Missing qTOF Reference Ions

Hello,

 

I am not seeing all of the reference ions (negative or positive) while my qTOF instrument is in idle or acquisition.  Spectrum and Work List icons remain yellow whereas Vial icon remains red. A fresh reference solution was prepared, flow and function of nebulizer confirmed. Some additional details as follows:

 

  • In negative mode, seeing only 112 and 1033 m/z.  Not seeing 119, 301, 966, 980, 1633 m/z.  Similar scenario in positive mode; seeing only 121 and 922 m/z.
  • Played with MP flow rate, reference nebulizer pressure and other parameters to no avail.
  • I have a dual ESI source.  Set up for small molecule analysis; 1700 m/z, 2 GHz.
  • Instrument recently passed calibration and tune for TOF and Quad.
  • Acquisition software recently upgraded to Version 10.  Methinks this is the culprit..?

 

Best regards,

Mark

Parents
  • Conclusion:  The nebulizer is ineffective for delivery of reference ion solution to the source.  Apparently this is the case for at least one other user of the 6350 instrument and I suspect there are more out there.  The work around includes configuring an isocratic pump and a splitter to deliver ref ion solution via a T post column.  The pressure of the isocratic must slightly exceed (~2-3 bar) pressure of HPLC pump; this gets fun when you're running a gradient!  Not perfect and will require more futzing.

     

    Addendum:  TFA should be eliminated from the tuning mix since it functions as an ionization suppressor.  

Reply
  • Conclusion:  The nebulizer is ineffective for delivery of reference ion solution to the source.  Apparently this is the case for at least one other user of the 6350 instrument and I suspect there are more out there.  The work around includes configuring an isocratic pump and a splitter to deliver ref ion solution via a T post column.  The pressure of the isocratic must slightly exceed (~2-3 bar) pressure of HPLC pump; this gets fun when you're running a gradient!  Not perfect and will require more futzing.

     

    Addendum:  TFA should be eliminated from the tuning mix since it functions as an ionization suppressor.  

Children
  • Thanks for all the feedback...

     

    Mitch

  • Hey Mark, 

     

    You likely have too much restriction in the long PEEK tubing the comes from the reference bottle to the reference nebulizer. Deposits can accumulate over time and cause too much restriction. The CDS (calibrant delivery system) functions with set backpressure, so if the restriction increases the flow will decrease. 

     

    If your FSE has already flushed this with hot water and organic, I would place another service call and have the line replaced and flow verified. The on-board CDS should be sufficient for delivering reference flow. The major drawback of the system is the small bottle volume means that you need to refill it often. 

     

    I agree that the isocratic pump is a superior solution. Rather than Teeing in post column, I would run it to your reference nebulizer with a passive splitter and recirculate the split volume back up to the bottle of reference solution. I have several customers running this setup successfully. 

     

    This kit was originally purposed for CE-MS, but works well in this application. 

    https://www.agilent.com/cs/library/usermanuals/public/G1600-90117.pdf 

     

    Best wishes, 

    Ryan

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