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Handbook of Size Exclusion Chromatography and Related ...

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slice(nearthetop<strong>of</strong>thepeakregion<strong>of</strong>Fig.12)forthemanydetectors(MALS),a<br />

triple detector, a dual angle detector, <strong>and</strong> a single (908) detector. Note the<br />

extremely small error bars associated with the data points fit.<br />

For apoor chromatography example, consider Fig. 14, which shows the<br />

excessRayleighratiosmeasuredfromasample<strong>of</strong>400kpullulanwhichresultedin<br />

verynoisysignalsatthelow-angledetectors.Figure15showstheresultantfitsata<br />

single slice (near the top <strong>of</strong> the peak region <strong>of</strong> Fig. 14) for the many detectors<br />

(MALS), atriple detector, adual angle detector, <strong>and</strong> asingle (908) detector. Note<br />

the extremely large error bars associated with the smaller angle data points. (We<br />

have seen similar fits in Fig. 3.) For this case <strong>of</strong> poor chromatography,the errors<br />

associated with the points add tremendous uncertainty to the two-angle results.<br />

Naturally with alight scattering detector situated at 908 only, for all but the<br />

smallest molecules, the results will be far from correct.<br />

Table 1summarizes the errors associated with the use <strong>of</strong> two, three, <strong>and</strong><br />

manydetectorsinthecalculation<strong>of</strong>molarmass<strong>and</strong>r.m.s.radiusunderconditions<br />

Figure 15 Fitstodatacollectedataslicenearthepeak<strong>of</strong>Fig.14forMALS,three-angle<br />

detector, dual angle detector, <strong>and</strong> single 908 detector.<br />

© 2004 by Marcel Dekker, Inc.

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