The efficiency of ion transfer between the quadrupole mass analyzers and the Q2 collision cell in a triple quadrupole Mass Spectrometry (MS) is critical for instrument robustness and sensitivity- qualities that make triple quadrupoles the reliable “work-horses” they have become in quantitative MS today.
Q2 is an RF only non-mass filtering quadrupole containing only an inert collision gas such as Ar, He or N2 to provide collision induced dissociation of the precursor ion selected in Q1. One challenging design requirement is that there should be no collisions in Q1 or Q3, which are in close proximity in the same vacuum region to serve as mass filters and scan for parent and dissociated ions respectively. Another challenging design requirement is that the ion beam should be narrow and centered at the entrance of each quadrupole but at the exit of the previous quadrupole the beam is wide and divergent and needs to be collimated in order to achive best sensitivity.
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