calibration functions for the higher moments of the monomolecular elution curves could be determined and how universal calibration should be performed if the standards are polydisperse relative to hydrodynamic volume. Absolute determination of polydispersity becomes possible with an additional z-detector.     

Application of preparative gel-permeation chromatography to studies of low molecular weight carboxy-polybutadienes

Low molecular weight carboxy-polybutadiene liquid polymers are used as the binderfuel fraction in solid composite propellants. Analytical GPC determinations of low molecular weight materials (100 through 500 molecular weight range) were previously found to correlate significantly with final propellant properties. These low molecular weight materials are being characterized, and studies of their role in determining propellant physical properties are being conducted. Sufficient quantities of material in the 100–500 molecular weight range have been isolated by using preparative scale GPC to establish the chemical nature of these materials. Infrared and chemical analysis of fractions collected by using preparative GPC also has permitted the construction of functional group distribution profiles. In addition, narrow fractions isolated over the molecular weight range of the whole polymer were analyzed for average molecular weight by vapor pressure osmometry and have been used as calibration standards for analytical GPC.     

Universal calibration in GPC

The M[η]-elution volume calibration curve for gel-permeation chromatography (GPC) is based on the implicit assumption that the hydrodynamic volume of a solvated polymer species in the GPC columns is that which pertains at infinite dilution. This is not true of highly solvated high molecular weight fractions and results in apparent failure of this calibration in some instances. A model is presented to estimate hydrodynamic volumes of polymers at finite concentrations. The parameters required are polymer concentration, molecular weight, amorphous density, and the Mark-Houwink constants for the particular polymer–solvent combination. The calculated log (hydrodynamic volume)–elution volume relation provides a universal GPC calibration. The model accounts for the occasional shortcomings of the infinite dilution calibration and is essentially equivalent to it in noncritical cases. The use of the proposed calibration method is illustrated.     

高分子无扰尺寸的测定

本文用GPC-[η]联用仪测定高聚物分子的无扰尺寸,GPC将高聚物分成不同的级分,连用自动粘度计测其相应级分的粘度,并由GPC的标定线或普适标定线,得到各级分的分子量,再用使Mark-Houwink公式线性化的理论方程,图解外推到无扰状态,获得高聚物分子的无扰尺寸,对于聚苯乙烯和聚甲基丙烯酸甲酯,所得结果与直接法、习惯法一致。     

Determination of the width of a narrow molecular weight distribution by gel-permeation chromatography

A recycle gel-permeation chromatography (GPC) method for extrapolating to infinite resolution is proposed. From the GPC calibration curve, the extrapolated elution peak width volume can be converted into peak width in decades of molecular weight. For an essentially Gaussian distribution, the weight-average/number-average molecular weight ratio can be determined from a calculated conversion table.     

Determination of polymer branching with gel-permeation chromatography. I. Theory

The effect of long-and short-chain branching in polymer molecules on gel-permeation chromatographic (GPC) separation is discussed. The calculation of calibration curves for branched polymers is developed from the universal calibration technique based on the hydrodynamic volume concept and previously established relationships for the effect of branching on molecular dimensions. Typical calibration curves are shown for different branching models and degrees of branching. As branching increases, the curves are shown to converge. Methods of characterizing branching and molecular weight distributions of franctions and whole polymers from GPC and intrinsic viscosity data are presented.