Postcolumn reactor in capillary electrophoresis for laser-induced fluorescence detection

The construction and utility of a postcolumn reactor in capillary electrophoresis using o-phthaldialdehyde/2-mercaptoethanol (OPA/2-ME) as the fluorescent labeling reagent and laser-induced fluorescence detection are described. The reactor is based on a coaxial design consisting of two narrow-bore capillaries. The reagent is electroosmotically pumped into the reaction capillary and the flow is controlled independently by a separate high-voltage power supply. The response is linear over at least two orders of magnitude. Mass limits of detection are in the low attomole range for various amines, amino acids and proteins. The suitability of the system for single-cell studies is demonstrated with human erythrocytes.