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Handbook of Size Exclusion Chromatography and Related ...

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23<br />

<strong>Size</strong> <strong>Exclusion</strong>/<br />

Hydrodynamic<br />

<strong>Chromatography</strong><br />

Shyhchang S. Huang<br />

Noveon, Inc.<br />

Brecksville, Ohio, U.S.A.<br />

1 INTRODUCTION<br />

<strong>Size</strong> exclusion chromatography (SEC) is currently the most widely used method<br />

for determining the molecular weight (MW) <strong>and</strong> molecular weight distributions<br />

(MWD) <strong>of</strong> polymers. What is less known is that during aSEC run another<br />

chromatographic separation mechanism, hydrodynamic chromatography (HdC),<br />

is also taking place. Figure 1shows polystyrene st<strong>and</strong>ards that were separated by<br />

these two mechanisms in asingle injection (1) using small-pore columns. The<br />

calibration curve for the chromatogram in Fig. 1is plotted in Fig. 2. It shows that<br />

st<strong>and</strong>ards larger than MW 5 10 5 are separated by HdC. Those smaller than<br />

5 10 4 are separated by SEC. In a larger pore-size column, the MW ranges<br />

separated by these two mechanisms overlap <strong>and</strong> it becomes difficult to distinguish<br />

from the calibration curve. HdC is currently used more for particle size<br />

distribution studies. It has also been investigated for MW studies (2,3). This<br />

chapter discusses the combination <strong>of</strong> these two mechanisms, whereby an analysis<br />

benefits from the separation abilities <strong>of</strong> both.<br />

© 2004 by Marcel Dekker, Inc.

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