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Handbook of Size Exclusion Chromatography and Related ...

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Another example, shown in Fig. 5 (31), uses a viscosity detector system. The<br />

intrinsic viscosity decreases nearly linearly with retention volume across the<br />

main peak <strong>of</strong> the distribution, but it then drops distinctly near the lowmolecular-weight<br />

region <strong>of</strong> the chromatogram.<br />

Their conclusions on the SEC analysis <strong>of</strong> Z are that SEC/LALLS coupling<br />

is an effective characterization technique <strong>and</strong> the eluant should be free or chosen<br />

so that association is eliminated. Despite its mineral backbone, polyorganophosphazene<br />

also confirms the universality <strong>of</strong> the universal calibration concept,<br />

<strong>and</strong> examination <strong>of</strong> dilute solution viscosity behavior is a simple method <strong>of</strong><br />

screening a potential solution for SEC analysis.<br />

When using SEC to study rubber samples having the same unusual<br />

characteristics, properly selected dual or triple detectors yield much more<br />

comprehensive information on molecular characteristics. Otherwise, the use <strong>of</strong> a<br />

single detector in SEC for such samples may lead to erroneous conclusions.<br />

Commercially available detectors are LALLS, UV, infrared, <strong>and</strong> evaporative<br />

detector (ED) photometers with conventional RI detectors.<br />

Figure 5 Chromatograms <strong>of</strong> polybistrifluoroethoxyphosphazene using different<br />

detectors: (a) differential refractometer, (b) differential viscometer, <strong>and</strong> (c) intrinsic<br />

viscosity. Column: PLgel mixed bed. Mobile phase: acetone, cyclohexanone. Temperature:<br />

308C, 408C. (From Ref. 31.)<br />

© 2004 by Marcel Dekker, Inc.

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