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Gain Factor Constantly Out of Tolerance for Check Tune

K_Ruiter

I am running on an Infinity 1260 II Ultivo LC/QQQ and have a problem when running check tunes. Every time I run a check tune, I get an out of tolerance result where the only parameter out of range is the gain factor. It fluctuates between being out of range on the low end (0.6 or 0.7) and the high range (1.3 to 1.5), it is not consistently too low or too high. I am having to constantly autotune the QQQ which takes longer to do. The autotune will pass with a gain factor of 1.0, and then check tune the next day will fail due to gain factor. 

Has anyone seen an issue with gain factor values? Is there any specific part of the mass spec that the gain factor is associated with that may need attention (maintenace, cleaning, replacement etc.)? Any input would be appreciated.

  • 0

    The tolerances for the gain check are not well defined to users in MH. 

    The gain (similar to EMV/delta EMV) is determined through an autotune. By definition, this gain or EMV is set at a gain of 1.0. This is the EMV/gain to be used for data collection. A gain table is created from a minimum value of 0.1 up to a maximum value of 10.0. If the EM horn is aging, the gain table will be truncated (not able to achieve a maximum gain value of 10.0). This is ok, but may suggest need to replace EM horn (EMV approaches maximum value). 

    As part of a chacktune, the gain is "checked" to see if it is close to the original gain of 1.0 determined through the most recent autotune. Ideally, this measured gain should be close to 1.0. The tolerances are 1.0 +/- 0.25 (0.75 to 1.25). If the measure gain is outside of this window, the result of the checktune will be "out of tolerance". 

    A potential way to resolve this would be to perform a new autotune (gain of 1.0 is set) followed by a checktune (measured gain should be close to 1.0). Obviously, there are multiple factors that may be contributing here. 

  • 0

    Hello,

    Did you resolve your problem because I am having a similar problem with a 6490QQQ.  Each time the system either autotune or I run check tune, masses are out of tolerance, especially in MS2.  There has been many things tried by the engineers, but nothing has fixed the problem.  Any assistance would be appreciated.

  • 0 in reply to dawn.harrison

    Hi Dawn, unfortunately I am still having issues. My only guess for my scenario is that it is an EM issue with the gain factor always changing when doing check tune. I cannot think of why else the gain factor is in range when an auto tune is done, but fails for check tunes the next day.

    For your situation, I believe the only time we had issues with masses out of tolerance was after changing the ion injector. When we put a new ion injector in, we could not get tunes to pass. We had to put back in our original ion injector after cleaning it to get tunes to pass. I hope you can find a solution!

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