Field-Flow Fractionation Techniques for Polymer and Colloid Analysis Helmut Cölfen, Markus Antonietti Max Planck Institute of Colloids and Interfaces, Colloid Chemistry Department, Am Mühlenberg 2, D-14476 Golm, Germany E-mail:
[email protected] Field-flow fractionation (FFF) is a family of flexible analytical fractionating techniques which have the great advantage that separation is achieved solely through the interaction of the sample with an external physical field and without a stationary phase. This has the ad- vantage of avoiding the large variety of problems due to non-specific sample interactions with column materials associated with other chromatographic techniques. Furthermore, the range of information accessible is very broad and often complimentary when various FFF techniques are applied, so that even very complex systems with broad size distribution, heterogeneous mixtures or strongly interacting systems can be characterized. The range of particle sizes or hydrodynamic radii which can be separated is very broad ranging from 1 nm to 100 µm, covering the entire colloidal, polymeric and even most of the microparticle domain. No other fractionating technique can cover about 5 orders of magnitude of the par- ticle size, even with complex distributions. This review will introduce the basic principles, theory, and experimental arrangements of the various FFF techniques focusing on the most relevant for praxis: Sedimentation-FFF (S- FFF), Thermal-FFF (Th-FFF) and Flow-FFF (Fl-FFF). In a second part, selected applications of these techniques both to synthetic and biological samples will illustrate applications un- der a variety of conditions, where problems and potential pitfalls as well as recent develop- ments are also considered.