Handbook of Size Exclusion Chromatography and Related ...

Figure 7 Effectofbandbroadeningforapolymerwithpolydispersity2onthemeasured
moments of the molecular weight distribution by light scattering, where D2 is the slope of
log molecular weight and elution volume and sB is the peak variance caused by band
broadening. (From Ref. 37.)
Themeasuredpolydispersitycanbecorrectedforbandbroadeningusingthe
method of He et al. (38). For columns with alinear calibration curve in logMW
with slope D2, the true polydispersity is given by
where D0 2
detector and s2 T
M w
¼e
M n TRUE
D2D0 2 (1 D0 2 =D2)s2 T
M w
M n SEC-LALLS
isthe experimental calibration curve measured by the light-scattering
isthe variance of the experimental concentration chromatogram.
Amore general form of the correction, which does not assume aGaussian peak
shape, has been developed by Lederer et al. (39) and Billiani and co-workers
(40–42). The same correction also applies to the intrinsic viscosity distribution,
the width of which is also underestimated.
In SEC-viscometry with universal calibration, as in conventional SEC, the
effect of band broadening is an apparent increase in polydispersity as the peak
broadens (Fig. 8). Although the true intrinsic viscosity is measured at each slice,
© 2004 by Marcel Dekker, Inc.
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