Autotune Failed on Thermo MSQ ElMO

[danicrd]

I'd like to know if anyone are using Thermo MSQ coupled with dionex IC..We have one and everyday is a battle.
The system is very irreproducible and sensitivity is low.
I have tried a full system autotune but has failed. High masses are very low, but if i make a scans with calibrant solution i'm able to see m/z 1972.
I have already cleaned cone and rf hexapole
Someone has never tuned instruments successfull?
Any help is very appreciated

Thank you

[shikingb]

The MSQ may not require AutoTune if it is mass calibrated. Check mass calibration with a known standard. If your are using a dionex IC and are running anions for example, you could run a Chloride standard with an appropriate full scan (eg 20 - 120 Daltons) and then review the resulting mass spectra. If the MSQ measures m/z 35 & 37 +/- 0.2 Daltons, you are well with the specificiation of mass accuracy for the MSQ - thus AutoTune is not necessary.

AutoTune can fail for a variety of reasons but one of the most common problems is due to impurities that compete with the Calmix ions used when running AutoTune. Make sure you use new Calmix and freshly made, degassed, mobile phase.

[danicrd]

thank you for reply
The system is out of tune, because m/z 69 (chlorite) is read at 68.7 (i've tried direct infusion of solution). Pheraps the tune software display an error "no valid calibration"
The calmix was fresh and mobile fase also: now I have bypassed problem using m/z 68.9 in acquisition channel instead of 69 but I don't like this way...

[Csaba]

Hi,
Yes, we have had problems with tuning on MSQ (not ELMO).

The problem is that Xcalibur tune starts with the highest mass with weak signals. The instrument must be very clean then. (A clever tune program would start with the strongest signals. Dionex can't do anything about this, it is Thermo that are responsible for Xcalibur and the calibration solutions.)

An alternative to clean the intrument is dangerous and not really recommeded: Calibrate over a smaller span, if high mass range is not used. This can be done by editing the calibration file ( =removing the highest and weekest mass entries from it.)

[lmh]

I'm not familiar with the MSQ, only using Thermo's ion trap MS systems, but I assume they use the same cali mix.

If so, does the protocol ask you to tune to caffeine 195 before running the calibration? If so, try tuning to MRFA instead. If the system is allowed to maximise ion transmission for its lowest calibration mass, it often loses the high masses, so calibration fails. We changed our protocol internally to use MRFA ages ago, and subsequently found the engineers are doing the same thing when they check ion trap instruments.

[danicrd]

dear csaba thank you for reply. Where can I find calibration file?

[shikingb]

Chlorite [ClO2]- has two naturally occuring isotopes that occur at m/z 68.96 (100%) & 66.96 (32%). You are using the ion measured by the MSQ at m/z 68.7 - the difference between measured and theoretical is 0.26.

The actual mass accuracy spec for the MSQ is +/- 0.3 Daltons. Running and passing AutoTune may not deliver a closer mass measurment. I think the instrument is usable in its current state. That's not to say there is another problem in that the MSQ fails AutoTune.

It also sounds like you are using SIM and you have adjusted the SIM mass to what the MSQ is actually measuring. This is a reasonable and defendable choice to make since the MSQ is performing within spec. The other path you could take would be to adjust the span of the SIM channel to a value large enough to include the difference from Theoretical:
Mass = 69 & span = 1 &the MSQ would measure 68.5 - 69.5. This set-up will reduce sensitivity - ideally we want a lower span but sometimes larger spans are chosen in order to make the method more forgiving to variation.

[danicrd]

Yes, I'm using SIM acquisition but the problem is due to error "no valid calibration" and a lower sensitivity compared to instr when was ok.
I like to tune instr to obtain a maximum sensitivity

[Csaba]

lmh: I wish the protocol for MSQ was like that, but no.

danicrd: I just remeber that when we had the calibration problem, we changed computer and updated to Xcalibur 2.0. And at the same time it was some change of calibration that we were not aware of, but we used an old calibration solution - which might have been erronous.)

So check that the name of the calibration solution matches your caibration file in C:\Xcalibur\cali\Ref (and some registry entry). The name of the calibration file on our MSQ is now "NaI-KI-CsI Standard". (I have no reference of the previous name since we also changed thecomputer, it was ALMOST the same.) You have a different file since you have ELMO. (In "NaI-KI-CsI Standard", the lowest mass is 172.88.)

With notepad, it is possible to edit the file, i e remove entries, but you have to know what you do. First of all save the original file under another name so you can revert.

[shikingb]

The no valid calibration may be due to the scan range being used. This kind of warning will occur if the scan range defined (full scan) extends beyond the calibrated mass range of the MSQ. For example on an MSQ Plus or Elmo, the lowest calibrated mass is Na+ (m/z 23) and if your mass range extends down below m/z 23 Xcalibur will display this warning. The MSQ will still be able to extrapolate a mass measurement that is acceptable but one should confirm it.

For any mass spectrometer, correcting a sensitivity problem must include evaluation of the following functional modules; ionization, mass extraction and transfer, mass filtering (includes mass calibration) and detection.

The most common problem area is the mass extraction and transfer - ie the entrance skimmer and rf transfer lens. Make sure the entrance cone is in perfect shape (ie clean and not damaged).

The next most common problem is ionization. Make sure the ESI capillary is not partially blocked, make sure you have enuf temp and N2 to fully desolvate creating gas phase ions, and make sure you have enuf needle voltage to ionize (generally in the 2.5 - 4 kV range).

The next most common problem is detection. Make sure the Electron Multiplier voltage is high enuf to deliver the required gain. If the EM voltage has not been increased recently, do so by 100 V and then evaluate results.

The least common problem is mass calibration. The MSQ can hold its mass calibration for greater than 1 year without issue - its very stable from this perspective. One way to check this variable is to select the mass for you analyte that's being measured. For example if the MSQ measures m/z 68.7 for Chlorite, then set the SIM mass to m/z 68.7 with a span of 0.5 and compare results with what was acceptable from the past. If the sensitivity does not imporve, the problem has nothing to do with mass calibration.

Other comments being made on this forum...
Editing the reference table may not apply. These actions are effective when dealing with a contamination ion that occurs within the search window of a calibration mass during AutoTune. Specifically, when addressing AutoTune failure due to high residuals. Editing the registry to calibrate over a smaller span is risky - just by virtue of being in the registry one could accidently alter a setting that would really mess things up. I do agree with the comment about Thermo being more cleaver with the AutoTune routine - search for low intensity ions is a problem if they can't be detected because of a sensitivity problem.

The MSQ does not use the same calmix as a Finnigan ion trap system. Do not try using MRFA