Interfacing microchip capillary electrophoresis with electrospray ionization mass spectrometry.

Microfluidic devices are a unique enabling technology for chemical separations, modification, and synthesis that are ideally suited for the manipulation of low volume samples on the order of a few nanoliters in volume. Complex patterns of capillary-sized channels with zero dead volume connections are the distinguishing features of many microfluidic devices. Concurrently, mass spectrometry has undergone further development, and is now arguably the method of choice for structural characterization of mass- and volume-limited samples. The production of ions in the gas phase from the solution phase is critical for direct coupling of fluidic devices with the mass spectrometer, and the electrospray ionization (ESI) sources are well suited for this application. Micro- and nanoflow ESI interfaces are ideal for these applications as they cover flow rate ranges from the hundreds to a few nanoliters per minute, which are the same as the flow rates used by most microfluidic devices. Herein, the assembly and operation of a simple ESI interface for coupling a microfluidic device and mass spectrometer is described.