Application of amino acid analysis using hydrophilic interaction liquid chromatography coupled with isotope dilution mass spectrometry for peptide and protein quantification

Amino acid analysis that is based on the use of hydrophilic interaction liquid chromatography (HILIC) coupled with isotope dilution mass spectrometry (IDMS) has been developed for the accurate quantification of underivatized amino acids from hydrolyzed protein/peptide. Sufficient separation of amino acids on a zwitterion chromatography (ZIC)-HILIC column was achieved after removal of chloride ions in the hydrolyzate. The detection limits and quantification limits as concentration of the four amino acids ranged from 0.003 to 0.04 pmol μL−1 and from 0.01 to 0.1 pmol μL−1, respectively. The analytical results for the certified reference materials, angiotensin I and bovine serum albumin (BSA), were satisfactory. Furthermore, the quantitative results by this method were compared with those by the commercially available precolumn method, derivatizd with aminoquinolylhydroxysuccinimidyl carbamate (AQC method), and better recovery and more precise data were obtained with this method.