a) Does tandem MS require a collision chamber to be part of the instrumental setup?
Tandem MS does only require that m/z-analyzed ions have a chance to react in some way prior to a next stage of m/z analysis. If the ion remains intact the experiment will tell us. Fragment ions are only observed if the ions do decompose independent of whether there was an additional step of ion activation involved or not.
b) Right or wrong? Decide and give a brief statement.
- Metastable ions desompose on the picosecond time scale:
Wrong. The time-scale for metastable ion decompositions is normally in the range of several microseconds.
- Metastable ions do only occur on magnetic sector instruments:
Wrong. Metabstable ions occurs whenever ions dissociate after having left the ion source.
- Field-free regions are required for metastable ion dissociations:
Wrong. Metabstable ions occurs whenever ions dissociate after having left the ion source – in any type of instrument, inside or between mass-analyzing devices.
- Only metabstable ions dissociation in field-free regions can be analyzed on the subsequent stage.
Right. The others are lost as their trajectories become instable.
- Collision-induced dissociation is frequently employed for fragment ion generation from otherwise stable prescursor ions.
Right. CID is used so frequently that people have started to believe CID would necessarily be part of every tandem MS experiment.