Chromatography Forum

HI,

I'd like to know your opinion and experience on the performance of ion traps and triple quads in LC/MS/MS. I believe ion trap is a better full scan system for unknowns and triple quad for quantitation in matrix. Is it really true now with new ion traps (Thermo Deca XP ou Bruker XCT/HCT).

Pls comment I have to prepare a report for my professor and I'm learning mass spec this year.

I understood that it depends on applications, which ones ?
and Why choose a triple quad or an ion trap ?

any other differenciation factors would help me (MS/MS, mass range, resolution, etc...)

I would use a triple quadrupole if you really do hard core quantitation, as it is more aqurate and assuming that you have molecules that fragment well, you can achieve better detection limits in SRM mode with the triple quadrupole. In terms of resolution a lot have changed in the MS technology as you can find higher resolution triple quadrupoles and ion traps (both from thermo). The highest resolution you can achieve with the triple quadropole from Thermo is 5000 (in general triple quadropoles can achieve much less than that). Now with the introduction of the orbi-trap (again from Thermo) you can normally achieve really high resolutions (theoretically hundrend of thousands, although I think they have spec it for lower). Other differenciations:
Ion trap: Mass range up to early 2000, MSn capability etc.
Triple quadropole: Mass range up to 4000 (depending on the brand etc...), MS2 capability although you can achieve MS3 if you fragment in the source (not very easy to control).

Note that Thermo Deca XP is not a new ion trap any more. Thermo have introduced the LTQ (linear ion trap), which later coupled with an FT and this year they introduced the orbi-trap...

Finally, ion trap mostly used for structural elucidation, triple quadrupole mostly for quantitation. There are also hybrids such as the Q-trap from Applied Biosystems.

Hope the above helps...