direct infusion fragment spectrum LC-MS/MS


Has anyone generated a fragmentation spectrum using an Agilent QQQ (e.g., G6420A) using direct infusion?  I am accustomed to making a solution of an analyte and then infusing it directly into the ESI source using a syringe infusion pump at low flow rate (10 uL/min).  I would set the Q1 to the analyte exact mass and the Q3 to scan and then adjust the ESI source and Q2 parameters (collision energy) as the mass spec was running to generate an fragment spectrum.

  • Achem,

    You are describing a Product ion scan method in which MS1 is set to TTI (all ions allowed to pass), CC has some CE applied, and MS2 is set to scan across a defined m/z range. This can be selected as an acquisition mode in the software QQQ UI.

    If you know the precursor ion m/z, you can do this via MassHunter Acquisition software by modifying the CE in the acquisition method and monitoring via the spectrum plot. The data files will not be saved unless you run sample through the software. 

    The syringe pump will be controlled out of the MH software.

  • Thank you mipastor!  You are correct I am trying to conduct a product ion scan with MS1 set to dwell on the precursor ion m/z so sounds like I should use mass hunter.  I was thinking of just getting a stand alone syringe infusion pump with a gas tight Hamilton syringe and connecting directly to the ESI infusion needle with peek tubing instead of flow from LC system, would you anticipate any problems with this set up?

  • If you decide to direct the flow from the syringe pump directly to the nebulizer and not the standard port on the MS diverter valve, you will not be able to use the diverter valve to change from LC flow > nebulizer to LC flow> waste or use the Calibrant Delivery System (CDS) within the MH software. No other issues or problems I would anticipate. 

    This assumes you will remove the standard CDS peek tubing that normally goes to the nebulizer and instead use the peek tubing from the syringe pump. 

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