Liquid Chromatography Detectors - Liquid Light Scattering Detectors > Page 77



where, (a) is the attenuation constant,
 (w) is a function of the refractive index,
and (Rf) is Rayleigh's constant


Now the molecular weight (Mw) of the solute is related to the Rayleigh factor by the following expression,



where (c) is the concentration of the solute,
(A2) is a function of polymer-polymer interactions,
and (K) is the polymer optical constant.




where (h) is the solvent refractive index,
(l) is the wavelength of the light in vacuum,
and (N) is Avogadro's number.

Thus, a basic relationship can be developed between the molecular weight of the scattering material, the intensity of the scattered light and the physical properties of the materials and equipment being involved. However, constants are in used, the magnitude of which are difficult to determine. In practice a simple graphical procedure is used to determine the molecular weight of the solute without the need to determine all the pertinent constants. Rearranging the equation