Loss of signal after use of different mobile phase on UPLC-MS/MS

<p>I am currently running a method on our UPLC - Quattro Premier XE system with the following characteristics:</p><p></p><p>Flow 0,3 ml of 0,1% formic acid/MeOH with a 4 min gradient using line A1 & B1. We are making use of the column manager.</p><p></p><p>Now the following happened a few weeks ago:</p><p></p><p>My colleague run his method with a flow of 0,3 ml of 10 mM NH4HCO3 pH10 using line A2 & B2 and had great results</p><p></p><p>After this I ran my method again and had a loss of signal of appr. 70% when compared with the results I was used to.  Throughout the last weeks this turned out to be a very reproducible situation. His method with good results and my method with this enormous loss of signal when I ran my method after his method. Only after very extensive washing with 100% MeOH I got my high signals back. </p><p></p><p>Now is my colleague's method a new one and I thought at first that the MS-part of the system was contaminated. Until recently. It was on one of my runs where I had high signals that I interrupted my series and primed the UPLC for 4 minutes with my colleague's mobile phase, the NH4HCO3 mobile phase so that he could run his samples directly after mine. Just priming, nothing more. Now I restarted my run and again had this loss of 70% of signal. And it stayed low until the end of my run. Now, during priming there is nothing going towards the mass spec so this must be a UPLC related issue. What is going on here?</p><p></p><p>Is there anyone out there who knows what the problem is? Any suggestions? Would like to hear from you guys.</p><p></p><p>Thanks you all.</p><p></p><p>Bertrand van Zelst</p><p>Erasmus Medical Center, Rotterdam, the Netherlands</p>


  • lizh


    Did you use the same column for both methods?

    Note you are switching from low pH to high pH



  • Hi Liz,

    Different columns.

    We are aware of the pH difference, but just priming the A2 line and resuming my run, I find it hard to imagine that just priming has that much of an influence.

    Best wishes,