Peak shape changing; peak heigh gradually decreased to a half

<p>Hi everybody!</p><p></p><p>The problem that we are having is that the peak width increased during the run resulting in a peak height that decreased from 0.6 to 0.3 Au. The areas are the same so by looking at the RSD everything is fine (RSD of areas is 0.6) but by looking at the overlays we see the problem.</p><p></p><p>3-4 week ago this same the instrument showed a shifting of retention time and the peak shape changed to show a big shoulder but an error message pointed at the degasser. We moved the column to another instrument with good results so we blamed on the degasser and called Waters. Waters rep came and changed the degasser. Now this is the first run after changing the degasser and the problem is similar to what we saw previously. For now I'm moving the column again to another system; assuming that the column is OK, can someone sugest something to start troubleshooting the instrument? where to look at?</p><p></p><p>Thanks a lot!</p>


  • Hi Deleon,

    From what I gather, your retention time has shifted on your original instrument and simultaneously your peak height has changed from 0.6 to 0.3 AU.  If the the change in peak shape is shows a large increase in tailing factor, I would suspect it is time to change your column.  If the change in peak shape is based solely on a broader peak width, it sounds like there may be a problem with the pump pressure.  Might want to check the initial pressure for the system as a starting point.

    Good Luck,


  • rune

    Hi Deleon

    Have you changed instrument method parameters ?  Could someone accidentally have changed something especially the Detector settings like sampling rate and filter time constant ?  Was the change you have seen sudden in the middle of a sample set or was the change observed with a new sample set ?

    best regards