Estimation of Irradiation Doses of Raw Beef Liver Samples using 5,6-Dihydrothymidine as an Irradiation Marker

摘要

The quantities of (5S)- and (5R)-5,6-dihydrothymidine (total DHdThd) in frozen beef liver samples were compared between those irradiated by an electron beam (EB) and those subjected to γ-irradiation. DNA extracted from the samples was enzymatically digested to nucleosides and analyzed by liquid chromatography–tandem mass spectrometry for total DHdThd and 2′-deoxythymidine (dThd). Total DHdThd was formed radiospecifically and dose-dependently and the dose–response curves of the ratio of total DHdThd to dThd (total DHdThd/dThd) were similar for both the EB- and γ-irradiated samples. The total DHdThd/dThd was stable after long-term storage (4 months) at ?20 °C and the followed heat treatment in a microwave oven. The total DHdThd/dThd could be a robust marker and is equally effective at quantitating both EB- and γ-ray irradiation history. The irradiation doses of raw beef liver samples were estimated using the dose–response curves of the total DHdThd/dThd of other irradiated samples. The ratio of the estimated dose to the actual dose was 0.74–1.30 in the irradiation range of 4.67–7.62 kGy.