A NEW LINEAR ION-TRAP TIME-OF-FLIGHT SYSTEM WITH TANDEM MASS-SPECTROMETRY CAPABILITIES

A new hybrid linear ion trap time-of-flight mass spectrometer has been constructed and the first results for tandem-in-time MS/MS in a 2-dim ensional Paul trap are presented. The instrument consists of an electr ospray ionization source and two radio frequency (RF) only quadrupoles operating at a pressure of 7 mTorr N-2 which are coupled orthogonally to a linear TOFMS. Ions are trapped in an RF-only quadrupole through the application of timed stopping potentials on the entrance and exit apertures. Through the coupling of an auxiliary waveform generator on one pair of the ion trap rods a small dipolar excitation voltage is su perimposed on the quadrupolar electric field. This voltage is used for precursor isolation via broadband excitation and collision induced di ssociation through mass selective resonant excitation. Instrumental pe rformance and choice of operating parameters are demonstrated by recor ding fragment spectra for +3 ions of renin substrate and fl ions of re serpine. TOFMS mass resolution (m/Delta m)(FWHM) is as high as 740 at m/z = 609. Fragmentation efficiency is greater than 50% and excitation mass resolution is 60-75. (C) 1998 John Wiley & Sons, Ltd.