Sheathless capillary electrophoresis electrospray ionization-mass spectrometry interface based on poly(dimethylsiloxane) membrane emitter and thin conducting liquid film

This study develops a sheathless CE-MS interface using a robust PDMS membrane emitter and liquid-film electric conduction. A 3D mold was constructed for casting the device by using a one-step casting procedure. The interface consisted of a 125 m-thick triangular emitter with a 50 m-diameter microchannel, a conducting reservoir, and a 375 m-diameter channel for assembling the separation capillary. The separation capillary was inserted into the 375 m channel and connected to the emitter through the conducting reservoir. The electric contact for the CE outlet was established through a conductive liquid film in the space between the capillary terminus and the 375 m channel. The one-step casting procedure and using a membrane emitter instead of a tapered emitter produced an easily fabricated and robust interface. A stable electrospray was obtained from 30 to 350 nL/min. Analyzing a five-peptide mixture in low-EOF (60 nL/min) and high-EOF (210 nL/min) conditions demonstrated the utility of the interface.