Peak Tailing - Machine Related??????

<p>Hi,</p><p></p><p>I'm currently developing a method for a small molecule.</p><p></p><p>Started development on our i-class (FTN) and almost immediatley got a good looking peak.  Brought the run time down to 1.2 mins.  Peak tailing was around 1.3 which I was very happy about it.</p><p></p><p>Due to some scheduling issues I moved the semi-developed method onto our other i-class system.  system exactley the same as the previous one.  Same column and mobile phase.  Tail factor now at 1.9!!</p><p></p><p>Can't figure out what is causing this change??</p><p></p><p>Looked at fittings.  they seem fine.  Made sure the purge and wash solutions are all correct and primed as well.</p><p></p><p>Could there be a sytem related issue causing this?</p><p></p><p>I moved the method back to the original machine and peak shape is back to how it was.</p>

Comments

  • Two different same systems can give you such difference.

    We have two different UPLCs, old one and new one, they give us different resolution for four different amino acids.

  • Your observations indicate that something is different between the two systems.  This is not likely to be a result of system variance but a subtle difference in plumbing or operating conditions.

    Since peak tailing is your concern, I'd be focusing my attention on anything the sample passes through.

    Injector -- needle, needle seal.

    Did you try calibrating the needle seal ?

    Active Preheater -- look carefully to see if the PEEK ferrule on the "offending" system is compressed.  If in doubt, replace with a new one.  Make sure both systems are using the preheater the same way.  It is possible to disable it via the Console.

    PEEK tubing connecting column outlet to detector -- look carefully at ends of tubing to make sure the cut is square and the end is not flared (the result of long term use and overtightening).  If in doubt, dress the ends (clip) or replace.

    I assume you are using an optical detector (TUV or PDA).  Make sure the flow cells are the same.  There are different flow cells available for the different ACQUITY platforms (HClass & Classic ACQUITY/IClass).  Distinguishing between the 2 will require you to remove the flow cells from the detector body and look at the tubing attached to the flow cell.

    If you are still struggling -- contact your local Waters representative.  These are the kind of things that are very important to us and their subtlety may require a trained eye.

    Good luck,

    Rich

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