Elucidation of peptide metabolism by on-line immunoaffinity liquid chromatography mass spectrometry

An immunoaffinity chromatography extraction capillary liquid chromatography separation has been coupled to electrospray ionization mass spectrometry for on-line characterization of drug metabolites of a therapeutic peptide in plasma. It is demonstrated that the selectivity, sensitivity and molecular weight data provided by immunoaffinity chromatography coupled to liquid chromatography/mass spectrometry provides a means of rapidly achieving qualitative determinations of small amounts of material in complicated biological matrices such as plasma. The ability to detect the peptide in rat plasma at a level of 10 ng/mL is demonstrated using this method. In addition, experiments to study the epitope of the peptide by enzymatic digestion and mass spectrometry are also discussed. The method is proposed as an alternative approach to studying the metabolism of therapeutic peptides.