QTrap 5500 LC/MS/MS Tuning Variability

[IsotopeC12]

Hi,

Would anyone have any insight into the possible causes for obtaining two

significantly different MW tuning results between Mass Spec Instruments?

Say the MW I am looking for is 170
(using +1amu on both instruments with the same gas/temp levels..etc..)

also using the same infusion solution...

On one Mass Spec I can see 171

On the other Mass Spec I can only get 172...+2amu greater

I am thinking the second Mass Spec is out of calibration...but I am wondering if there could be any other causes..

[Gaetan Glauser]

Hello,

do you get a mass difference of exactly 1.0 Da between both QTrap? Are the signal to noise ratios equivalent?

Do you also get the difference in negative mode?

It seems that one of your machines is detune or has an electronic bug. Before you re-calibrate it, you can try to reboot the system.

[IsotopeC12]

This happens only for certain drugs now and then, sometimes it tunes good and then I will get something 2amu away when I am asking only for 1amu. If I take that same drug to another mass spec, I can get the 1amu. So I am wondering if it is a calibration issue...