Peak Splitting

RHuber
RHuber
in Instrumentation and Mass Spectrometry
<p><span>Hello, </span></p><p><span>I am having the issue of splitting peaks in a method for testing estrogen compounds. I am using the following method:</span></p><p></p><p><span>Column: 2.1X50mm BEH C18</span></p><p><span>Temp: 40C </span></p><p><span>Mobile Phase: Acetonitrile:Water 50:50</span></p><p><span>Flow: 0.75 mL/min</span></p><p><span>Pressure: <11,000 psi</span></p><p><span>Inj. : full loop (10uL)</span></p><p><span>Detection: PDA 205nm</span></p><p></p><p><span>I am seeing splitting occur after about 250 inj. I also tried a lower injection volume, but this did not help. The sample diluent is 0.9% saline and the highest sample concentration is 5ppm.</span></p><p></p><p><span>Any suggestions on the cause of the split peaks? I had a similar issue with the same method when I was using a sample diluent of 25% ethanol / 5% propylene glycol and the columns were lasting ~800 inj before split peaks. I was told that the likely cause was the PG. Now I am just using a saline solution and the column is only lasting for 250 inj. </span></p><p></p><p><span>Thanks,</span></p><p><span>Rob</span></p>

Comments

  • dougm
    dougm

    Hello,

    On how many columns has this occurred? How long have you been running this method and has anything changed recently?

    Most importantly, have you contacted your local Chemistry Specialist?

    Thanks,

    --Doug

  • RHuber
    RHuber

    Doug,

    This is the first column with using this sample diluent. I went through 4 columns with the 25% EtOH / 5% PG diluent and was informed that the issues were likely the PG contaminating the column. This method is not at extreme pH, temp, or pressure, so I would not expect the columns to have issues with this few of injections.

    I have not contacted the local Chemistry specialist as I am not sure who this would be. (I am in central MI)

  • lizh
    lizh

    Hello:

    I would try a smaller injection. 10 uL seems a lot for a short column.

    The quickest is to go to PLNO - no loop change, though I always recommend FL just as you are using when developing a method. But here, choose a simple needle wash, as its isocratic you can use exactly the same 50/50 for the Weak and Strong needlewash, or whatever you are using right now - what is it.

    In the meantime I have asked some of our chemists to share a method I happen to know we are developing. I believe we had good success with HSS.

    Best regards,

    Liz

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