Molecular weight exclusion chromatography

A series of polyvinylpyridine standards of different molecular weight were analyzed by size-exclusion chromatography, yielding the following results. 

The molecular weight of SAN can be easily determined by either intrinsic viscosity or size-exclusion chromatography (sec). Relationships for both multipoint and single point viscosity methods are available (18,19). Two intrinsic viscosity and molecular weight relationships for azeotropic copolymers have been given (20,21) ... 

Hydroxyl number and molecular weight are normally determined by end-group analysis, by titration with acetic, phthaUc, or pyromellitic anhydride (264). Eor lower molecular weights (higher hydroxyl numbers), E- and C-nmr methods have been developed (265). Molecular weight deterrninations based on coUigative properties, eg, vapor-phase osmometry, or on molecular size, eg, size exclusion chromatography, are less useful because they do not measure the hydroxyl content. 

Size-exclusion chromatography (sec) easily and rapidly gives the complete molecular weight distribution and any desired average (6). Thus, it has become the technique of choice for determining molecular weights despite its relatively high initial cost. 

A novel cross-linked polystyrene-divinylbenzene copolymer has been produced from suspension polymerization with toluene as a diluent, having an average particle size of 2 to 50 /rm, with an exclusive molecular weight for the polystyrene standard from about 500 to 20,000 in gel-permeation chromatography. A process for preparing the PS-DVB copolymer by suspension polymerization in the presence of at least one free-radical polymerization initiator, such as 2,2 -azo-bis (2,4-dimethylvaleronitrile) with a half-life of about 2 to 60 min at 70°C, has been disclosed (78). 

The packing material for liquid chromatography is produced from styrene and divinylbenzene dissolved in 50 to 300% by weight of organic solvent to both monomers. The constitution of divinylbenzene in the monomer mixture is not less than 60% by weight. In gel-permeation chromatography, the exclusive molecular weight is not less than 1 X 10 in terms of standard polystyrene (79). 

Nonionic polysaccharides are one of the most simple substances to analyze by size exclusion chromatography because they seldom exhibit nonsize exclusion effects. Due to their wide molecular weight distribution, TSK-GEL PW columns are recommended for their analysis. 

Showa Denko K.K. started the Shodex HPLC business in 1973 by developing columns to determine the molecular weight distributions of polymers produced at its petrochemical plant. Since then, more than 600 items of columns have been developed to achieve various kinds of analyses. Among them are several series of columns that can be used for size exclusion chromatography. The abundant variety of columns is one of the important characteristics of Shodex. Any kind of analytical requirements can be satisfied by choosing the appropriate column supplied by Showa Denko. 

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