Jiunn-Guang Lo

Radiochemical separation by magnesium oxide adsorption and applications

The radioactive tracer technique was used to investigate the adsorption behaviour of 47 ions onto hydrous magnesium oxide. Detailed studies on Co(II), Zn(II), La(III) and Ce(III) reveal that the adsorption isotherms of these ions obey Langmuirs law. Radiochemical separation using hydrous magnesium oxide was applied to the RNAA of NBS standard reference materials, and satisfactory results were obtained. Hydrous magnesium oxide was also used to adsorb various ions from aqueous solution for the purpose of preconcentration which was followed by NAA or ICP-AES analysis. Satisfactory results have been observed in both methods.

Chemical characterization of complexation behavior of pertechnetate with cysteine

The labeling behavior of cysteine with99TcO4− ion and/or99mTcO4− ion at different cysteine concentrations reductant and pH values has been studied by chromatography, and the labeling yield was calculated. Three major Tc-complexes, yellow, reddish brown and green can be separated by gel filtration chromatography (GFC). Thin layer chromatography (TLC), high performance liquid chromatography (HPLC) and ion-exchange chromatography (IC) were used to separate the complexes collected from GFC. The TLC, HPLC data show the pertechnetate accompanied with a yellow complex; the green and purple complex contain more than two complexes. Electrophoresis and IC data show that the complexes carry a negative charge. The conductivity, UV-VIS, flow beta-detector with HPLC and autoradiography are also applied to analyze complex formation.

Evaluation on chemical neutron activation analysis for trace metals in seawater using magnesium oxide as the preconcentration agent

Attempts have been made to employ magnesium oxide as the preconcentration agent for determination of trace metal sin seawater by neutron activation analysis. Hydrous magnesium oxide can efficienthy adsorb most cationic transition metals and rare earths in a simple water system. The adsorption behavior is believed to depend mainly from the association of the cationic species of the metals with MgO22− adsorbent. In seawater matrix some of the metal ions such as Hg2+, Ni2+, etc. may become inefficiently adsorbed owing to the formation of highly stable metal-chloro complexes with chloride ion. Usually the adsorption efficiencies of the metals can be recovered to be as high as the case in the simple water system if an acidified seawater (to pH≤1) is subjected to the adsorption experiment. In practice, a large volume of seawater (5 1) is stirred with a small amount of hydrous MgO (1 g). Thereafter, the trace metals adsorbed MgO is separated and taken to be neutron activated. The abundant sodium ion and ubiquitous bromide ion can be obviated by the adsorption process, thereby beneficial to the γ-spectrometry of the metals enriched on MgO.

Recoil chlorine reactions with ethylene

The reactions of recoil38Cl atoms produced through the37Cl(n,γ)38Cl process in the CF3Cl−C2H4 gas phase are described in this work. The CF3Cl is a chlorine source as well as moderator. Scavengers, such as O2 and H2S, were added to the system to discriminate the reactions induced by energetic and/or thermal chlorine atoms. The radioactive38Cl-labeled products were separated using gas-chromatogarphic technique followed by an external proportional counter for quantitative determination of the product yeids. The mechanisms of the chemical reactions are predicted to account for the formation of these organic compounds.

Determination of extraction constants for metal pyrrolidinedithiocarbamates and chloride-mixed metal pyrrolidinedithiocarbamates by substoichiometric extraction

Substoichiometric extraction in conjunction with a double tracer technique is employed to simultaneous determination of extraction constants of simple metal pyrrolidinedithiocarbamates and chloride-mixed metal pyrrolidinedithiocarbamates. The metals involved include Hg(II), Bi(III), In(III), As(III), Cd(II) and Fe(II). The extraction constants for Bi(III) and Cd(II) obtained are compared with the values available in the literature. The extraction constants for all the other metals are reported for the first time.

Determination of small quantities of51Cr(III) in the presence of large quantities of51Cr(VI) by coprecipitation with zinc hydroxide

A procedure is described for the determination of51Cr(III) in51Cr(VI) samples having a51Cr(VI) to51Cr(III) ratio of 105, by means of a single zinc hydroxide coprecipitation at apH of ca. 13. Acceptable precision (standard deviation of 10–15%) is possible with solid51Cr(VI) samples containing 10 ppm of51Cr as51Cr(III).

On-line method for measurement of the dispersion coefficient of radionuclide migration using a column method

An on-line method to obtain breakthrough curves from a conservative tracer generated in crushed rock columns has been introduced. The breakthrough curve can be used to evaluate some important hydrologic parameters for studying radionuclide migration in groundwater system. These parameters include the dispersion coefficient, average flow yelocity, effective porosity, and retardation factor of the columns tested. A conservative radiotracer,131I, was used to generate the breakthrough curves, and linear regression analysis was applied to obtain the optimum value of dispersion coefficient. The effects of the injected volume of radioactive tracer, average flow velocity, and effective diameter of packed material on the dispersion coefficient as well as the stability of the packed material, and their in-situ application are discussed.

Reaction of recoil tritium atoms with ethyl alcohol in the gas phase

Reaction of recoil tritium atoms with ethyl alcohol in the gas phase has been studied in the presence of moderator and scavenger. The total amount of tritium produced from3He (n, p) T reaction under given irradiation conditions is determined by adding methane as a monitor for each set of sample. The HT, CH3T, C2H5T and C2H4TOH yields were due to the decrease of hot reaction with increasing moderator pressure. On the other hand, the C2H3T yield, due to the unimolecular reaction of excited CH4TOH* or C2H5T* moleculas, decreased with increasing pressure. All tritiated compounds were analyzed by radio gas chromatography.

An alternative intraarterial therapeutic agent for hepatic tumors:131I lipiodol/histoacryl mixture

Lipiodol has excellent retainable ability in hepatoma cells. This agent can be labeled with radioisotope (131I) and mixed with tissue adhesive (Histoacryl), and then alttached on the lesion of liver by intrahepatic arterial administration. In this study, we attempt to obtain the optimal ratio of Lipiodol to Histoacryl and evaluate the consolidation of blood in vitro and toxicity and biodistribution in vivo. The ratio of131I Lipiodol/Histoacryl mixture (L/H), concentration of heparin and flow rate of blood are varied by simulating the installation of bloodstream to test the time of consolidation. In addition, the optimal ratios of the L/H mixtures are assessed in vitro in heparinized human blood. According to those results, Lipiodol and Histoacryl mixed with 1∶1 or 2∶1 ratio have an ideal time of 13 to 15 seconds in vitro; in addition, 1.2∶1 ratio is an optimal ratio in the biodistribution study. Interestingly, heparin and acetic acid does not alter the consolidation time, in addition, no variation occurs when varying the flow rate of blood. The consolidation of L/H mixture with blood is incubated in the 37°C, normal saline bath for 24 hours. No dissociation of free131I is found. The optimal mixture is also injected into the hepatic artery of the Sprague-Dawley rats carrying for 24 hours. No dissociation of free131I is found. The optimal mixture is also injected into the hepatic artery of the Sprague-Dawley rats carrying hepatocellular carcinoma (NIS1 cell line). Radioactive consolidate is well confined in the tumor without evidence of leakage of the mixture to the lung or distribution of free131I in the thyroid. In conclusion, this mixture has the merits of both irradiation and embolization of the tumor. The131I Lipiodol/Histoacryl mixture (1.2∶1) is a promising alternative for intrahepatic arterial administration to treat hepatic tumors. Histoacryl can confine the131I and, also, embolize the tumor vessels.

Instant capture of recoil51Cr(III) from neutron activated K2CrO4

We have recently developed a new method of measuring the initial51Cr(III) produced from nuclear recoil of K2CrO4. In our method, K2CrO4 was mixed with MgO in the presence of a small amount of water, and the mixture was irradiated in a nuclear reactor. After irradiation, the mixture was dissolved in water, and MgO precipitate was separated from the solution. The yield of recoil51Cr(III) could be calculated from the51Cr activity in the precipitate measured. On the other hand, the yield of retention of51Cr as chromate could be calcualted from the activity found in the supernatant. The51Cr(III) yield thus obtained is almost a factor of 2 higher than observed in pure K2CrO4 without mixing with MgO, irradiated under the same condition. Another important observation is that the51Cr(III) yield is independent of irradiation time in the presence of MgO. Without MgO, the observed51Cr(III) yield decreases with increasing irradiation time, suggesting possible oxidation of Cr(III) to chromate during irradiation. This variation is not observed in the system of K2CrO4 containing MgO, indicating that the initial Cr(III) is adsorbed immediately after nuclear recoil by MgO and is protected from oxidation by gamma radiation.