Hi,
I'd like to profile and compare a number of metabolities between cell types.
As I am new to LC-MS/MS, please kindly advice which below instrument would be more useful:
- LTQ Orbitrap Velos
- LCMSMS-3200 Qtrap
Is it that a LC-MS/MS firstly performs untargeted profiling of all metabolites, then a 2nd round of MRM for selected metabolites? Could this be performed in a single instrument (e.g. the ones above)?
In that regard,
- Would a lot of starting materials needed?
- Why would a 2nd round of MRM needed, if the metabolities of interest could be profiled in the 1st untargeted run?
Thank you very much
Dear Kay,
If you have a target list of metabolites and you do not care about all the other information of the sample, then a MRM LC-MS/MS determination is sufficient. However, if you are looking for potential biomarkers, unidentified metabolites or you have a suspect list (i.e. a prior knowledge of what may be in your samples, but you do not have the standards), then you should any LC-HRMS(/MS) instrument with a resolving power higher than 20000 (LC-QTOFMS OR Orbitrap). Then you have all the information available: with you target list and your standards, you have the targeted analysis of known metabolites, with your suspect list you can search for potential metabolites and the rest of the peaks can be evaluated by non-targeted approaches.
Dear Kay
The two instruments are very different in what they can do and what information you are going to get from the instruments. The price difference will also give you an idea of how different the technologies for these instruments are.
In general triple quad instruments are good for targeted quantitative analysis but not for identification while a Orbitrap system is a high resolution mass spectrometer with good identifying capability but has some limitations for quantitative work.
As mentioned by Nicolaos it would depend on whether you are quantitating known metabolites or looking for new metabolites or changes in a selected metabolite profile.
Metabolomics is a whole research field on its own and has more requirements than merely looking for a handful of metabolites or biochemical intermediates or quantitating a few selected compounds that may play a role in the pathways affected by some kind of intervention. Very often critical metabolites appear not to change in concentration yet the pathway to, or down line from, this compound could be very different. The sample handling and technical variance of the whole method needs to be considered before making simple decisions that one instrument for making the measurements of potential compounds would be better than another. The whole outcome of the study should be considered and where the study will progress to later should be a major motivation for what type of instrument you should be thinking about acquiring.
The amount of material required depends on how many compounds will be in the sample and how many are required to be quantitated. If the compounds are being separated by LC prior to analysis or whether a straight infusion is to be performed on less complex samples will also affect the sample requirement. Generally a few micrograms of compounds that ionise fairly well would be enough for either instrument, but there are really a lot of factors that need to be considered.
Both systems would allow you to perform on the fly data dependant data collection where, if a compound exceeds a threshold signal limit while interrogating the system on the first quadrupole can trigger a MSMS protocol to assess what product ions are formed from the compound causing the threshold breakthrough.
These two instruments you are interested in are very different and in completely different classes of instrumentation with the capability of the Orbitrap being far greater than the entry level triple quad 3200 system. The answer to your question is what do you want to get out of your research study!
Dear Nikolaos and Duncan,
Thank you so very much for your detailed insights!
From them, I learned a lot about the differences between the two types of mass spectrometers as well as the untargeted / targeted approaches in metabolites analysis.
Definitely, I would need to read much more on this is an exciting and new research avenue.
Good luck to your researches!
Have a nice day :)
Dear Kay Wong,
Orbitrap Velos has an ion trap in the front and an orbitrap analyzer at the rear end of the instrument. So, you actually have ability of what you can do with a Qtrap and additionally have an orbitrap analyzer.
I have used orbitrap instruments orbitrap velos and Qexactive. I believe you can do lot more than what you can do with Qtrap instruments.
Only problem is that you produce lots of data for single injection, so data analsyis is very time consuming.
Dear Kay,
It is not an easy question to answer. I would use an Orbitrap instrument!
Best regards
István
in equal conditions, I mean the use of the state of the art systems for a triple quad and for orbital trap (e. g. 5500 Qtrap and Q exactive), maybe the use of SRM could be an advantage. But for your specific case, the orbi velos should be much better.
I would go with a Orbi for sure as far as untargetted is concerned, as Qtrap will limit in resolution, sensitivity and will be of little use for Untargetted analyses.Using Qtrap if one performs MRM, then one can monitor upto 3-5 transitions to be able to ensure the identification of the correct isomer or remove noise/ background issues.
targeted Quantification, then go to Qtrap.
untargeted identification, then go to LTQ.
Dear All
Please suggest for untargetted metabolomics, Orbitrap or Q-TOF? Which one is better.
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