When (laser) light interacts with a macromolecule, the oscillating electric field of the light induces an oscillating dipole. This oscillating dipole will re-radiate light. The intensity of the scattered light depends on the polarizability, and the polarizability depends on the molecular weight. This property makes light scattering a valuable tool in for the characterization of macromolecules and one of the few absolute techniques to measure molecular weights.
For scientists working with macromolecules two light scattering techniques are of major importance:
measures the time averaged scattering intensities at one or more specific scattering angles as a function of angle, concentration, or both to determine the weight average molar mass, the 2nd virial coefficient and the z-average of the radius of gyration
measures the time dependence of the intensity of the scattered light to determine the translational diffusion coefficient and hence the hydrodynamic radius
SLS and DLS instruments are either available as detectors to be attached to a chromatographic system or as batch/stand-alone instruments. Batch/stand-alone instruments measure batch properties (average values only) while the advantage of hyphenation with a chromatographic systems is that this allows to measure distributions.