Handbook of Size Exclusion Chromatography and Related ...

Figure 2 SEC chromatogram of amixture of three polystyrene standards showing the
outputs of both a differential refractometer (top) and a viscometer (bottom).
where n0 ¼refractive index of the solvent, dn=dc ¼specific refractive index
increment of the solution, l0 ¼wavelength of the incident light in avacuum,
NA ¼Avogadro’snumber.
The particle-scattering function describes the angular variation of the
scattered light intensity and depends upon the polymer size and shape. At low
scattering angles it can be approximated by
2
1 4p 2 u
¼1þ sin
P(u) l 2
kRg 2 l z
3
where lis the wavelength of the incident light in the solution and kRg 2 l zis the
mean-square radius of gyration of the molecules in solution.
Figure 3shows asimplified schematic of alight-scattering photometer. In a
typical instrument, alaser light source, vertically polarized, irradiates asample
solution. The intensity of the scattered light is measured at agiven angle with
respect to the forward direction. Instrumentation is available (see appendix) that
© 2004 by Marcel Dekker, Inc.
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