Abstract
Analytical ultracentrifugation (AUC) is a classical absolute technique for polymer analysis. However, it is also a very powerful technique for the characterization of nanoparticles as already established almost 80 years ago by the pioneering work of Svedberg and coworkers. AUC allows for sample fractionation either due to size (sedimentation velocity/sedimentation equilibrium) or due to the chemical structure expressed as particle density (density gradient). Thus, the direct measurement of particle size resp. particle density distributions is possible with high statistical accuracy and a very high resolution even in complicated mixtures. Beside an introduction to AUC, this article will outline these possibilities for nanoparticles with sizes ranging over the entire colloidal range and also for organic-inorganic hybrid particles, showing the versatility of AUC. Also, a guide to AUC textbooks, internet discussion platforms, and modern free evaluation software is provided. The combination with other techniques such as light scattering or field-flow-fractionation can gain a deep insight into complex hybrid particle mixtures. This points toward future global analysis possibilities for the simultaneous determination of distributions of several particle characteristics such as size and density.