Capillary isoelectric focusing – The role of markers of isoelectric point and recent applications in the field

Capillary isoelectric focusing (cIEF) is a very powerful separation technique. However, successful implementation of this technique in various fields of science requires a few prerequisites including a repeatable formation of pH gradient and a set of internal standards (i.e., markers of isoelectric point) to track the actual profile of the pH gradient. Overview of the available isoelectric point markers and their syntheses is presented in this review. Moreover, recent applications of cIEF for analysis of complex larger structures such as viruses, vesicles, and bacterial cells are also reviewed. •Capillary isoelectric focusing principle and history overview.•Importance of tracing of pH gradient profile for determination of isoelectric point.•Discussion of critical parameters for internal standards of pI.•Regular issues occurring during capillary isoelectric focusing analysis.•Review of recent cIEF applications for vesicle, virus, bacteria, and yeast analysis.