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Handbook of Size Exclusion Chromatography and Related ...

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Figure 5 Overlay<strong>of</strong>gelpermeationchromatogram(GPC)<strong>of</strong>commercialgrades<strong>of</strong>PVP<br />

using Shodex KB-80M mixed column <strong>and</strong> 20:80 (vol–vol) methanol–water with 0.1 M<br />

LiNO3.<br />

The weight-average molecular weights (relative to PEO st<strong>and</strong>ards) <strong>of</strong> the<br />

five commercial-grade PVP samples obtained from these three systems with the<br />

respective mobile phases are shown in Table 6. Also shown is a Polymer<br />

Laboratories polyethylene oxide st<strong>and</strong>ard <strong>of</strong> reported M w <strong>of</strong> 1,370,000 AMU.<br />

Good agreement in weight-average molecular weights were obtained for the low<strong>and</strong><br />

medium-molecular-weight grades PVP K-15, 30, <strong>and</strong> 60 samples among the<br />

threesystems.However,theShodexlinearcolumnyieldshighermolecularweight<br />

values for the high-molecular-weight grade PVP K-90 <strong>and</strong> 120 <strong>and</strong> the PEO<br />

st<strong>and</strong>ard than the Ultrahydrogel linear column. This indicates the Shodex linear<br />

column provides better separation at the high-molecular-weight end than the<br />

Ultrahydrogel linear column. The Ultrahydrogel column may also provide better<br />

separationatthehigh-molecular-weightendinthe20:80methanol–water mobile<br />

phase than inthe50:50methanol–water mobilephase;however,thedifference is<br />

small.<br />

© 2004 by Marcel Dekker, Inc.

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