Composite size exclusion chromatography

The advent of size exclusion chromatography in the 1960 s provided an alternative to drying polymer-polymer-solvent samples to determine the equilibrium phase compositions. Size exclusion chromatography separates solvents from polymers and to a varying extent, polymers from polymers, based on the size of the molecules in solution. Ultraviolet spectrometry and refractive index detectors may be used to determine the concentrations of each of the polymers in each of the phases (Lloyd et al., 1980). 

An aqueous ethanol solution of acrylamide, 2,2 -methylenebisacrylamide as cross-linked agent and third acrylamide derivative, is dispersed in an n-alkane. Then three monomers are polymerized to spherical porous gels. The effect of the composition of the third monomer on the exclusion limits of the gel in size-exclusion chromatography has been investigated (82). 

It is basically a fractionation process that depends not only on molecular size, but also on chemical composition, stereo-configuration, branching, and crosslinking. For multicomponent systems, fractionation with different ion polymolecularity, chemical heterogeneity and sequence length distribution, solubility or elution fractionation is of primary importance. Therefore, gel permeation chromatography or size exclusion chromatography is used as an important tool for the characterization of PBAs. 

Advanced computational models are also developed to understand the formation of polymer microstructure and polymer morphology. Nonuniform compositional distribution in olefin copolymers can affect the chain solubility of highly crystalline polymers. When such compositional nonuniformity is present, hydrodynamic volume distribution measured by size exclusion chromatography does not match the exact copolymer molecular weight distribution. Therefore, it is necessary to calculate the hydrodynamic volume distribution from a copolymer kinetic model and to relate it to the copolymer molecular weight distribution. The finite molecular weight moment techniques that were developed for free radical homo- and co-polymerization processes can be used for such calculations [1,14,15]. 

Analysis of the MHR by high-performance size-exclusion chromatography (HPSEC) revealed three distinct populations to be present, which were isolated on a preparative scale. The composition of the populations differed mainly in the relative proportion of rhamnose, xylose and the amount of methyl esters and acetyl groups, although the general characteristics were rather similar (Table 2). However, degradation studies with RGase showed that, in contrast... 

Sugar composition (mol%) of MHR population A and fractions I-IV, obtained after Sephacryl S200 size-exclusion chromatography of the digest of MHR population A with RGase [39]. 

Thin-layer chromatography (75) and sodium dodecylsulfate-(poly)acrylamide gel electrophoresis (SDS-PAGE) are helpful for analyses of the lipid and protein composition, respectively. Size-exclusion chromatography allows estimation of the size distribution of the (proteo)liposomes and crude fractionation of the material as reviewed in Ref. 76. Accurate determinations of size distributions require analyses by static or dynamic... 

HE FIELD OF SIZE EXCLUSION CHROMATOGRAPHY (SEC) remains a viable and lively area of polymer characterization. Over the past several years, there has been considerable research activity in the area of SEC detection and data analysis in order to obtain more comprehensive information concerning the composition and molecular architecture of complex polymer systems. 

Figure 9. The effect of storage on protein and peptide composition in cooked ground beef stored in a refrigerator of 4 days (adapted from 7). Upper graph represents the size exclusion chromatography of acidic extracts of fresh, cooked, and cooked-stored beef. Lx)wer graph represents the reverse phase HPLC of peak II from the size exclusion chromatography.

Recovery, Purity and Amino Acid Composition of CMP. The elution profiles of the CMP powders obtained on size exclusion chromatography 23) are shown in Figure 6. Both CMP isolated from WPC and whey did not contain major... 

Size-exclusion chromatography (SEC) has been also used as complementary technique for characterizing changes in the composition of synthetic resins due to aging. In particular, it enables the determination of molecular weight distributions and the glass transition temperatures of resins. 

A wide variety of polymers have been analyzed by gel-permeation, or size-exclusion, chromatography (sec) to determine molecular weight distribution of the polymer and additives (86—92). Some work has been completed on expanding this technique to determine branching in certain polymers (93). Combinations of sec with pyrolysis—gc systems have been used to show that the relative composition of polystyrene or acrylonitrile—polystyrene copolymer is independent of molecule size (94). Improvements in gpc include smaller cross-linked polystyrene beads having narrow particle size distributions, which allow higher column efficiency and new families of porous hydrophilic gels to be used for aqueous gpc (95). 

High performance liquid chromatography (HPLC) of polymers is often thought to be synonymous with Size Exclusion Chromatography for separation by molar size. The present article deals with nonexclusion chromatography of polymers which enables separation by differences in the chemical structure and composition. 

Gel Permeation Chromatography (GPC), also known as Size Exclusion Chromatography (SEC), is a technique used to determine the average molecular weight distribution of a polymer sample. Using the appropriate detectors and analysis procedure it is also possible to obtain qualitative information on long chain branching or determine the composition distribution of copolymers. 

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