S. J. Yeh

Neutron activation analysis for trace elements in unpolished rice

Abstract Twenty-two elements in 19 unpolished rice samples harvested in Taiwan during 1973 have been determined by a neutron activation analysis technique, consisting of both non-destructive and destructive methods. After the removal of 24 Na and 32 P, chemical separation into three groups is achieved by anion exchange and distillation. The concentrations of heavy metals in different rice samples vary widely.

Determination of mercury in human urine by neutron activation analysis, with lead diethyldithiocarbamate as a preconcentration agent

Abstract Lead diethyldithiocarbamate is an effective reagent for preconcentration of mercury in urine for neutron activation analysis. Sodium and bromine are removed from the sample by this procedure. As lead diethyldithiocarbamate is insensitive to neutron activation, radiochemical separation is not needed after neutron irradiation. Results from the analysis of urine collected from workers in caustic soda manufacturing plants are discussed.

Determination of trace amounts of rare earth elements by neutron activation analysis after preconcentration using hydrated magnesium oxide

A preconcentration method of 13 rare earth elements (REES) was studied for neutron activation ananlysis (NAA). Hydrated magnesium oxide was used as the preconcentration agent to absorb the REES ions from aqueous solution onto the solid magnesium oxide, which was separated and analyzed. It was observed that the Langmuir equation for isothermal adsorption was well obeyed by the REES under the condition studied. The efficiency of the preconcentration process using hydrated magnesium oxide was critically examined for each of REE and for mixture of REES by preparing a known volume of solution containing known amount of trace REES. NAA was used to analyze REES recovered by the preconcentration process. It was found that the REES recoveries were satisfactory and the preconcentration process is reliable. There are several resort resort areas in Taiwan where local people are enjoying its hot spring water. It is generally believed that the hot spring water spa would bring about some sorts of therapeutic functions. The preconcentration method developed above, was applied to analyze the trace amounts of REES in hot spring wate in Taiwan.

Determination of the extraction constant of gold diethyldithiocarbamate dichloride by substoichiometric extraction

Abstract Radioactive gold(III) with radioactive palladium(II) as reference ion in a chloride medium was substoichiometrically extracted with zinc diethyldithiocarbamate in chloroform. A formula for calculation of the extraction constant of the gold(III) complex was derived, for which only the values of distribution ratios of gold and palladium between the two phases had to be measured experimentally. The extraction constant was found to be log K = 68.9 ± 0.4.

Determination of impurities in the eluate of rhenium generator using hydrated magnesium oxide as the preconcentration agent

In recent years chances of using rhenium-186 and rhenium-188 as radioactive isotopes in diagnostic and therapeutic applications are increased very much due to the characteristic radiochemical and chemical properties of these two radioisotopes. In particular, chemical similarities between99Tc and99mTc pair and186Re and188Re pair make it easier to correlate the two groups of compounds. Rhenium-188 is generated from the beta-decay of tungsten-188 which was produced by double neutron capture on enriched tungsten-186 oxide. It is of great interest to examine the impurities in the eluate by radiochemical neutron activation. For this purpose, the preconcentration of the impurities in samples were necessary, and it was achieved by adsorption on hydrated magnesium oxide.

Determination of rare earth elements in Taiwan monazite by chemical neutron activation analysis

Taiwan monazite is a unique mineral obtained from the heavy sand found in the river floor of Tzuo-suei river and En-suei river. Both rivers are flowing parallel with separated narrow area into the sea at southwestern coast of Taiwan. The characteristic of monazite is that it contains considerable rare earth elements (REEs). REEs are considered very useful elements in the local industries and scientific researches such as ceramic, semiconductors, and glass optics. In this study, chemical neutron activation analysis (CNAA) was used to determine the contents of REEs in Taiwan monazite. A few milligram of monazite was digested in the microwave oven for 25 minutes with mixed acid (conc. HNO3 and HClO4). REEs were preconcentrated by hydrated magnesium oxide and CNAA was performed.

Determination of trace elements in surface water by neutron activation analysis

In order to assure the public health, simple and relibable analytical methods must be established for effective surveillance of polluted surface water. Since the pollutants in surface water are usually found at ultratrace levels, preconcentration is generally required to ensure the quality of the analytical results. An analytical procedure consisting of preconcentration using hydrous magnesium oxide followed by neutron activation analysis has been proposed and applied to the determinations of trace elements in surface water.

Determination of trace elements by neutron activation analysis using dinonylnaphthalene sulfonic acid as a preconcentrating agent

Dinonylnaphthalene sulfonic acid (HD) has been used as a preconcentrating agent to enrich trace metal ions and to separate the interfering elements such as Na, K, Cl and Br which normally exist in the natural aqueous systems. Experiments were performed by extracting the ions in the aqueous medium with HD in n-hexane and subsequently back-extracted into a minimal volume of acid solution. Factors influencing the extraction efficiency of the ions of interest were investigated. The preconcentration technique developed in this study was applied to the determination of trace elements in biological and natural water samples by neutron activation analysis.

Determination of trace amounts of rare earth and representative elements in waste water samples by chemical neutron activation analysis

An attempt was made to establish a reliable method using chemical neutron activation analysis for surveillance of pollutants in waste waters released by plants manufacturing various kinds of products. Since preconcentration process played important role in the entire course of the analysis work, special precaution was taken to re-confirm that the recovery efficiencies for pollutant ions were satisfactory during the preconcentration. It was also re-examined that the Langmuirs adsorption isotherm pattern well obeyed by all ions under investigation. In recent years, significant amounts of rare earth compounds and other raw materials containing representative elements have been imported and consumed to meet the demand due to the rapid progress in new manufacturing technology. Samples were collected from ten various production lines in plants and potential pollutants were determined using the Tsing Hua Open-pool Reactor. It would be noteworthy that the specimens obtained by this preconcentration process also would be usable for Induced Coupled Plasma-Mass Spectrometry analysis for supplementary and/or comparison purposes.

Preconcentration on hydrous magnesium oxide for neutron activation analysis

It was found that trace amount of various ions could be effectively adsorbed onto hydrous magnesium oxide from aqueous solution. Attempts were made to investigate the feasibility of using hydrous magnesium oxide as preconcentration agent for neutron activation analysis (NAA). The procedure was successfully applied for the measurements of trace amounts of elements in the surface water of a number of large rivers which play very important roles in the lives of local people. Some of them are polluted rather badly. In order to improve the living standards it is rather important to establish reliable analytical methods so that more effective surveillance may be enforced on pollution control problems. NAA is generally accepted as one of the most suitable methods for simultaneous and multielemental determination of trace amounts of elements. In this work polluted surface waters were investigated by NAA using Tsing Hua Open-pool Reactor (THOR).