Broad peak at the start of gradient

<p>hi all,</p><p></p><p>I have observed a broad peak at the start of all runs of recent. The mobile phase is as follows:</p><p></p><p>MPA 10% MeOH, 90% H20, 0.05 % TFA</p><p>MPA 90% MeOH, 10% H20, 0.05 % TFA</p><p></p><p>The gradient starts with A/B 80/20 and runs over 10 mins to A/B 50/50 and then back to A/B 80/20 re equilibrating for 10 mins.</p><p></p><p>This broad peak elutes between 1 and 1.5 mins monitoring with UV detection @ 240nm</p><p></p><p>Any thoughts? It is not compound related. </p>


  • Jason

    Do you use this mobile previously and see no peak? Anything else change associated with the peak's appearance?

    Is there any chance that you could attach a chromatogram (sounds like you have alreday run a blank) and further details on column, and sample diluent, injection method etc.

    Many TX


  • Hello,

    I see that you have a 10 minute re-equilibration hold (at initial conditions) at the end of the gradient.

    So, could you please run this simple experiment and report back your findings (inject mobile phase, blank, std, etc)?

    1) First, cut this re-equilibration time in half (change to 5 minutes) and observe the 'peak' size.

    2) Second, double the re-equilibration time (change it to 20 minutes) and report back your findings.