Fluorescence detection of proteins and amino acids in capillary electrophoresis using a post-column sheath flow reactor

A simple laser-induced fluorescence detection method for proteins and amino acids in capillary electrophoresis is reported. A sheath flow cell is util ized as a post-column reactor for fluorescence derivatization of proteins a nd amino acids by addition of o-phthaldialdehyde-2-mercaptoethanol to the s heath fluid. With the use of a 50 mu m I.D. capillary, the limits of detect ion for carbonic anhydrase are 0.73 nM or 1.8 amol which represents a five- and two-fold improvement, respectively, over the best results previously r eported for post-column detection. In addition, separation efficiencies up to 8.07.10(5) an achieved, and the detector response is Linear over three-o rders of magnitude. These results demonstrate that mixing is adequate and t he reaction kinetics are rapid enough to provide sensitive detection with t his approach. Also, because this post-column derivatization scheme requires no instrumental changes to a typical sheath flow cell detector, the system can be used for detection of pre-column labeled analytes and for native fl uorescence detection. (C) 1998 Elsevier Science B.V. All nights reserved.