Light Scattering is an absolute technique for the determination of molecular weight of macromolecules. This technique is independent of the column calibration procedure and determines the ABSOLUTE or the TRUE molecular mass DIRECTLY. Light scattering is used when the true value of molecular weight is of great importance. The weight-average molecular weight value obtained by light scattering can be matched with the values obtained by spectroscopy techniques. Light scattering detector theory is based on Raleigh’s equation relating the intensity of scattered light, R(θ), to the molecular mass of macromolecules, Mw, and the concentration of sample solution, c:
This technique can be employed in batch mode or in-line with size exclusion. In GPC/SEC, light scattering is employed to determine the absolute molecular weight for each fraction of distribution.
Light scattering also provides Radius of Gyration, Rg, by measuring the angular dependency of the scattered light. PolyAnalytik is equipped with both Low Angle Light Scattering (LALS) and Multi Angle Light Scattering (MALS) for the most accurate absolute molecular weight and radius of gyration measurements.