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Handbook of Size Exclusion Chromatography and Related ...

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Figure 7 Separation criteria in liquid chromatography. Entropy controlled separation<br />

(DS/k) according to differences in excluded volume (V e): size exclusion chromatography<br />

(SEC); mc; molecular conformation; CCD, chemical composition distr; lcb, long chain<br />

branched; scb, short chain branched; md, molecular dimension. Enthalpy controlled HPLCseparation<br />

(DH/kT) according to differences in interaction potential with the LC-matrix.<br />

principles should provide even more detailed information about ip, md, <strong>and</strong> mc<br />

contributions to obtained Ve fractions (Fig. 7).<br />

Because starch glucans at any time fill up volume in a very characteristic<br />

way, it is <strong>of</strong> utmost importance to underst<strong>and</strong> the controlling factors <strong>of</strong> how this is<br />

done <strong>and</strong> why it is done that way. By gaining such knowledge, diversity <strong>of</strong><br />

biological raw materials may be understood much better, <strong>and</strong> efficiency <strong>of</strong><br />

processing <strong>of</strong> such raw materials could be improved. The key characteristics that<br />

need to be determined are:<br />

. branching characteristics,<br />

. molecular weight distribution,<br />

. supermolecular dimensions <strong>and</strong> coherent segment dimensions.<br />

Several approaches, which include SEC, provide information with respect to<br />

these key characteristics. In particular, molecular weight <strong>of</strong> starch glucans may be<br />

determined in several ways:<br />

. Calibrated: applying reference glucan materials (e.g., dextrans) via peak<br />

position calibration or broad st<strong>and</strong>ard calibration;<br />

or absolutely by:<br />

. Light scattering (LS) combined with universal mass detection (SECmass/LS);<br />

or<br />

. Viscosity combined with universal mass detection (SEC-mass/visc).<br />

© 2004 by Marcel Dekker, Inc.

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