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51.
Weike Zhong Diandou Xu Zhifang Chai Xueying Mao 《Journal of Radioanalytical and Nuclear Chemistry》2004,259(3):485-488
Instrumental neutron activation analysis (INAA) has been used for the determination of extractable organohalogens (EOX) in
milk. The detection limits are 50 ng, 8 ng and 3.5 ng for Cl, Br and I, respectively. The EOX concentrations in milk samples
from various regions of China were determined. Meanwhile, organochlorine pesticides residues were detected by gas chromatography.
The concentrations of the EOX in the milk samples are decreasing in the order of EOCl >> EOBr > EOI, and EOCl accounts for
95% of the total EOX. The average concentration of EOCl in milk is 4.44 ·g/g expressed as fat weight basis, with the highest
value of 17.6 ·g/g from South China. The mean concentrations of total HCH and DDT are 0.038 ·g/g and 0.046 ·g/g, respectively.
Organochlorine pesticides account only for 1.6% of the EOCl, indicating the very high proportion of the unknown EOCl in the
milk sample.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
52.
稀土萃取分离过程自动控制研究现状及发展趋势 总被引:9,自引:2,他引:9
在简要描述稀土萃取分离生产过程的基础上,综述了目前国内外稀土萃取分离过程中稀土元素成分在线检测的方法、装置及其应用现状;稀土串级萃取分离生产过程的计算机流程模拟以及稀土萃取生产过程的自动控制方法、技术及其应用现状.指出了稀土元素组分含量的软测量方法,以综合生产指标为目标的稀土萃取分离生产过程优化控制方法以及由生产过程管理系统和过程控制系统两层结构组成的稀土萃取分离生产过程综合自动化系统已成为稀土萃取分离生产过程自动化未来发展的方向. 相似文献
53.
通过三碘化锑和三碘化铋与硫脲间的室温固固反应合成了三碘化锑、三碘化铋的硫脲配合物 ,其组成为 :M[CS( NH2 ) 2 ]3 I3 ( M=Sb,Bi)。两种配合物的晶体结构均属于单斜晶系 ,锑配合物 Sb[CS( NH2 ) 2 ]3 I3 的晶胞参数为 :a=1 .4 772 nm,b=1 .6 5 82 nm,c=2 .0 6 74 nm,β=90 .81°,铋配合物 Bi[CS( NH2 ) 2 ]3 I3 的晶胞参数为 :a=1 .4 0 1 0 nm,b=2 .0 1 6 8nm,c=2 .0 397nm,β=90 .84°。远红外光谱表明硫脲中的 N原子而非硫原子参与了配位 相似文献
54.
55.
This study developed a phase reaction conversion (PRC) headspace gas chromatographic (HS-GC) technique for the measurements of nonvolatile species in liquid or solid samples. The technique is demonstrated by the measurements of carbonate in aqueous carbonate solutions and in kraft pulp mill liquor samples. A very small amount of sulfuric acid (volume of 0.5 ml, concentration of 2 mol/l) is used to acidify a sample of less than 300 microl in volume and convert the dissolved carbonate into carbon dioxide (gas) in a sample vial (reactor) that is analyzed by thermal conductivity detection through a headspace sampler. The carbonate concentrations measured by PRC-HS-GC in seven kraft liquor samples agree very well with those measured using a coulometric and a titrametric method. Simultaneous analysis of multiple species was also conducted to demonstrate the versatility of the method. The present method is very simple, rapid, reliable, accurate, and fully automated. It can be applied to analyze other nonvolatile species in various industrial and environmental samples. 相似文献
56.
本文采用以ASED-MO(含原子对排斥的EHMO法)为基础的结构自动优化的EHTOPT法及Monte-Carlo法, 对甲醇羰基化制乙酸催化剂的共聚物配体交替结构进行了理论研究。计算了AA, AB, BB, BA二聚反应的反应途径, 找出了过渡态, 并确定了反应活化势垒。在假设两反应频率因子相同的前提下, 求出竞聚率, 采用Monte-Carlo法模拟共聚物结构, 计算出共聚物配体中起催化活性的AB交替结构所占比率。比较不同共聚物配体的活性, 并研究了温度及单体配比对共聚物配体交替结构的影响。 相似文献
57.
A chemically modified platinum electrode with coated poly[tetra(4-aminophenyl)porphyrin] has been used as a potentiometric pH sensor. It gives a linear response over the pH range 1.5-13.7 with a slope of 55 mV/pH (at 20 degrees ). The sensor has fair resistance to erosion of hydrofluoric acid and to interference of a coexisting redox couple. The sensor can be used for pH determination and end-point indication for potentiometric titration of hydrofluoric acid with sodium hydroxide. The a.c. impedance of the polymer membrane has also been studied. 相似文献
58.
H. Zhang Z. F. Chai H. B. Sun J. L. Zhang H. Ouyang L. Xin Y. D. Chuai 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(1):31-35
The concentrations and distributions of total halogen (TX), extractable organohalogen (EOX) and extractable persistent organohalogen
(EPOX) were determined in 20 kinds of yogurt specimens collected from Chinese supermarkets using neutron activation analysis
(NAA) and gas chromatography equipped with a 63Ni electron capture detector (GC-ECD). The results indicated that the halogens in yogurt mainly existed as non-extractable
organohalogen compounds. About 25–30% of EOX was EPOX. EOCl and EPOCl were the main organohalogen species in yogurt. The average
concentration of the identified organochlorine, such as organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs),
was below 4% of EPOCl. 相似文献
59.
C.Akira Horiuchi Akinori Takeda Wen Chai Kishoh Ohwada Shun-Jun Ji T.Tomoyoshi Takahashi 《Tetrahedron letters》2003,44(52):9307-9311
A novel reaction of α-iodo ketone (α-iodocycloalkanone, α-iodo-β-alkoxy ester, and α-iodoacyclicketone) with irradiation under a high-pressure mercury lamp gave the corresponding α-hydroxyketone in good yields. In the case of α,α′-diiodo ketone, α,α′-dihydroxyketone which little has been reported until now was obtained. This reaction affords a new, clean and convenient synthetic method for α-hydroxy- and α,α′-dihydroxyketone. 相似文献
60.