In theory, a complex sample could be separated to its constituents via elution from the Ion-Trap to a triple-quad, using the elution mass to set confinement ranges of the first quadrupole to increase resolutions prior to CID and measurement in the final 2 quadrupoles. Would such a device be practical? Or does it already exist?
This combination is technically realized in LIQ-Orbitroap system, combination with QqQ will nto help.
In general, I think a quadrupole prior to the ion-trap makes more sense to select ions stored in the trap. This is for example the case in the Q-Trap instruments from ABSciex or QExactive from Thermo. However, it is true, the rather bad resolution of the precursor mass selection is a instrumental weakness of the Orbitrap instruments. It is at best 0.5 m/z and in extreme cases, i.e. precursor selection for HCD on an Orbitrap LTQ, good values can be 4 m/z for the mass window.
This is possible if you use stored waveform inverse fourier tranfrom (SWIFT) technique to separate the desired ions inside the ion trap and after the selection the mass selected ions can be injected into the first quad of the triple quad instrument, In the second and third quadrupole stage you can perform cid experiments.
Your question doesn't make sense because top–down and bottom–up refer to sample preparation steps before mass spectrometry analysis.
i apologize, the use of term bottom up approach would suggest enzymatic digestion prior to sample analysis, may i correct it to "shotgun and top-down". Although the question was directed at the coupling of devices in said manner. To expand the question i was more interested in the idea of using the IT as sample separation instead of traditional separation techniques. Thank you all for the enlightening technical insights.
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