Abstract
Neutron activation analysis have been applied to elucidate the distribution of several trace elements in rice plant. The seed, stem, leaf, chaff and grain samples (1g each) were irradiated for 5 or 30 min with the Tsing Hua University Reactor or the Kyoto University Reactor (swimming-pool type, 1 MW, 2-4×1012 thermal neutrons/cm2/sec) through the pneumatic tube systems. After the irradiation, manganese, sodium, and potassium could determine non-destructively without any chemical treatment. Chlorine, bromine, copper, and zinc were determined after some radiochemical separation treatments. The induced radioactivities in the non-separated and the separated specimens were measured by the gamma-ray spectrometries, using a TMC 100-channel analyzer with a 2 in.×2 in. NaI scintillator or a RCL 512-channel analyzer with a 3 in.×3 in. NaI scintillator. The outline of the analysis is shown in Table 1. In the potassium determination, a spectrum-stripping method to eliminate the sodium interference was applied. In the destructive method, the irradiated samples were decomposed with mixtures of conc. H2SO4 and conc. HNO3. Chlorine and bromine were determined in the acidic distillates through the silver salt precipitations, and copper and zinc in the residual solutions through the chloride anion exchange and the oxine salt precipitations. All the chemical yields were more than 95%. The typical gemma-ray spectra are shown in Fig. 1-7 and the analytical results in Table 2. The experimental errors were 3-5% in the manganese, 5-10% in the sodium, the potassium, the chlorine, the bromine and the copper, and 10-20% in the zinc analyses. From the experimental results shown in Table 2, it was clarified that chlorine tends to be concentrated in seed, manganese, sodium, and bromine in leaf, potassium in stem. These distribution effects may reflect the metabolic specificity in organ of rice plant.
