| This research established a novel method for irradiation dose determination byusing ascorbic acid (AA), thiamine hydrochloride (TH) and riboflavin (RF) asradiation materials. Mechanism of irradiation effect on these material was studied bychemical method, mass spectrometry (MS) and nuclear magnetic resonance (NMR).The experimental conditions were optimized, and the influencing factors, as well asthe suitable ranges of application were systematically studied. Accumulationirradiation dose could be determined by high performance liquid chromatography(HPLC) as a new technique due to the irradiation characteristics of vitamins.Compared with other chemometric resolution method, the chromatographicmeasurement method is much simple in its operation, and easy to popularize, whichreflects the characteristics of high performance liquid chromatography (HPLC).Substances could be separated by chromatographic column automatically and resultswith high accuracy could be ensured. The materials (vitamins) are easily available,non-radioactive and no special treatment is needed. This method could be used inradiation field, and, it also provide a new way to be applied in "radiation and botany"and "radiation preservation and nutrition of vegetables" research as it provides thefoundation method.Chapter2: Based on the degradation effect of ascorbic acid (AA) caused by highenergy which given off by60Co irradiation, a new method for determining γ rayradiation dose was observed. Samples of ascorbic acid that had accepted radiationwere separated and tested by HPLC method. Tests showed that between the twoconcentrations of0.5mg/ml and1.0mg/ml, peak area of AA forms good linearitywith irradiation dose. AA of0.5mg/ml was suitable for ranges of10kGydetermination and1.0mg/ml could be applied within14kGy measurement with thecorrelation reached0.996. Sensitivity and accuracy could be ensured by HPLC method as AA and the degradation could be separated for detection. Degradationmechanism were studied by chemical pathway, MS and NMR, which showed that thedegradation is an oxidation process caused by irradiation, and, the same radiovariations of AA could be simulated by hydrogen peroxide.In the chapter3, a novel method of using thiamine hydrochloride (TH) asradiation dosimeter was reported. As TH is easily soluble in water, two concentrationsof0.3mg/ml and0.2mg/ml were selected. Solutions of TH after radiation treatmentwere tested by HPLC and the results showed that there was good linearity betweenthe residue of TH content and irradiation dose. Chemical method, MS and NMR wereused to analyze the irradiation mechanism, which testified that the molecular of THcould be decomposed by γ ray into thiazole and pyridine fragments. With externalstandard method to determine the content, linearity between dose(D) and peak area(A)were established. Concentration of0.3mg/ml TH which could be applied whithin10kGy and2.0mg/ml was suitable for0.1~20kGy dose measurement with thecorrelation reaches0.995. The results showed that TH solution was stable toward hightemperature and visible light, which make it convenient for storage. In order tooptimize the experimental conditions, different influencing factors such asconcentration, oxygen, different temperatures and acid effect were discussed. Thismethod is simple, cost-effective and satisfactory results could be obtained.Chapter4: Based on preliminary tests of the relationship between radiation andvitamins, different concentrations of some water soluble vitamins in B family wereselected for radiation research. The radiation characteristics of thiamin hydrochloride(TH), nicotinic acid (NA) and riboflavin (RF) in relative lower radiation intensity(under2000Gy) and feasibility to be used as dosimeter were studied. By contrast, RFis more sensitive toward γ ray, and, the changes of UV spectra were accord with thatof the fluorescence spectra which both showed that the content of RF would beslowly diminished by the increasing radiation intensity. The content (A) has goodlinearity with irradiation dose (D) and suitable for measuring dose ranges. Theselection of suitable concentrations of RF solutions, ranges for measurement, influencing factors as well as radioactive mechanism were studied. This method issensitive with lower radiation and thus suitable to be used as food radiation dosimeter.In addition, the method has high operability and good repeatability. |
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