Chapter 17 Field-flow fractionation for molar mass characterization of polysaccharides

Abstract

This chapter describes field-flow fractionation (FFF) for the molar mass characterization of polysaccharides. FFF is a separation method performed in an open, unpacked channel and is technically very similar to column liquid chromatography. The difference is that it does not involve any stationary phase but only a mobile phase. The family of FFF techniques is designed to improve the possibilities of characterizing macromolecules, colloids, and particles. The main reason for using the methods in the characterization of the molar mass of polymers and other macromolecules is that the retention time of components separated in an FFF channel depends on their diffusion coefficients and, sometimes, on other component parameters. Depending on the nature of the applied field, the FFF methods are divided in various submethods. In sedimentation FFF (SdFFF), a sedimentation field is applied. It can be created in a centrifuge—for example, an FFF channel is part of the rotor in a centrifuge. In thermal FFF (ThFFF), two-channel walls have different temperatures so that a temperature gradient occurs across the channel. In flow FFF (FlFFF), the field is caused by a secondary flow of the carrier liquid across the channel's accumulation wall.