Analysis of the endogenous human serum peptides by on-line extraction with restricted-access material and HPLC-MS/MS identification.

The selective extraction of endogenous serum peptides has been a challenge due to the high abundant proteins present in serum. Here a simple on-line extraction of peptides from human serum using strong cation-exchange diol silica restricted-access materials (SCX-RAM) coupled with two-dimensional RP-RP liquid chromatography mass spectrometry was developed. The operation of the on-line extraction system is simple to use and does not need complex equipments. The two-dimensional RP-RP was proved to be orthogonal and efficient to separate peptides extracted from human serum.