Anyone out there has experience on separation of peptides. I need to development an LC/MS/MS assay on a peptide with the molecular weight around 700. I used 0.1% formic acid in water and methanol (gradient) and the column is Supelco discovery C8. However, I got a peak split or a peak with shoulder. How can I eliminate this problem?

Thank you very much.

Paul

There is no reason why a peptide should give you two peaks under the running conditions. It may very well be, that your peptide is not pure, even with the same MW. I assume that you have compared the two spectra?