Instrument‐independent database for collisionally activated dissociation in RF‐only quadrupoles. The case of C 2 H 3 O + and C 3 H 7 +

Dynamically correct (i.e., instrument‐independent) branching ratios can be measured under single‐collision conditions in tandem mass spectrometers incorporating RF‐only quadrupole collision cells. The absolute branching ratios were measured as a function of the center‐of‐mass interaction energy E CM for the collisionally activated dissociation (CAD) of CH 3 CO + (m/z43) from several source compounds (ethanol, oxirane), and CH 3 CO‐X (where X = H, CH 3 , CH 3 CH 2 , CH 3 CO, CH 3 COCH 2 , and C 6 H 5 )). The energy dependences of the branching ratios for C 2 H 3 O + from CH 3 CO‐X source compounds are quite distinct from those observed for C 2 H 3 O + from ethanol or ethylene oxide, or for the C 3 H + 7 ions (also m / z 43) from n ‐pentane. Hence, one can use the CAD of m / z 43 to distinguish CH 3 CO‐X compounds from other source compounds, including sources of C 3 H 7 + ions. Therefore, the characteristic branching ratios of ionic substructures may provide for tandem mass spectrometry a „fingerprinting” capability analogous to the use of group frequencies in infrared spectroscopy.