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Handbook of Size Exclusion Chromatography and Related ...

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Selected applications are listed in Table 4. One <strong>of</strong> the most widely studied<br />

branched polymers is polyethylene. Rudin <strong>and</strong> co-workers (165,166) used SEC-<br />

LALLS to study branching in polyethylene in conjunction with intrinsic viscosity<br />

measurements. They found no appreciable difference between the two methods,<br />

indicating that there was little molecular weight polydispersity in each elution<br />

volume. They also compared SEC-LALLS results with static LALLS results <strong>and</strong><br />

found that the latter were significantly larger, possibly because <strong>of</strong> the poor<br />

refractometer signal at the high-molecular-weight end <strong>of</strong> the distribution. This is<br />

because <strong>of</strong> the molecular weight sensitivity <strong>of</strong> LS, which makes it especially<br />

sensitive to small amounts <strong>of</strong> highly branched material, or “microgel,” which are<br />

eitherfilteredoutbytheSECcolumnsorgivetoolowasignalintherefractometer.<br />

4.2.4 Biopolymers<br />

Studies relating to the use <strong>of</strong> SEC-LS for several classes <strong>of</strong> polysaccharides <strong>and</strong><br />

cellulosics are listed in Table 3. In addition, Dean <strong>and</strong> Rollings (184) studied<br />

polysaccharide depolymerase activity in fermentation with SEC-LS. Agarose <strong>and</strong><br />

agarose-type polysaccharides, within a molecular weight range 80,000–<br />

140,000 g/mol, were also analyzed by SEC-LS (142).<br />

Table 5 lists selected applications <strong>of</strong> SEC-LS for biopolymers, mainly<br />

proteins. An earlier review <strong>of</strong> SEC-LS <strong>of</strong> biopolymers can be found in Ref. 209. It<br />

is <strong>of</strong> interest that there has been only one reported study on the use <strong>of</strong> SEC-LS for<br />

the analysis <strong>of</strong> nucleic acids (207).<br />

For protein characterization, SEC-LS has been used as an analytical<br />

procedure for determining the molecular weights <strong>of</strong> unknown samples <strong>and</strong> also<br />

Table 4 Characterization <strong>of</strong> Branched Polymers by SEC-LS: Selected Applications<br />

Macromolecule References<br />

Polyolefins 157–168<br />

Polyvinyl chloride 166<br />

Polyvinyl alcohol 169–172<br />

Polychloroprene 171<br />

Polystyrene 170,173,174<br />

Polyoctenamer 175<br />

Polybutadiene/polyisoprene 118,176–178<br />

Polysaccharides 179,180<br />

Dextran 127<br />

Polymethyl methacrylate 181<br />

Polyesters 182<br />

© 2004 by Marcel Dekker, Inc.

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