Asymmetric flow field flow fractionation

[1] AF4 is distinct from symmetrical Flow FFF because it contains only one permeable wall so the cross-flow is caused only by the carrier liquid.

The cross-flow is induced by the carrier liquid constantly exiting by way of the semi-permeable wall on the bottom of the channel.

AF4's applications are flexible for many analytical conditions where a column-based method would be unable to properly separate the desired particles.

AF4 and other FFF methods have been extensively used in environmental research on the impact of nano materials[2] and to characterize condensed tannins oxidation.

[3] For high molar mass and branched polymers, AF4 has been shown to achieve good separation, whereas SEC fails,[4] and AF4 has been applied to polyolefines at temperatures above 150 C.[5] Detection methods are the same as for FFF in general, UV is most popular as a concentration detector, but most AF4 systems include a multi-angle light scattering detector for direct measurement or size and molar mass.