The development of a sheathless capillary electrophoresis electrospray ionization–mass spectrometry interface based on thin conducting liquid film

A simple two column sheathless CE/MS interface was constructed using polydimethylsiloxane to fabricate a microdevice allowing facile column alignment and electrical connection. One conducting reservoir, two holes and one 1 mm length microchannel between the holes were fabricated on the microdevice. The two holes were used for connecting separation capillary and ESI sprayer. The hole for ESI sprayer was fabricated at the edge of the conducting reservoir. The ESI sprayer was inserted through the reservoir to the hole so allowing it to be aligned with the separation column. Because the size of the hole was fabricated slightly larger than the outer diameter of the ESI sprayer, the electrical conduction was established through the thin conductive liquid film formed in the space between the ESI sprayer and the hole. The interface design presented was both easy to fabricate and operate and demonstrated good performance. The dead volume did not significantly affect operation as indicated by a demonstrated preservation of separation resolution. The intra-day precision and inter-day precision for peak areas and migration times observed using this interface were found to be less than 12% and 5%, respectively.