Instrumentation and methods for ion and reaction monitoring using a non-scanning rectilinear ion trap

A method of single ion or single reaction monitoring which avoids high RF voltage scanning is identified and implemented in an ion trap mass spectrometer. A rectilinear ion trap (RIT) mass spectrometer was constructed and characterized and used to develop a simple method of monitoring targeted compounds without using RF voltage scanning. The ions were first isolated, and then ejected axially from the aperture in one of the z-electrodes for detection. Various ion monitoring modes, including selected ion monitoring (SIM), multiple ion monitoring (MIM), and selected reaction monitoring (SRM), are demonstrated using RF/DC isolation or waveform isolation in combination with the axial DC pulses to eject and detect ions of particular mass/charge ratios.