The presented work is to determine the mass fraction of angiotensinⅠ in solution by isotope dilution method,which is a pilot study organized by Consultative Committee for Amount of Substance.Firstly,the hydrolysis time and hydrochloric acid addition volume ratio were optimized and the degradation of natural and isotope labeled proline,valine,leucine and phenylalanine during the hydrolysis process were investigated.Secondly,the mass fractions of proline,valine,isoleucine and phenylalanine in the angiotensinⅠhydrolysis solution was determined employing isotope dilution method with their reference materials as standards.Finally,the angiotensinⅠ mass fraction and associated uncertainty were calculated according to the amino acid mass fraction obtained,which was(75.2±2.6) μg/g.It showed that the result obtained in this paper has good equivalence with the average.It can be concluded that the isotope dilution method for peptide quantification is accurate and is suitable for peptide reference materials production.
