Indirect photometric detection in capillary electrophoresis using buffered electrolytes. Part I: principles

Indirect photometric detection in capillary electrophoresis is valuable as a detection method for nonabsorbing low molecular weight ions. The general operating principle rests in the displacement of an absorbing ion - sometimes called the probe ‚ÄövÑvÆ added to the electrolyte by the analyte co-ions, which are ions of the same charge polarity, as they migrate under the influence of the electric field through the capillary. Despite this apparent simplicity, the choice of optimal parameters, and especially of electrolyte composition, can be quite challenging. This first installment of a two-part series outlines the principles and approaches to indirect detection.