Ammonium Formate mobile phase

MikeT

<p>Greetings</p><p></p><p><span style="font-size: 10pt; font-family: arial,helvetica,sans-serif; ">I have maybe stupid question but I don't assume anything.</span></p><p><span style="font-size: 10pt; font-family: arial,helvetica,sans-serif; "> </span></p><p><span style="font-size: 10pt; font-family: arial,helvetica,sans-serif; ">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.</span></p><p><span style="font-size: 10pt; font-family: arial,helvetica,sans-serif; "> </span></p><p><span style="font-size: 10pt; font-family: arial,helvetica,sans-serif; ">Is formic acid used to pH to ph3.0?</span></p><p><span style="font-size: 10pt; font-family: arial,helvetica,sans-serif; "> </span></p><p><span style="font-size: 10pt; font-family: arial,helvetica,sans-serif; ">Is it approved to use on the TQD?<span id="_marker"> </span></span></p><p><span style="font-size: 10pt; font-family: arial,helvetica,sans-serif; "><span> </span></span></p><p><span style="font-size: 10pt; font-family: arial,helvetica,sans-serif; "><span>TIA</span></span></p><p><span style="font-size: 10pt; font-family: arial,helvetica,sans-serif; "><span> </span></span></p><p><span style="font-size: 10pt; font-family: arial,helvetica,sans-serif; "><span>Mike</span></span></p>

LNE33

Hi Mike,

In our lab we use this:

http://www.fishersci.com/ecomm/servlet/fsproductdetail?storeId=10652&productId=786018&catalogId=29104&matchedCatNo=A666500&endecaSearchQuery=%23store%3DScientific%23N%3D0%23rpp%3D15&fromSearch=1&searchKey=formate||ammonium&highlightProductsItemsFlag=Y

We use formic acid to adjust pH (ammonium hydroxide if your pH dips too low), though we haven't gone as low as 3.0.

If you have to use more than 2 mL of formic acid to adjust 1 liter of mobile phase, I might be a bit nervous to run this into the TQD - your sensitivity could start to drop due to the amount of formic acid. I've heard of some assays using up to 0.5% formic acid mobile phases, though.

Good luck,

Laura

RD

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.