Performance of a quadrupole ion trap mass spectrometer adapted for ion/ion reaction studies

The performance characteristics of a new ion trap system adapted for ion/ion reaction experiments are described. Significantly improved mass analysis figures of merit over previously used ion/ion reaction instrumentation have been realized. For example, the present system has a demonstrated upper mass-to-charge ratio limit of at least 150,000, mass measurement accuracy of better than 200 ppm at m/z < 20,000, and mass resolving power of better than 1500 at m/z 20,000. The system also has high flexibility with respect to defining MS' experiments involving both ion/ion reactions and collision-induced dissociation. An experiment is demonstrated involving three distinct ion/ion reaction periods, one collision-induced dissociation step and two ion isolation steps. This experiment has been used to effect the gas-phase concentration, charge state purification, and dissociation of a multiply charged protein ion. Two of the ion/ion reaction periods involved inhibition of the reaction rates of selected ions, referred to as ion parking, whereby resonance excitation is effected during the reaction period. The combination of this high degree of experimental flexibility and improved mass analysis figures of merit over previously used instruments leads to a significantly improved system for the study and application of ion/ion reactions involving multiply-charged ions.