Thermo LTQ vs. Agilent Q-TOF

[gckiv]

Hi All,

I'm sure this has been discussed before, but we're upgrading our LCQDeca to something with faster scanning, better resolution at the high end, and still allowing for MS/MS and MSn. We've basically narrowed it down to Thermo's LTQ (or the LXQ) or Agilent's Q-TOF. Both sound fantastic for our applications....primarily peptide mapping, intact pure proteins, some smaller molecules, etc. (QC lab). Does anyone have experience with both of these units? I don't want to start a debate between the Thermo and Agilent die-hards, but we want some input from other users. We'll probably add on a new LC also, possibly a new high-pressure unit. Since we're in a regulated environment, a nice audit trail software feature (vs. the cumbersome ChemStore) would be appealing as well. Thoughts and opinions?

[ods-at-pacific]

I am curious as how you come down to these two instruments. To me it is a little like comparing apples and oranges. The LTQ is essentially a unit resolution instrument that is capable of MSn and has a good liner dynamic range for quantitation. The Agilent Q-TOF will allow only for MS/MS, has mass accuracy to the nearest 1/10 millimass unit, and a good liner dynamic range for quantitation because of the way it detects ions. Both the Thermo LTQ and the Agilent Q-TOF are outstanding instruments, but in (my opinion) very different ways.

If you are looking at mass accuracy as being an important factor, you may also want to look at the new Waters Q-Tof that uses an ion mobility spectrometer as a front end. This instrument is specifically designed for peptide analyses, although it has many other applications. Applied Biosystems (MDS/Sciex) also has a good Q-Tof as does Bruker Daltons). Both of these instruments are like the other Q-TOF instruments in that they will provide MS/MS and good mass accuracy. Another possibility that allows for mass accuracy and MSn is the Shimadzu ESI QIT-TOF.

But back to my original question, Could you explain how you have put these two instruments in the same category?

[gckiv]

I'm not trying to compare apples and oranges. I'm trying to compare user experience for similar applications on both an apple and on an orange to help decide between a linear trap and a Q-TOF. We're leaning toward the Q-TOF because mass accuracy and resolution is more important than MSn capability. But I was curious as to the general performance of the LTQ. That's why I was asking. Do you have any experience with Agilent's Q-TOF? I know they had struggled to be a key player in the game over the last few years, but I'm hearing better and better things regarding their MS instruments. We're also looking into the Bruker, Applied Biosystems, and Waters / MicroMass units. Thanks.

[Kostas Petritis]

Gckiv,

I think that if you are ready to sacrifice some cycle time for high mass accuracy (and as you are not doing proteomics probably you do not care about cycle time too much) then the Agilent Q-ToF is probably the instrument for you.

The Agilent Q-TOF seem to have better cycle times (i.e. 5 MS/MS spectra than the competitors) and better mass accuracies.

I do not know really about sensitivity but this is something you could figure out from the specs of each instrument... You should also have a look in their software as it must be quite new so you never know...

I also do not agree much with David's opinion on the orange to apple comparison when it comes to proteomic applications but I won't elaborate more on this forum...

[gckiv]

We've decided that we're going with a Q-TOF. We've talked to Agilent and ABI, and we're meeting with Waters today. We're also going to look into the Bruker micrOTOF-Q. Does anyone have any opinions on any of these?

We're interested in the best bang for our buck for mass resolution and accuracy at the high end (~150KDa), intuitive user interface and capabilities, calibration efficiency, audit trail features (we're in a regulated environment), good reporting capability (to make nice, concise reports for non-technical reviewers), and a simple, reliable method for MW and MS/MS database searching and reporting for peptide mapping. We're usually analyzing pure proteins, peptides and oligos and comparing them to our reference standards for release testing of pre-clinical/Phase I clinical trial therapeutics. Any input would be much appreciated.

[MS made easy]

You didn't mention reliability. At Pittcon last week Agilent announced they had sold 25 QTOF's worldwide but did not comment on delivery. Seems like not that many to stake your QC on.

[james little]

We have a GCT and a LCT from Waters and somewhat old now. When acquiring accurate mass on both of these instruments, one has to be fairly careful when acquiring and calibrating. They are both TDC type detectors which means one must deal with dead time correction. I am sure they have probably improved the situation significantly in newer instrumentation, but worth asking them about this issue.

I think the Agilent and the JEOL instruments are ADC type detectors which don't have dead time issues. JEOL talks about the advantages and disadvantages of TDC and ADC detectors at

http://www.jeol.se/JEOL%20News/news28A/ ... index.html

We have some information about our experiences with our GCT and LCT type data in the accurate mass section at

http://users.chartertn.net/slittle/

Let me know which one you decide to buy and why if you buy a QTof. I would like to buy one for our labs and your information would be useful to me.

Good Luck..