Capillary electrochromatography of biomolecules with on-line electrospray ionization and time-of-flight mass spectrometry

Capillary electrochromatography (CEC) is considered a hybrid of liquid chromatography and capillary electrophoresis. It is expected to combine the high peak efficiency of capillary zone electrophoresis with the versatility and loading capacity of HPLC to bring about another high-performance MS-compatible chromatographic system. This paper explores the potential of CEC coupled with the electrospray ionization and time-of-flight mass spectrometry in biochemical analysis. The packed columns used in this study were tapered at the outlet to retain the packing material, thereby obviating the need for an outlet frit. Electrosmotically driven solvent gradients were employed for the separation of phenylthiohydantoin (PTH)-amino acids by reversed-phase chromatography, and a time-of-flight (TOF) mass spectrometer was employed as the detector for the CEC column effluent. The effect of CEC operating parameters, such as gradient shape, column length, and electric field, on the analytical results from the separation and MS detection of a standard mixture of PTH-amino acids was investigated. Particular attention was paid to the effect of sheath flow-rate, sheath composition and mass spectra acquisition rate on the performance of the electrospray TOF-MS.