Additional peak in chromatogram

<p>I'm having issues with an additional peak sometimes (not always) appearing in my reference sample chromatogram.  The peak is alwasy at ~160 mins and is a sharp disctinct peak.  Before the reference sample is injected a waters MassPREP peptide mix vial (186002338 -contains a mix of 10 peptides) reconstituted in 0.05% TFA in water is injected onto the system followed by an injection of 1% solvent B. (Line A1 = 0.05% TFA water and B1 = 0.04% TFA in acetonitrile run over 240 mins using a gradient curve of 6. The column is a BEH C18 with a guard column attached).  The reference and samples are prepared in NH4HCO3 solution.</p><p>The additional peak is never present in the sample chromatograms or contamination check (half sample/half reference).  Is this carryover contamination from the MassPREP injection?  Any ideas what else this could be?  </p>


  • fazal

    Please choose at least 6 chromatograms containing unknown Peak .calculate %rsd and Tell me the Result please.

  • Do you already have measured with MS detection? From the mass you will gain more information if this "impurity" is peptide related or not.

  • TG

    To see if the peak has a relation with the injected sampple it can be handy to duble teh injection volume.

    If the area is also increasing it is somting friom your injected sample. (cary over is than excluded)

    Injecting no (zerro) volume can help to see systempeaks.