Analysis of Peptides and Proteins by Native and SDS Capillary Gel Electrophoresis Coupled to Electrospray Ionization Mass Spectrometry via a Closed-Circuit Coaxial Sheath Flow Reactor Interface

A simple and widely applicable coaxial sheath flow reactor interface (CSFRI) is introduced for easy and robust connection of liquid-phase microseparation methods to mass spectrometric detection, especially for capillary gel electrophoresis analysis of proteins and peptides including SDS-protein complexes. The interface readily accommodated post-column reactions prior to MS detection. It was demonstrated that this novel closed-circuit connection allowed the utilization of non-MS friendly buffer components without significant ion suppression and supported stable electrospray. In SDS capillary agarose gel electrophoresis mode, addition of γ-cyclodextrin to the sheath liquid efficiently removed the SDS content of the sample and the background electrolyte in the flow reactor section by inclusion complexation, while maintaining good separation efficiency and decreasing ion suppression.