A coaxial extractive electrospray ionization source

An extractive electrospray ionization (EESI) source design is presented to improve the reproducibility of the interactions occurring in EESI. This design uses three concentric capillaries to deliver the solvent, sample and nebulizing gas. Coaxial EESI was found to improve the inter-experiment variation by a factor of four and intra-run relative standard deviation by a factor of 2.4. Unlike most standard EESI designs, the device has the form factor of a standard electrospray emitter and can be used without any further instrument modifications.