Magnum Ion Trap Detector (ITD) is a benchtop GC/MS product of Finnigan MAT.
It operates in the GC/MS mode only, whith an upper mass limit of 650
daltons. The system is routinely operated in electron impact and chemical
ionization positive ion mode. This mass spectrometer is quit different from
others in a sense that ionization, mass analysis, and detection, occur in
the same chamber. This feature contributes to the high sensitivity often
observed with respect to quadrupole benchtop type instruments.
The ion trap assembly contains three stainless steel hyperbolic
These electrodes form a cavity in which
ionization, fragmentation, storage, and mass analysis occur.
At the GC column exit, sample molecules are introduced to the ion trap cavity, where they interact with energetic electrons (EI mode) or with preformed reagent positive ions (CI mode). Electrons are emmitted into the cavity only during a fraction of time of the scan. This fraction of time is refered to as ionization time and it's automatically controlled by the automatic scan function. This function coordinate ionization, storage, and ion ejection time for optimum sensitivities and peak shapes. After the ionization time is expired, the RF voltage applied to the central ring ramps. Ions with different masses become successively instable and are ejected to the detector. Finaly ions are collected and the signal is multiplied. The amplified ion current enter the electrometer circuit for further signal processing.