Micellar electrokinetic chromatography of enkephalin-related peptides with laser-induced fluorescence detection

Eight enkephalin-related peptides were derivatized using fluorescein isothiocyanate (FITC), and the derivatization products were separated and detected by capillary electrophoresis with laser-induced fluorescence detection. The optimum molar ratio of FITC and peptide for derivatization was found to be 40:1, and 5 mmol/L sodium borate buffer (pH 9.2) was selected as derivatization media in order to get the high efficiency. Enkephalin-related peptides were completely separated in the pH range of 10.51-10.60 in a running buffer consisting of 100 mmol/L sodium borate and 60 mmol/L sodium dodecyl sulfate (SDS). The detection limit for these eight enkephalins ranged from 0.18 to 2.25 nmol/L, and the linear response range was 1.0 x 10(-6) to 1.0 x 10(-9) mol/L with correlation coefficients between 0.9947-0.9988. A separation efficiency as high as 380000 theoretical plates could be obtained for these analytes.