Separating proteins, biopolymers, polymers and nanoparticles
Field flow fractionation (FFF) is a family of separation techniques which apply hydrodynamic forces to separate a huge diversity of macromolecules. In asymmetrical-flow field flow fractionation (AF4), the solvent and the sample are pumped through a flat channel with a permeable bottom plate that is covered with a semipermeable membrane, the so-called “accumulation wall”. Thus two flow streams are created: the parabolic channel flow and the perpendicularly directed cross-flow through the bottom membrane which drives the molecules towards the accumulation wall. The molecular diffusion based on Brownian motion counteracts this movement. As a result all components reach a distinct equilibrium position which is directly related to their size (exactly: their specific diffusion coefficient). Consequently, bigger particles remain near the membrane, whereas small molecules move higher up into the channel area. In the final elution step - due to the parabolic nature of the channel flow - the small components ride with the faster stream and leave the channel earlier than the larger ones. Following separation the molecules can be comprehensively characterized in terms of concentration, molar mass, size and shape by multi-angle light scattering and related techniques.
Wyatt Technology Corporation, world leader in absolute macromolecular characterization instrumentation and software, integrated Bronkhorst's mini CORI-FLOW instruments in their Flow-FFF system for fast, accurate and flexible measurement and control of the fluid samples. The system offers a routine method to complement size exclusion chromatography (SEC).