Comparative identification of irradiated herbs by the methods of electron paramagnetic resonance and thermoluminescence

Non irradiated and gamma-irradiated dry herbs savoury (Savoury), wild thyme (Thymus serpollorium) and marjoram (Origanum) with absorbed dose of 8 kGy have been investigated by the methods of elecrtron paramagnetic resonance ( EPR) and thermoluminescence (TL). Non-irradiated herbs exhibit only one wea k siglet EPR signal whereas in irradiated samples its intensity increase an d in addition two satelite lines are recorded. This triplet EPR spectrum is attributed to cellulose free radical generated by irradiation. It has been found that upon keeping the samples under the normal stock conditions the life-time of the cellulose free radical in the examined samples is similar to 60-80 days. Thus the conclusion has been made that the presence of the E PR signal of cellulose free radical is unambiguous indication that the samp le under study has been irradiated but its absence can not be considered as the opposite evidence. In the case when EPR signal was absent the method o f TL has been used to give the final decision about the previous radiation treatment of the sample. (C) 1998 Elsevier Science B.V. All rights reserved .