Ammonium Formate mobile phase

GreetingsI have maybe stupid question but I don't assume anything. We have an Acquity UPLC/TQD.   We are looking at the Targeted MRM screening method using TargetLynx.  It calls for 5mM Ammonium Formate, ph3.0.  I’ve never used that before.  Is it just the crystalline HCO2NH4?  Does it have to be Optima LCMS grade?  If I’m making it up in Optima LCMS grade water isn’t that good enough?  The Optima LCMS grade ammonium formate is rather expensive. Is formic acid used to pH to ph3.0? Is it approved to use on the TQD? TIA Mike

Best Answer


  • Ammonium Formate is routinely used for Mass Spectrometry applications.

    My recommendation for mobile phase reagents and additives is and has always been to obtain HPLC grade or LC/MS grade if available.  Yes, Fisher Optima is not inexpensive, but neither are the problems associated with mobile phase impurities. 

    Whatever you decide, make sure you store it properly in a dessicator as ammonium formate is very hygroscopic.

    I have attached some documents that discuss LCMS contamination, mobile phase purity and common background interferences. 

    I hope you find them useful.

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