Field Flow Fractionation

Field-Flow-Fractionation (FFF) is a chromatography-like analytical technology to separate molecules and particles ranging from a few nanometers to a few micrometers (respectively M_w = 1·10³ – 1·10⁸ g/mol) without the presence of a stationary phase and therefore without the application of shear force.

Asymmetric Flow Field-Flow Fractionation (AF-FFF or AF4) belongs to the group of Field-Flow Fractionation methods. AF4 is a relatively new and efficient method for rapid fractionation and high resolution characterization of various polymers as well as nanoparticles and –capsules as investigated in our department.

Separation in AF4 occurs in a thin flow channel. The laminar channel flow carries the sample through the channel. Due to this channel flow a parabolic flow profile is generated. Perpendicular to this channel flow a second flow, the cross-flow, generates a force field, which drives the molecules or particles in the direction of the channel bottom. Smaller particles will diffuse back into the channel faster than larger particles because of their larger diffusion coefficients. As a result various components are arranged into regions of different flow velocities and therefore smaller molecules or particles are eluted faster than larger components.

Determination of:

- the presence of species with different size without the application of shear force
- fractionation for further analysis of the different size populations

Equipment / sample requirements:

Postnova AF-FFF system coupled with UV and RI-detector
- only aqueous systems
- no interaction with the channel membrane

Literature: