Atypical Chromatogram

Hello, we have observed a couple of atypical chromatograms in the same run.  In a run sample injections, the 11th and 13th injection were observed to be atypical.   We have looked into the parameters of each injection and they are within our method specifications, also the pressure has been constant throughout the sample injection.  Any advise or next steps to figure out what is happening would be really helpful.

Thank you all! :-)

  • Hello Jess,

    Is the blue your typical chromatogram and the red your atypical? 

    If yes, you have a few things I can say.  This must be a gradient run based on the baseline at the end of the run.  There appears to be a late eluting peak at ~9 mins since it's so broad and the peaks from ~5-8 mins are unresolved from what appears to be high organic content.  The last part from ~25 mins appears to match.  

    Not sure what SW you are using but in Agilent's, you can overlay the pressure traces with the chromatogram.  If you can and atypical chromatogram is different from a typical, then most likely causes would be check valves and/or the MCGV.

  • I agree with  that this issue seems to be restricted to the first couple of peaks. The rest of your chromatogram seems to match well. Overlaying the chromatograms would help with visualization. The MCGV could be the issue, as this would change the %organic in your system if it's not functioning properly. Another possible cause could be you sample. Is it being temperature controlled? Is it possible that the sample is degrading by the later injections?

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