Abstract: Ultra performance liquid chromatography-quadrupole linear ion trap mass spectrometry (QTRAP-UPLC-MS/MS) was employed to determine several amino acids and their isomers formed upon irradiation of seafood and the effect of irradiation dose (0.5–20 kGy) on the contents of m-tyrosine and o-tyrosine as irradiation markers in different seafood products was studied. Also, this study investigated the effect of storage conditions and processing methods on the specificity and stability of m-tyrosine and o-tyrosine as well as on the detection of irradiation seafood. Our results showed that phenylalanine could be converted to p-tyrosine, m-tyrosine and o-tyrosine by irradiation without microorganism or enzyme, which was linearly related to irradiation dose. Furthermore, the irradiation dose and moisture content were closely related to the production of m-tyrosine and o-tyrosine, which had good stability at ?20 ℃. Different storage conditions and processing methods had certain effects on the contents of m-tyrosine and o-tyrosine in irradiated seafood; however, the amounts of extracted m-tyrosine and o-tyrosine were sufficient for identification of irradiated seafood. The QTRAP-UPLC-MS/MS method with m-tyrosine and o-tyrosine as markers could precisely identify irradiated seafood with a dose as low as 0.5 kGy, and provide the basis for food safety monitoring.

Key words: ultra performance liquid chromatography-quadrupole linear ion trap tadem mass spectrometry (QTRAP-UPLC-MS/MS), irradiated seafood, phenylalanine, m-tyrosine, o-tyrosine