A method for detecting irradiation histories of raw beef livers was developed by measuring 5,6-
dihydrothymidine (DHdThd) using liquid chromatography–tandem mass spectrometry (LC–MS/MS).
Liver DNA was extracted using phenol–chloroform extraction followed by precipitation in 50% ethanol.
DNA was then enzymatically digested and nucleosides were purified using an OASIS MCX column.
DHdThd and thymidine (dThd) contents of resulting test solutions were analyzed using LC–MS/MS.
DHdThd was detected specifically after c-irradiation. Concentration ratios of DHdThd to dThd in the test
solutions increased dose-dependently after irradiation at 1.0–11.3 kGy, which included the practical dose
for sterilization of 2–7 kGy. Dose–response curves from beef livers of individual animals almost overlapped.
Thus, this method is a candidate for the detection of irradiation histories of foods from which
DNA can be extracted.