Electrostatic ion guide using double cylindrical electrode for atmospheric pressure ionization mass spectrometry

A novel electrostatic ion focusing lens that consists of two cylindrical electrodes positioned coaxially with each other is described. Square openings are formed in the inner electrode and their angular positions alternate by 90 degrees with respect to the neighboring openings in the axial direction. When a potential difference is applied between the inner and outer electrodes, an electric field penetrates into the interior of the inner electrode through the openings. In the capillary electrophoresis/mass spectrometry analysis of peptides, use of the lens makes it possible to apply a higher voltage to the postacceleration dynode and the signal to background ratio is improved by a factor of 7. (C) 1996 American Institute of Physics.