Field-flow fractionation: Questions, Observations, and Understanding

Field-flow fractionation (FFF) is a wonderful set of techniques for the separation of macromolecules and particles. The subtechniques of sedimentation, flow, thermal and electrical FFF all offer unique features for separating samples of biological, environmental, and industrial origin.

Although the development of killer applications like vaccine characterization have made asymmetrical flow FFF an indispensable technique for quality assessment, the continued innovation and modification of these subtechniques has not been widely pursued.

In this talk, I will focus on a number of insights that surround the basics of FFF. These include:

1) FFF has a large dilution factor which results from using a small fraction of the channel volume for separation. Is this holding up the use of FFF as a component of a multidimensional separation?

2) The compressing of the zone against or into the accumulation wall can lose sample due to adsorption and distort the sample when delicate particles like exosomes, squishy hydrogels, etc. form dimers and trimers at the wall surface. How can this be minimized?

3) Is the detector used in FFF, for example the multi-angle light scattering (MALS) detector, only as accurate as the separation quality of the FFF fractionator in front of it?

4) The FFF process requires a velocity gradient in the fluid or it can’t develop a separation. Is this unavoidable or are there other ways to develop separation?

5) Particle simulation methods were developed back in the early 1980’s to calculate FFF retention with both low and high retention. The computer demands were excessive. Is that still true?