Design and performance of an electrospray ion source for magnetic-sector mass spectrometers

An electrospray ion (ESI) source capable of operating at accelerating potentials of up to 11 kV has been designed and fabricated. The ESI source has been shown to deliver ion beams with a total current up to 20 pA and an emittance of 2–3 mm mrad in analysis of the peptide gramicidin S (molecular mass 1140.7 Da) and the protein bovine insulin B chain (molecular mass 3495.9 Da). Coupled to a two-sector tandem mass spectrometer, the ESI source produced efficiently the multiply charged ions of proteins, such as bovine ubiquitin (molecular mass 8564.8 Da) and cytochrome c (molecular mass 12327 Da). The high ion currents and high kinetic energies of the electrospray ions (up to 200 keV) characterize this ESI source as a powerful tool to be used in structural analysis of macromolecules by collision-induced dissociation.