4.5.5.1.1.2 Sheathless Flow Interface

Several methods of uniting the CE capillary with the ESI system exist  However, in all of these systems, electrochemical processes such as oxygen and hydrogen formation can occur. The formation of gas bubbles that are not frequently vented can cause increased resistance. In the tri-axial system, evolved gases are frequently flushed due to sheath flow and/or the nebulizer gas, but in sheathless systems increased resistance can form a substantial problem.

In 2007, Moini published a technique that does not require sheath flow and does not create electrochemical processes at the electrodes. A thin, porous segment of glass acts as a liquid and electrical contact outside the capillary. The tube is either grounded or placed at the ESI voltage. This system has recently become available commercially through Beckman-Coulter.