Radiation-induced Electron Spin Resonance Signal Research Articles

Electron spin resonance (ESR) study on gamma irradiated some modern paper samples

In this work, we use paramagnetic defects induced by gamma radiation in some modern paper samples to determine their main dosimetric properties in the decontamination dose range (0.5–10 kGy) of ancient papers. Electron spin resonance (ESR) spectra of photo paper, cigarette paper, white paper napkin (napkin), cash register receipt, straw paper and white photocopy paper recorded before and after irradiation with gamma rays were reported. Photo paper, cigarette paper and napkin samples displayed the radiation-induced cellulose-like ESR signals well known from the literature on cellulose-containing foods. Cash register receipt, straw paper, and white photocopy paper are another set of samples where different ESR spectra were recorded. The ESR signals of these three paper samples were shown to originate from carbonate mineral filler grains. Inorganic mineral fillers are commonly used in paper manufacturing. The dose-response curves associated with the radiation-induced sharp ESR signals originating from the CaCO3 filler of the cash register receipt (g = 2.0027), the straw paper (g = 1.9995), and the white photocopy paper (g = 1.9996) were found to follow a single exponential saturation function. Despite the observed decreases with time in the signal intensities of cash register receipt and white photocopy paper, detectable ESR signals were obtained even 100 days after irradiation for them and straw paper. The radiation-induced free radicals responsible for the ESR spectrum of straw paper were more stable than those of cash register receipt and white photocopy paper. The results indicate that free radicals induced in mineral CaCO3 filler grains incorporated within papers have the potential to be used for application to retrospective ESR dosimetry in the range of 0.5–10 kGy.

ESR dosimetric properties of gamma irradiated different origin eyeglass samples

In the present research, mineral and organic origin eyeglasses (CR-39) were examined with respect to their potential application in the dosimetry of ionizing radiation by using electron spin resonance (ESR) technique. Before irradiation, organic and mineral origin eyeglasses did not exhibit any ESR signal. But they do produce radiation-induced ESR spectra after gamma irradiation. The variations of the radiation-induced resonance signals of organic and mineral origin eyeglasses with microwave power and modulation amplitude were investigated and the optimum spectrometer operating conditions were determined. The dose-response curves of the organic and mineral origin eyeglasses exposed to gamma radiations were found to be described well by a linear and single exponential saturation functions in the dose ranges of 0.1–10 and 0.05–10 kGy, respectively. For mineral eyeglasses this behavior was linear at lower doses (0.05–1 kGy). Despite the observed fading with time in the signal intensity, measurable ESR signals were obtained even 54 days after irradiation for organic origin eyeglass, while the corresponding value for the mineral eyeglass was 154 days. The study also showed that the thermal stability of the radiation-induced ESR signal of mineral eyeglass sample was higher than the signal of organic origin eyeglass.

Identification of X-ray irradiated walnuts by ESR spectroscopy

Samples of non-irradiated walnuts exhibit a single line with a g value of 2.0045 ± 0.0006. The irradiation process gives rise to “cellulose-like” Electron Spin Resonance (ESR) spectrum two lines symmetrical to the central line, at a distance of ca. 3 mT. Irradiation increases the central line and produces two satellite peaks (lines) with an amplitude growing with dose. The stability of the radiation-induced ESR signal at room temperature was studied from a quantitative point of view. The fading study and dose evaluation were pursued for a period of two years analyzing irradiated walnuts samples.The reported curves, describing the fading at different doses, differ only by a multiplicative factor and the attenuation factor (the ratio between the amplitude measured and the amplitude evaluated after irradiation) depends only on the time elapsed following treatment.

Detection and original dose assessment of egg powders subjected to gamma irradiation by using ESR technique

Abstract ESR (electron spin resonance) techniques were applied for detection and original dose estimation to radiation-processed egg powders. The un-irradiated (control) egg powders showed a single resonance line centered at g =2.0086±0.0005, 2.0081±0.0005, 2.0082±0.0005 (native signal) for yolk, white and whole egg, respectively. Irradiation induced at least one additional intense singlet overlapping to the control signal and caused a significant increase in signal intensity without any changes in spectral patterns. Responses of egg powders to different gamma radiation doses in the range 0–10 kGy were examined. The stability of the radiation-induced ESR signal of irradiated egg powders were investigated over a storage period of about 5 months. Additive reirradiation of the egg powders produces a reproducible dose response function, which can be used to assess the initial dose by back-extrapolation. The additive dose method gives an estimation of the original dose within ±12% at the end of the 720 h storage period.

ESR-Based Investigation of Radiation-Induced Free Radicals in Fresh Vegetables After Different Drying Treatments

Fresh vegetables, such as paprika, cucumber, and cabbage, were gamma-irradiated at 0, 2, and 5 kGy. Different pretreatments and selection of samples were compared to obtain improved electron spin resonance spectral features resulting in better detection of irradiation status. The non-irradiated samples exhibited a single central signal at about g0 = 2.007), whose intensity showed a significant increase upon irradiation. However, the irradiation also produced the typical electron spin resonance spectra of the radiation-specific cellulose radicals showing two side peaks (g1 = 2.023 and g2 = 1.986) with a mutual distance of 6 mT. The difference in electron spin resonance responses was observed while analyzing the different parts of the same vegetable. The flesh sample gave better spectral characteristics providing clear radiation-induced electron spin resonance signals. The effect of different drying pretreatments was also evident providing the comparable or improved results when using alcoholic-extraction as an alternative to the conventional freeze-drying technique.

Investigation of Different Factors Affecting the Electron Spin Resomance-based Characterization of Gamma-irradiated Fresh, White, and Red Ginseng

Fresh (raw roots), white (dried), and red (steamed-drid) ginseng samples were gamma-irradiated at 0 to 7 kGy. Electron spin resonance (ESR) technique was used to characterize the irradiation status of the samples, targeting the radiation-induced cellulose radicals after different sample pretreatments. All non-irradiated samples exhibited a single central signal (g=2.006), whose intensity showed significant increase upon irradiation. The ESR spectra from the radiation-induced cellulose radicals, with two side peaks (g=2.0201 and g=1.9851) equally spaced (±3 mT) from the central signal, were also observed in the irradiated samples. The core sample analyzed after alcoholic-extraction produced the best results for irradiated fresh ginseng samples. In the case of irradiated white and red ginseng samples, the central (natural) and radiation-induced (two-side peaks corresponding to cellulose radical) signal intensities showed little improvement on alcoholic-extraction. The water-washing step minimized the effect of Mn2+, but reduced the intensity of side peaks making them difficult to indentify. The effect of different origins was negligible, however harvesting year showed a clear effect on radiation-induced ESR signals.

Identification of irradiated rice noodles by electron spin resonance spectroscopy

Electron spin resonance (ESR) spectroscopy has been applied to the identification of the irradiation of a wide variety of foods. In this study, ESR was applied to identify irradiated rice noodles. A detailed ESR investigation of irradiated noodles was carried out in the dose range 0.5–3 kGy. The stability of the radiation-induced ESR signal at cold (−4 °C) and room (25 °C) temperatures was studied over a storage period of 24 weeks. Irradiated rice noodle samples exhibited a strong, symmetric doublet ESR signal centered at g = 2.0, whereas unirradiated noodle exhibited a very weak signal. The ESR signal intensity increased linearly with radiation dose ranging from 0.5 to 3 kGy. Keeping the samples at −4 °C and 25 °C for 24 weeks caused decreases of 50% and 90% in the ESR signal intensities, respectively. However, long-term decay data at room temperature showed that the ESR technique could be used to identify irradiated rice noodles up to 24 weeks following irradiation. ► Rice noodle could be confirmed for irradiation treatment using ESR spectroscopy. ► Storage temperature and period after irradiation cause fading of ESR signal. ► The qualitative analysis can be done within storage period of 24 weeks.

Identification and Characterization of Gamma‐Irradiated Dried Lentinus edodes Using ESR, SEM, and FTIR Analyses

A detailed electron spin resonance (ESR) analysis for different parts of gamma-irradiated (0 to 50 kGy) dried mushroom (Lentinus edodes) was conducted to identify radiation-induced signals. All studied mushroom parts except gills produced strong dose-dependent radiation-induced ESR signals particularly at about g = 2.0076, 20005, and 1.9911 demonstrating the generation of crystalline sugar radicals following irradiation. The intensity of these signals was highest in cap skin samples, followed by the cap core, stem skin, whole mushroom powder, and stem core samples, respectively. ESR-based identification was easily possible at 2 kGy or more using mushroom cap skin or cap core as samples. The radiation-induced ESR signals were found sensitive to thermal treatment showing the limitation of ESR-based detection in case of heat-processed samples. Scanning electron microscopy (SEM) showed micro-structural damage upon irradiation resulting decreased percentage of rehydration; however, no major alteration was observed through the Fourier transform infrared (FTIR) spectra. Irradiation changed the structural morphology; however, the main functional groups were stable against radiation treatment. Food irradiation can confirm hygienic quality and prolong the product shelf life. However, due to lack of international consensus, effective identification methods and detailed quality characterization are required for the general use of this technology.

ESR and TL studies of irradiated Anatolian laurel leaf (Laurus nobilis L.)

Laurel leaf (Laurus nobilis L.) samples that originated from Turkey were analyzed by electron spin resonance (ESR) and thermoluminescence (TL) techniques before and after γ-irradiation. Unirradiated (control) laurel leaf samples exhibit a weak ESR singlet centered at g=2.0020. Besides this central signal were two weak satellite signals situated about 3 mT left and right to it in radiation-induced spectra. The dose–response curve of the radiation-induced ESR signal at g=2.0187 (the left satellite signal) was found to be described well by a power function. Variation of the left satellite ESR signal intensity of irradiated samples at room temperature with time in a long term showed that cellulosic free radicals responsible for the ESR spectrum of laurel leaves were not stable but detectable even after 100 days. Annealing studies at four different temperatures were used to determine the kinetic behavior and activation energy of the radiation-induced cellulosic free radicals responsible from the left satellite signal (g=2.0187) in laurel leaves. TL measurements of the polymineral dust isolated from the laurel leaf samples allowed distinguishing between irradiated and unirradiated samples.

ESR dating of calcrete nodules from Bala, Ankara (Turkey): Preliminary results

The age of two calcrete nodules (C1 and C2) from the Bala section in the region of Ankara, Turkey, is determined by the Electron Spin Resonance (ESR) method. Three radiation-induced ESR signals at g=2.0056 (A signal), g=2.0006 (C signal) and g=2.0038 (broad signal, BL) were observed. The broad signal (BL) intensity was used as a dating signal. The properties of this dating signal are described in this manuscript. The calcrete nodules were irradiated with a (60)Co gamma source and measured with an ESR spectrometer (X-band) to obtain the signal intensity vs. dose curve and fitted well with the single exponential saturation functions. Based on this model, accumulated dose (D(E)) values for dating are obtained using the multiple-aliquot additive dose method. The D(E) values of C1 and C2 calcretes are 1880±207 and 671±67 Gy, respectively. The ESR ages of the two calcrete samples are obtained by assessing the annual dose rate (D) from the content of (238)U, (232)Th and K(2)O determined by wavelength dispersive X-ray fluorescence (XRF) spectrometry. The results are 761±120 and 419±64 ka, respectively, falling into the Middle Pleistocene Epoch in the geological time scale in agreement with the positions of the stratigraphical record.

Identification of irradiated sage tea ( Salvia officinalis L.) by ESR spectroscopy

The use of electron spin resonance (ESR) spectroscopy to accurately distinguish irradiated from unirradiated sage tea was examined. Before irradiation, sage tea samples exhibit one asymmetric singlet ESR signal centered at g=2.0037. Besides this central signal, two weak satellite signals situated about 3 mT left and right to it in radiation-induced spectra. Irradiation with increasing doses caused a significant increase in radiation-induced ESR signal intensity at g=2.0265 (the left satellite signal) and this increase was found to be explained by a polynomial varying function. The stability of that radiation-induced ESR signal at room temperature was studied over a storage period of 9 months. Also, the kinetic of signal at g=2.0265 was studied in detail over a temperature range 313–353 K by annealing samples at different temperatures for various times.

Detection of γ-Irradiated Sesame Seeds before and after Roasting by Analyzing Photostimulated Luminescence, Thermoluminescence, and Electron Spin Resonance

Sesame seeds were irradiated using a (60)Co irradiator (0-4 kGy) and then roasted (220 degrees C for 10 min). To identify the irradiation treatment, physical detection methods like photostimulated luminescence (PSL), thermoluminescence (TL), and electron spin resonance (ESR) have been investigated before and after roasting. The photon counts of the irradiated samples (nonroasted and roasted) were higher than those of nonirradiated ones, making it possible to distinguish the two samples. The threshold values of nonroasted and roasted samples increased linearly with the irradiation dose, respectively. The TL for the nonirradiated nonroasted and roasted samples presented a lower peak at about 300 degrees C, but irradiated samples showed a higher peak at around 150 degrees C. The areas of TL glow curves were 15 times higher in nonroasted as compared with roasted samples. TL ratio [integrated area of TL 1 (the first glow)/TL 2 (the second glow)] obtained by the reirradiation step was 0 in nonirradiated samples and more than 0.15 in irradiated samples. The radiation-induced ESR signals originating from cellulose were determined in irradiated samples before and after roasting.

Detection of Free Radicals in Electron Beam-Irradiated Mucuna pruriens (L. DC.) Seeds by Electron Spin Resonance

Electron spin resonance (ESR) spectroscopy was employed to detect free radicals in raw Mucuna pruriens (velvet bean) seeds after electron beam irradiation (Microtron source: 0, 2.5, 5, 7.5, 10, 15 and 30 kGy) and conventional processing (roasting, powdering and cooking). The ESR signal of irradiated seeds (g=2.0055±0.0001) was more prominent in the seed coat than cotyledon. Seed coat of irradiated samples showed dose-dependent linear increase of this signal (g = 2.0055) accompanied by a weak triplet (satellite peak; aH = 3 mT) produced exclusively by radiolysis and could be used as an indication of successful irradiation. Irradiated cotyledon portion devoid of satellite peak (triplet) showed a linear increase in signal intensity up to 10 kGy with a sharp decline at higher doses (15 and 30kGy). Stability of radiation-induced ESR signals after 6 months of storage (25 ± 1°C) revealed the presence of a weak triplet with a substantial loss of signal intensity. Thermal effects such as roasting and powdering of seeds increased the signal intensity (g = 2.0055) similar to or in greater proportion than irradiation. Phenolics in seeds, which contribute significantly to detect free radicals in vegetative parts of a plant showed a waning trend in seed coat, while it was vice versa in cotyledon. Textural studies revealed significant loss in firmness after irradiation (p<0.05), which might favour in minimising the cooking time. Results of the present study might help to divulge the beneficial effects of application of electron beam irradiation technology as a better alternative to fumigants in seed preservation for safety and quarantine purposes.

Alanine-polystyrene dosimeters prepared by injection moulding

The alanine-polystyrene dosimeters analysed by electron spin resonance (ESR) spectrometry were manufactured for large-scale use as a routine dosimeter in industrial radiation processing facilities by using an injection moulding method. Injection moulding enables us to achieve mass production of uniform dosimeters at a reduced cost. Their primary characteristics for dosimetry were studied in terms of their gamma-ray dose-response at radiation processing dose levels, precision, and effect of temperature during irradiation at an absorbed dose of 1 kGy. The precision of dose-response in the range 0.1–100 kGy is within ± 2% at a 68% confidence level with and without correction for sample-to-sample mass scattering. The irradiation temperature coefficient for dosimeters irradiated to 1 kGy is estimated to be 0.25%/°C, by normalizing to those irradiated at 25°C in the temperature range from 5 to 45°C. The fading of the radiation-induced ESR signal at doses of 0.1–100 kGy at 25°C and r.h. 40% is <1% for at least 2 months after irradiation.

The effect of processing treatments on the radiation-induced ESR signal in the cuticle of irradiated Norwat lobster ( Nephrops norvegicus).

Cooked, frozen or chilled whole tails of Norway lobster were either not irradiated or given doses of 1, 2, 3, 4 or 5 kGy using a cobalt 60 source. The cuticle was removed, freeze-dried and ground before determination of the free radical concentration using electron spin resonance (ESR) spectroscopy. The ESR signal strength increased linearly with increasing irradiation dose. In comparison to the chilled samples, cooking before irradiation significantly increased (69%) signal intensity whereas cooking after irradiation decreased (27%) signal strength. Irradiating the samples in the frozen state did not significantly alter the free radical concentration in the cuticle.