Because of the universal applicability of crossflow as a driving force in field-flow fractionation, flow FFF can be utilized for the separation of most classes of macromoleculcs and particles ranging from less than 1000 molecular weight up to 50 #x3BC;.m particle diameter. This paper focuses on water soluble macromoleculcs. Among the various types of macromolecular materials recently separated by flow FFF at the Field-Flow Fractionation Research Center and reported here are synthetic water soluble polymers or WSPs (including both anionic and cationic polyelectrolylcs) and a variety of biological macromoleculcs, including low and high molecular weight proteins, protein monomers and dimers, WSP-protcin conjugates, lipoproteins, and DNA. These diverse applications can be realized in similar (often identical) channel systems, with only the flowratcs needing adjustments to suit the different samples. Since most of these separations take place based on differences in diffusion coefficient or, equivalently, in Stokes diameter, it is a simple matter to correlate experimental retention with the Stokes diameter and measure the Stokes diameter or diameter distribution of the sample. In this paper we will discuss both the specific applications of flow FFF in this area and the general principles and theory that underlie them.
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