Size exclusion chromatography of urea formaldehyde resins in dimethylformamide containing lithium chloride

A rapid, reproducible method for investigating the molecular mas distribution of urea formaldehyde resins by size exclusion chromatography has been developed. By using concentrated lithium chloride solution to prepare the sample, materials of high viscosity and high molecular mass can be easily dissolved. Chromatography in dimethyl formamide containing lithium chloride eliminates hydrogen bonding and ensures that realistic values for molecular mass averages are obtained.     

Size exclusion chromatography of cellulose nitrate

Summary There had been studied the calibration conditions on the system cellulose nitrate (sharp fractions) -THF--Styragel by comparing the viscosity averages of DP obtained from the elution curves of GPC with the corresponding viscosimetrically determined ones. Deriving the elution volumes from the integral elution curves and applying adjustment of the calibration by means of adequate iterations, a very good coincidence between DP_n(visc.) and DP_n(GPC) can be reached. The molecular weight distribution curves obtained by GPC and by precipitation fractionation agree within the limits of error of both methods. It appears, however, that if in the calibration only one kind of average value of the master samples had been involved, only the same type of average can be determined with satisfying exactness.     

Size exclusion chromatography of H-coal liquids on silica,polyvinylacetate and polystyrene columns

The physico-chemical properties of liquids derived from Kentucky coals have been examined using size exclusion chromatography. Three major types of column packing for s.e.c. have been used in the H-coal liquid analysis: inorganic silica particles commonly known as controlled pore glass, soft polyvinylacetate gel and a rigid polystyrene-divinylbenzene gel. Of these, the PVA column appears to be a general and versatile choice for routine s.e.c. analysis of coal-derived liquids.     

Characterization of branched polymers by size exclusion chromatography coupled with multiangle light scattering detector. I. Size exclusion chromatography elution behavior of branched polymers

The elution behavior of branched macromolecules during their separation by size exclusion chromatography (SEC) was studied. The elution behavior of branched polymers was investigated using samples of randomly branched polystyrene and star branched poly(benzyl methacrylate) of different levels of branching by means of a SEC chromatograph coupled with a multiangle light scattering detector. Abnormal SEC elution behavior was found to be typical for highly branched polymers. After a normal elution at small elution volumes the molar mass and root mean square radius of the eluting molecules increased with increasing elution volume. Several SEC experiments were carried out to find explanation for this effect and SEC separation was compared with the separation by thermal field flow fractionation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1588–1594, 2001     

Size exclusion chromatography (GPC) of cellulose nitrate using modified silicagel as stationary phase

Summary It had been studied the applicability of coated silicagel as stationary phase in size exclusion chromatography of cellulose nitrate. Sample concentration and injection volume had been standarized. The elution volumes corresponding to discrete molecular weights resulted in a high reproducibility provided the application of the standarized conditions. There does not occur any adsorption of the cellulose nitrate on the packing material. It could be confirmed that separation takes place by a size exclusion mechanism. Separation power of the system had been proved by comparing the distribution curves obtained by means of GPC and fractionation precipitation respectively on the same sample.     

Size exclusion chromatography with multiple detectors: Solution properties of linear chains of varying flexibility in tetrahydrofuran

Narrow molecular weight distribution polyisoprenes (PI), polybutadienes (PBD), poly(isobuty1enes) (PIB), poly(methylmethacry1ates) (PMMA), polystyrenes (PS), and poly(octadecy1 methacrylates) (PODMA) have been studied by size exclusion chromatography (SEC) in tetrahydrofuran (THF) with light scattering and viscometric detectors. The molecular weight (M) dependence of the intrinsic viscosity, [η], and radius of gyration, R_g, is reported for THF solutions of these polymers, in many instances for the first time. The availability of these data for a series of chains of varying flexibility allows a test of the universal calibration principle in SEC. Furthermore, an apparent dependence of the hydrodynamic parameter in good solvents, Φ, on chain stiffness is observed. All chains appear to exhibit hydrodynamic draining in THF. © 1996 John Wiley & Sons, Inc.     

Size exclusion behavior of polymers in amide solvents

Summary The size exclusion chromatography of neutral polymers and polymers containing ionic groups was investigated using N,N-dimethylacetamide (DMA) as mobile phase. As reported previously for N,N-dimethylformamide (DMF), acrylonitrile polymers containing charges, even those at terminal end groups, showed markedly small retention volumes and multimodal peaks by refractive index and 280 nm UV detectors. In DMA containing small amounts of LiBr the peaks of the ionic polymers were shifted to small retention volumes while neutral polymers with analogous chemical structures did not show the same behavior. As in the case of DMF the peculiarities observed in DMA were attributed to the formation of supramolecular structures by the interaction of the ionic groups in the polymer and the ionic species from DMA decomposition.     

Size exclusion behavior of polymers in amide solvents

Summary The abnormal behavior of acrylonitrile polymers shown by size exclusion chromatography (SEC) in N,N-dimethylformamide (DMF) was investigated by using model polymers having variable degrees of sulfonated moieties as electric charged groups. The unexpected small retention volume and very high UV absorption at 280 nm were observed in the case of the samples with ionic sulfonate groups even in very small amounts, as chain ends. The abnormal behavior was confirmed to be due to impurities of DMF decomposition which interact with charged groups in the polymers.     

Steric exclusion and partial exclusion by polymer incompatibility in gel permeation chromatography

The early elution of some polymers in gel permeation chromatography is represented by a network-limited mechanism involving a distribution coefficient, K_D, for steric exclusion and a distribution coefficient, K_P, for solute-gel interactions. Values of K_P below unity correspond to partial exclusion by polymer incompatibility with the gel. A thermodynamic treatment for K_P is presented, predicting that K_P decreases as molecular weight increases. Values of K_P determined from experimental results reported for separations of poly(vinyl acetate) and polyoxyethylene are in the direction predicted by the theoretical treatment for partial exclusion by polymer incompatibility.     

Solution properties of polyelectrolytes. II. Comparison of the effects of both polyion and eluent salt concentrations on the calibrations in aqueous exclusion chromatography

The elution behaviour of charged water-soluble polymers (sodium polystyrene sulphonate) in both salt-free and NaCl-containing aqueous mobile phases has been investigated by size-exclusion chromatography. A comparative analysis has been established between the results as a function of polyion and salt concentrations, which demonstrates that the chromatographic behaviour is similar in both cases. The variation of the slopes of the different concentration-dependent calibration curves is discussed in terms of polyelectrolyte conformational changes. Finally, a semi-empirical model has been developed to predict the dependence of the elution volume in either polyion or salt concentration, and its validity has been checked in a range from very dilute to moderate concentrations.     

Asphaltene analysis using size exclusion chromatography

A common technique used in coal liquefaction investigations is the asphaltene analysis, whereby products are separated into four major fractions (insolubles, preasphaltenes, asphaltenes and oils) by solvent extraction techniques. The fractions are defined by their solubility in organic solvents such as tetrahydrofuran, toluene and pentane. An instrumental method of analysis, using gel permeation liquid chromatography, was developed to reduce the problems with the conventional solvent separation. The technique relies upon the fact that the fractions differ in molecular size as well as solubility. The method uses one solvent (THF) and a single 100 Å microstyragel column to separate the three soluble fractions. The trends in the data obtained with the molecular size separation agree with the trends obtained by conventional solvent separations on the same samples.     

Elution and molecular weight parameters in exclusion chromatography

The mode of the chromatogram is inadequate for characterizing experimental elution curves, which are generally dissymmetrical. It is also dependent on axial diffusion. When the molecular weight distribution is defined either by the generalized exponential function or by the log-normal function, simulation of elution at finite resolution shows that the calibration curve at infinite resolution, independent of the flow rate of the carrier fluid, is approximated validly by correlating the first moment of the chromatogram (MEV) with the geometrical compound average $\text{(}\text{M}\text{?}{}_{\mathrm{n}}\text{M}\text{?}{}_{\mathrm{w}}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= M}{}_0$. The concentration effect seems to be controlled by a double extrapolation procedure defined by (1) treatment of the chromatograms using the calibration curve at zero concentration ($\text{In}\text{M}{}_0\text{versus}\text{lim}\text{c→o}\text{MEV}$), and (2) linear extrapolation to infinite dilution of the calculated molecular weight averages.     

Elution behaviour of diolmodified epoxides in size exclusion chromatography

The reaction of bisphenol A-diglycidyl ether (BADGE) with butane-1,4-diol (BD) in the presence of Mg(ClO₄)₂ leads to linear and branched oligomers. The formation ratio of these products depends on the reaction temperature. In experiments at 100°C, an epoxide consumption of up to 70% can be observed using HPLC. In this range all products show good solubility in THF, so that it is possible to follow the increasing molar mass by using SEC. A characteristic relation of the molar mass against the conversion rate is derived and SEC data of a branched product are discussed.     

Number-average molecular weight by size exclusion chromatography

It is now theoretically possible to obtain absolute accurate values of number-average molecular weight of complex polymers (e.g., branched polymers or copolymers) using size exclusion chromatography (SEC) with only a detector that measures the difference between the eluting polymer solution viscosity and the viscosity of the pure mobile phase (a differential viscometer [DV] detector). However, both precision and accuracy of these “DV M?_n” values are of concern. In this work, the precision of NBS 706 polystyrene was found to be two to three times worse for the DV M?_n than for the conventionally calculated M?_n. Also, regarding accuracy, the DV M?_n values were affected by the location of the universal calibration curve along the retention volume axis (a problem intimately associated with the problem of specifying the correct interdetector volume), the sensitivity of the DV detector to low molecular weights present in the sample, and axial dispersion. Each of these sources of error are examined in turn and two methods of calculating M?_n values are proposed. © 1994 John Wiley & Sons, Inc.     

Characterization of block copolymers by size exclusion chromatography

Summary Poly(ethyl methacrylate-b-deuterated methyl methacrylate), poly(styrene-b-methyl methacrylate), and poly(styrene-b-dimethylsiloxane)diblock copolymers have been characterized by means of size exclusion chromatography (GPC) apparatus fitted with four detectors in series, viz continuous viscometer, UV spectrophotometer, low angle light scattering photometer, and differential refractometer. The continuous measurements of the scattered light intensity, the limiting viscosity number, the concentration, and the chemical composition permits complete determination of the molecular characteristics of block copolymers.     

Chromatogram broadening of proteins and dextrans in size exclusion chromatography

The mechanisms governing the broadening of experimental chromatograms for proteins and paucidisperse dextrans were studied on TSK-G2000SW and TSK-G3000SW columns. Within the conditions studied, the chromatogram variance for all solutes increased linearly with increasing effluent flow rate. As predicted by current theories of the kinetics of size exclusion chromatography, this flow rate dependence is caused mainly by slow mass transport of the solute within the stationary phase of the column. Restricted diffusion within the stationary phase was dependent upon the ratio of solute molecular size to column pore radius and was similar for both proteins and dextrans. In comparison with results for monodisperse proteins, the broader chromatograms produced by dextrans were due to sample polydispersity and not to differences in solute column spreading. Corrections for column spreading on these columns are small for the determination of integral properties of polymers but may be significant when molecular weight distributions are of interest.     

Size exclusion chrormatographic studies on the urethane reaction in hydroxyl-terminated polymers

Size exclusion chromatography (SEC) has been used to study the influence of molecular weight on the reactivity of the hydroxyl group in free radically polymerised hydroxyl-terminated polybutadiene (HTPB). The HTPB prepolymer was converted into a UV-absorbing urethane derivative by reaction with phenylisocyanate and the degree of conversion was followed from the UV/DRI (Differential Refractive Index) signal of the derivative using dual detector SEC. Though the overall reaction levelled off at about 70% conversion at room temperature, the time taken by different molecular weight species to attain this level was different. The computed rate constants were larger for the higher molecular weights in a given sample. This is attributed to the polyfunctionality of the higher molecular weight species.     

体积排阻色谱法在药物蛋白检测中的应用

探讨了单克隆抗体A、抗体融合蛋白B两种蛋白在不同的体积排阻色谱柱上的分离效果及流动相条件对体积排阻色谱柱分离抗体融合蛋白B的影响。结果表明,分析抗体融合蛋白B纯度和相对分子质量需要正确选择体积排阻色谱柱和合适的流动相条件。