As size exclusion chromatography (SEC), Flow Field Flow Fractionation is a separation technique that assesses the size distribution of the molecules via theoretical equations or representative standards. In FFF technique, high-resolution separation is achieved within a very thin flow against which a perpendicular force field is applied. It takes place in an asymmetrical flat channel (A4F) or in a hollow fiber (HF5). Separation depends on the Brownian diffusion coefficient of the molecule / particle, and thus on its size. Multi Angle Light Scattering detector (MALS) is used for the determination of the absolute molar mass and size determination of macromolecules / nanoparticles. In FFF separation, no stationary phase is required that avoids interferences with the samples. Consequently, for very high molar weight polymers, shearing forces do not apply. The entire separation is smooth, fast, and non-destructive without a stationary phase that may interact, degrade, or alter the sample.

Field-Flow Fractionation-based techniques are powerful tools for characterizing polysaccharides and for monitoring the potential polydispersity and/or polymodality. They are powerful tools especially in the case of drug delivery. In a Pharmacopeia approach, these techniques must be coupled to complementary techniques for a full characterization of products. Viscosity measurements have been conducted together with A4F-UV-MALS and to study the size and size distribution of exopolysaccharides.