Concept of a DESI ion source. The DESI ion source is a pneumatically assisted microelectrospray ion source capable of delivering a coaxial sheath gas at up to 350 m/sec. High-voltage contact is applied at the liquid junction between solvent delivery lines or at the spray nozzle. The sample is in the ordinary ambient environment. (Reprinted with permission, © 2007 Scion Publishing Ltd.)