A radiochemical separation procedure has been set up to determine Ir of 10–12 g/g level and other noble metals in geological samples by using a long chain s-alkyl primary amine, N-1923, as an extractant. A series of factors affecting the chemical recovery of Ir were considered, including extractant, diluent, oxidant, oxidation temperature an time, extraction acidity, reflux acidity and time, etc. Some improvements in the procedure for geological samples were made, i.e. eliminating interference from chromium and raising recoveries of noble metals in geological samples. The extraction percentages of noble metals are more than 95% in one step of extraction and of base metals are generally less than 0.5%.
Authors:Xiaolin Hou, Xiaojun Yan, and Chifang Chai
The distribution of iodine in various biological macromolecules in Sargassum kjellmanianum was studied using neutron activation analysis combined with chemical and biochemical separation techniques. The results indicate that iodine is mainly bound with protein, part of iodine with pigment and polyphenol, and little with polysaccharides, such as algin, fucoidan and cellulose. This result is significant for the mechanism of enriching iodine of algae and utilization of alga iodine.
The cadmium and boron ratios from 44 elements, totally 66 nuclides, were determined in the inner and outer irradiation sites of the Miniature Neutron Source Reactor (MNSR). China Institute of Atomic Energy. A permanent Cd-shielded epithermal neutron irradiation site has been designed and installed in the outer of the beryllium reflector of this reactor. Elements e.g., I, Br, Sr, Si, Th and U in biological samples, such as foodstuff, water and blood, geological and environmental samples, such as soil, rock, sediment and vegetable leaves were analyzed by BN-shielded epithermal neutron activation analysis (ENAA), and Au, As, Sb, Th and U by Cd-shielded ENAA. The results show that the detection limits of these elements by ENAA are better by a factor of 1.5–7 than those with conventional NAA.
Authors:Chifang Chai, Yongzhong Liu, and Xueying Mao
The isotopic abundance ratios of190Os/184Os and96Ru/102Ru for the metal phases of the Jilin and Taonan stone meteorites were determined by pretreatment and radiochemical neutron activation analysis. All experimental factors affecting Os and Ru isotopic ratios were discussed, including sampling, standard, irradiation, separation and counting. The statistical errors of measurement for the199Os/184Os ratio can be controlled within 1%. The experimental results indicate that the statistically significant anomalies of the190Os/184Os and96Ru/102Ru ratios have not been found relative to the terrestrial Os and Ru standards.
Authors:Kong Ping, Chai Chifang, Mao Xueying, and Ma Shulan
The geological samples: Cretaceous-Tertiary (K-T) boundary clays, meteorites, volcanic lava, and ultrabasic rock were separated into carbonate, metal, sulfide, oxide, silicate and acid-resistant residue by a selective chemical dissolution procedure developed in our laboratory. Some conclusions were drawn by analyzing the chemical speciation of anomalous iridum in the above samples and especially by studying the characteristics of mineral components in those residue phases. (1) It is impossible that the anomalous Ir was caused by geochemical enrichment; (2) The iridium enrichment in the K-T boundaries did not necessarily associate with kerogen; (3) The volcanic activity has participated in the extinction event at the end of Cretaceous; (4) Extraterrestrial impact was the trigger of K-T event. Then, we proposed a mixed model by which the extant anomalous Ir in K-T boundary clays was interpreted as a combined effect of extraterrestrial impact, volcano eruption and post-depositional redistribution.
Authors:Chai Chifang, Ding Zhuguo, Fu Jiamo, and Sheng Guoying
A combination of Soxhlet extraction, column chromatography and INAA with GC and GC-MS was used in this work for the study of the abundance patterns of 36 trace elements and their correlation in nearly 100 samples of crude oil and organic materials extracted from oil-forming source rocks from 10 main Chinese oilfields. The low V/Ni ratios of 0.01 to 0.3 state the oil-forming continent environment. The geochemical significance hinted from other trace element abundances is also briefly discussed.
Authors:Tian Jibing, Qian Qingfang, Chai Chifang, Wang Ke, and Ou Tong
A biochemical technique was used to separate three kinds of proteins (albumin, globulin and gliadin) in corn samples from high selenium areas and normal areas in Erxi autonomous region of Hubei Province, China. The contents of Se and other elements in these proteins were determined by neutron activation analysis (NAA). The results show that Se is enriched in corn proteins at high selenium area, while Cu, Al, Mn, V and Cl are also enriched in varying degrees.
Authors:Xiaolin Hou, Yongbao Zhang, Chifang Chai, Guodong Liu, Ke Wang, and Qinfang Qian
Neutron activation analysis (NAA) was used to determine the concentrations of 6 elements Cr, Co, Rb, Cl, Br and I in 12 kinds of Chinese diets. The daily dietary intakes of these elements in 4 areas groups of China were investigated and the analytical results were compared with other countries and WHO recommended dietary intakes.