LC-MS Vs LC/MS TOF Vs QTOF

[Karen01]

UI know this is a very general question but I would really appreciate it if someone could give me a quick high level overview.

I don't have much of an MS background and What I have is ancient GC-MS experience. I know Tof is used for larger molecules, often proteins but maybe others. Most of my work for the last 15 years has been small molecule LC and GC with non MS detectors and now I need to get a basic handle on this methodology. I under stand the BASIC theory of TOF from an MS course I took in the 80's but that's about it.

I'm trying to get an understanding what are the overlapping and different types of applications one would use LC-TOF and LC-QTOF for.

I realize a QTof can be used in essentially just as a TOF so a QTOF can do anythings TOF. So type of things would Tof alone be good for and what does QTOf add? What are the type of things that can ONLY be done by QTof?

Thanks,
- Karen

[Gaetan Glauser]

Using an QTOF you can perform selected MS/MS experiments, neutral loss etc. all kinds of things only a tandem mass spec can do.

With a single TOF you will essentially get accurate mass pseudo-molecular ions together with adducts and possibly in-source fragments. If two compounds perfectly co-elute, you won't be able to associate fragment ions produced in the source to parent ones. Also fragmentation is in principle more efficient in a collision cell than in the source.

Finally a QTOF is supposed to achieve pseudo-MS3 (fragmentation in the source, selection of a fragment in the quad and fragmentation of the fragment in the collision cell).