A simple,rapid and accurate method for the determination of hydroxyproline in collagenous proteins by high performance liquid chromatography-electrospray mass spectrometry(HPLC-ESI/MS)was developed.After hydrolysis of collagenous proteins with hydrochloric acid,the hydroxyproline was separated on a Spherigel C8 column using acetonitrile-0.05% trifluoroacetic acid aqueous solution(5∶95,v/v)at a flow rate of 1.0 mL/min.Theanine was used as the internal standard for the quantification.Hydroxyproline was identi...