Capillary electrophoresis Principles

Capillary electrophoresis is a technique for analyzing compounds in the liquid phase, be they small inorganic ions, small molecules such as amino acids, peptides or active pharmaceutical ingredients, or macromolecules such as proteins, polymers and DNA, or even nanoparticles or viruses. It is performed within a capillary of small internal diameter (a few tens of micrometers) filled with a separation electrolyte, and requires the application of an electric field. As with liquid chromatography, there are several separation modes, depending on the composition of the electrolyte and the possible presence of a stationary phase in the capillary, which enable compounds to be separated according to their charge/size ratio, hydrophobicity, chirality, size or isoelectric point, for example. This diversity of separation mechanisms, combined with very high efficiencies, rapid, automated, low-cost and miniaturized analyses, makes this technique indispensable in many applications. This article presents the different parameters influencing compound separation, defines the fundamental quantities and describes the various phenomena that can lead to a reduction in analysis performance. The principle of each separation mode in capillary electrophoresis is presented and illustrated by examples of various applications (inorganic ions, drugs, pollutants, proteins, DNA, etc.).