SEPARATION AND DETECTION OF CLOSELY-RELATED PEPTIDES BY MICELLAR ELECTROKINETIC CHROMATOGRAPHY COUPLED WITH ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY USING THE PARTIAL FILLING TECHNIQUE

Closely related peptides such as neurotensin and angiotensin analogues were separated by capillary zone electrophoresis using a nonionic sur factant, sucrose monododecanoate, as a micelle forming reagent. These peptides were detected by an on-line coupled mass spectrometer using a n electrospray ionization interface. However, the presence of the mice lles in the separation solution drastically reduced the sensitivity of the mass spectrometer. Therefore, a partial filling technique was emp loyed to prevent the micelles from entering the mass spectrometric int erface. A part of the capillary from the injection end was filled with the micellar solution in this technique. Analytes passed through the micellar zone during the electrophoresis and when the separated analyt es reached the detection end of the capillary, the micellar zone was s till behind the analyte zones, because the nonionic surfactant moved v ery slowly in acidic conditions. Thus the technique was very useful fo r mass spectrometric detection for CE when the micellar solution was e mployed for separation. The optimization of separation and detection c onditions was investigated.