Tuesday, May 5, 2020

Mixed Data Acquisition -- DIA + DDA in the same run!

Which is better?

Data Dependent Acquisition (DDA)
Data INdependent Acquisition (DIA)

Presenting -- MIXED Data Acquisition!

To help clarify this idea, I outsourced the design of a schematic of a "tribrid" orbital mass spectrometer device to some professional illustrators.

Tricked you! I did...part of this...myself! 

When you're doing DIA in your fancy instrument, the ion trap is doing a lot of nothing. Why not acquire DDA MS/MS spectra there while your Orbitrap is busy getting MS1 and DIA data? It's like spectra for free! 

Obviously, you'll need to worry about cycle time -- which is tough to calculate on your own on the Tribrids -- and consider the matrix and chromatography time, etc., etc., but there are key advantages. 

You know those coeluting peaks that kind of smear together in the XIC, particularly in the high mass range where your resolution is lower? These authors demonstrate that they can use the DIA windows to separate those out and improve their quan. The paper is pretty short -- proof of concept, but it doesn't take much imagination to see the potential advantages. Use your MS/MS to generate your libraries that you use for DIA quan? 

If there is a downside, I sure don't see it. You paid extra to get that ion trap back there. You might as well make it do stuff!  

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