This work focuses on the separation of diethylpyrocarbonate-modified histidine-containing peptides by strong cation exchange (SCX) chromatography prior to mass spectrometric analysis. The decrease in positive charge of diethylpyrocarbonatetreated imidazole in histidine, masked by the incorporation of the carbethoxyl group, provides us with an opportunity to use SCX for separating diethylpyrocarbonate-modified histidine-containing peptides from the unmodified ones. In this report, the diethylpyrocarbonate-modified histidine-containing peptide is eluted faster than the untreated peptide. Furthermore, the carbethoxy group can be effectively removed to generate the unmodified imidazole in the histidine residue by neutral hydroxylamine.
