Electron Spins Resonance (ESR) Spectrometry: Dose Assessment And Detection Of Irradiated Dates (Phonex Dactilifera L.)

The present study dealt with the use of electron paramagnetic resonance (ESR) spectroscopy to distinguish between irradiated and non-irradiated date (even after long storage period) and estimation of the initial absorbed doses. Also, the aim of this investigation included determination of the minimum detection limit of absorbed dose. The assessment of initial absorbed doses was carried out immediately after irradiation, after 7, 15, 30 and 60 days by using calibration curve method. Date samples were tested for their ESR signal intensities. ESR technique was successful for identifying both irradiated and non-irradiated samples by spectrum profile (shape and characteristics of ESR signals). The minimum detectable absorbed dose was found to be 0.5 kGy and the decay percentage during the entire post-irradiation storage was found to be 50.49 %, therefore, the corrections for decay in calibration curve methods were introduced. The present study suggested an alternative approach in which a standard calibration curve constructed after 60 days (when ESR signal or free radicals in the irradiated samples have reached stability) was used to estimate the irradiation doses absorbed by the sample. The evaluated doses obtained by this approach were almost near the ones obtained by using correction for decay of free radicals. Also, the present study aimed to activate or enhance the decayed ESR signal at long storage period as in case of long storage of dry date. Using 95% ethanol treatment and re-irradiation with low dose (3x10^-5 kGy) were more effective methods to distinguish between the irradiated samples in spite of weakness ESR signals after 18 months of storage. It could be concluded that ethanol treatment or re-irradiation with low dose for long stored date samples improve the detection ability using electron spin resonance (ESR).