apci tuning issue

Hi We have an APCI on our 6120 MS. 

Thanks to Dannymobbs we cleaned the capillary and put it in. Negative tuning is coming out but the positive is showing a high steady peak over a wide range of m/z. Not a peak but suddenly increases at the target m/z then stays up high until the end of the m/z range (looks like a cliff). Any suggestion on this symptom?

Also I was concerning that when we previously had issues with the tuning (no peak or signal but noise came out), we kept tuning and the system recommended doing some peak width, axis calibration checks. I was wondering if this could have altered the tuning parameters (when no peak was there) but now even if we have peaks, it's not tuning properly because of the interrupted parameters? I would appreciate any advice! Thank you.

  • Hi Anme,

    Have cleaned or replaced the corona needle? Do you have a last known "passing" tune in APCI? If you do, you can load those values, save the tune and try autotune again, BTW, make sure that corona needle is clean and you have good spray.



  • Hi Mitch

    Yes corona needle was recently replaced, cleaned daily before MS analysis.

    I looked at some previous values, the main difference was the width gain, which was a negative value in the bad tuning case (attached positive tuning report below). Negative tuning was fine.

    Also, the nebulizer spray seems okay to me when I pull it out and let solvent go through. I see drops with 4-5 seconds, and when turned on, a continuous spray with a conical shape. BTW. Can nebulizer needle replacement cause this issue? Like the connection between ferrules or something I did wrong during the replacement?



  • Hi,

    Yes a improperly installed needle can cause an issue with tune. Have you looked at spray by removing the nebulizer and observing the spary?



  • Yes I did - continuous spray with a conical shape. But is there another way to check this, although it seems visually okay?

  • Sorry for the delay. Have you tried putting ESI source and checking tune for that? Looking at the pictures might point to an electronic issue.

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