**Appendix A**

Re-arranged form of the standard equation for energy transfer in Collision Induced Dissociation. In Collision Induced Dissociation of ions, the relation of centre-of-mass, or "e ffective" (E CM) to laboratory-frame or "nominal" (E lab) collision energy depends:


according to the standard Equation (1).

$$\mathbf{E\_{CM}} = \mathbf{E\_{lab}} \times \mathbf{m\_{TAR}/(m\_{TAR} + m\_{PAR})}$$

For a fixed collision gas employed (e.g., m TAR, nitrogen, MW 28, or argon, MW 40), and for each specific value of "laboratory frame" collision energy, the "centre-of-mass" collision energy decreases as the *m*/*z* value of the precursor ions increase. The variation is not linear, either with the *m*/*z* of the precursor ion, or with the value of the "laboratory frame" collision energy.

Standard algebraic passages allow re-formulating Equation (1) to the linear working Equation (2):

$$\mathbf{E\_{lab}} = \mathbf{E\_{CM}} + \mathbf{E\_{CM}} \times \mathbf{m\_{PAR}/m\_{TAR}}$$

This linear equation allows to "back"-calculate the necessary laboratory frame collision voltage at each value of *m*/*z* of the precursor ion corresponding to a specific constant value of centre-of-mass collision energy.
