Dear colleagues,
Lately I've encountered some confusion regarding the "hybrid-type" Orbitrap mass spectrometer. May you please advice regarding whether the below terminologies are referring to the same configuration (or can be used interchangeably)?
(1) For LTQ-Orbitrap, "LTQ" stands for the "Linear trap quadrupole". Nevertheless, some other papers I read also called "LTQ" as "Linear Ion trap". To my knowledge, the LTQ essentially is serving the role for ion trapping, ion selection, ion fragmentation and low resolution detection. In this regard, so what’s the suffix “Q” in LTQ stands for (if there’s no quadrupole functioning)?
(2) From earlier literatures, I encountered the term “Quadrupole Ion trap”. Is it the same / different?
(3) As I am new, I am currently reading some references from 2005 for the basic knowledge on “Ion-trap CID fragmentation”. Inevitably, such books only describe the principle for “Quadrupole Ion trap CID”. Is the same CID principle holds true for Linear Ion traps? (as they are both based on resonant excitation, using low collision energy)?
Thank you very much.
Although Rachel is essentially correct, I'd like to add some information:
- Hybrid instruments are such that they combine two types of mass spectrometer (quadrupole and orbitrap here, or QTOF = Q-time-of-flight, etc.)
- In the older literature, before the “linear” ion traps, all ITs were of the hyperbolic type (of "circular" symmetry), also called "3-D ion traps" now. The linear ITs are sometimes called 2-D referring to their elongated geometry. The 2-D traps can trap more ions before the space charge limit, so they have a better response and a wider dynamic range. In principle, the two types of traps work quite similarly (He buffer gas, ion selection, CID with MSn possibilities, depending on the software…).
- You probably refer to the “quadrupole mass filter” (basis of the quadrupole mass spectrometer QMS) when you cite the quadrupole: this is another use of the quadrupolar fields, which give rise to “stability diagrams” = plots of zone of stable trajectories as a function of applied potentials. This means either transmission (or non transmission) of a given m/z (use as mass filter) or trapping (or non trapping = ejection) of given ion(s).
Hi Kay,
As mentioned above the linear 2D is the evolutionary successor of the 3D ion trap.
To the excellent answers above I would like to add this study which actually compares the performance between the two.
http://pubs.acs.org/doi/pdf/10.1021/ac051486a
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