Mass resolution of 11,000 to 22,000 with a multiple pass quadrupole mass analyzer

CO+ and N-2(+) are separated with resolution of 11,000 [full width half max imum (FWHM)] using a conventional quadrupole mass spectrometer by applying square wave voltages to the entrance and exit lenses to trap or reflect the ions for multiple passes. A resolution of 22,000 (FWHM) with 63% of the to tal signal remaining is attained using multiple passes when ions are stored between injection pulses. Gated ion extraction also reduces the mass shift and number and intensity of artifact peaks and permits better resolution c ompared to the performance obtained when the ions are injected continuously . (C) 2000 American Society for Mass Spectrometry.