4 Basic Experiment Types

Although the basic ultracentrifuge theory is well known and documented, some of the basic equations shall be repeated here wherever necessary to understand special evaluation methods, even though some of them were developed for the analysis of polymer solutions. The basic equation for ultracentrifugation experiments is the Lammequation (1), which describes the local concentration variations of the sample in the ultracentrifugal field with time owing to the sedimentation and diffusion transport processes: ^[31]

Based on this equation, there are four basic types of experiments that can be performed with an analytical ultracentrifuge. Each of them can deliver its own range of physicochemical information on the sample. The different experimental approaches with a focus on colloids will be treated in the following subsections. Table 1 outlines the characteristics of each experiment type and the most important accessible parameters. However, although most experiments for the analysis of colloids are covered by the four basic experiments below, special experiments can also be described by the Lamm equation, together with additional parameters. Examples of this are the swelling pressure equilibrium experiments a special case of sedimentation equilibrium experiments for gels or synthetic boundary crystallization experiments, which are a special case of synthetic boundary experiments for the in situ formation of crystals.