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壳聚糖的光度测定新方法 总被引:3,自引:0,他引:3
研究了以刚果红分光光度法测定壳聚糖,探讨了最佳实验条件及干扰因素的影响。在pH9.7时,刚果红和壳聚糖形成有色物质,检测波长为543.5nm,线性方程为:A=0.0200ρ+0.0156,R^2=0.9978。在0~20.00μg/mL范围内呈现良好的线性关系,平均回收率为99.20%。采用该方法测定了两种复方样品中的壳聚糖,方法的选择性和灵敏度良好。该方法可用于检测复方样品中少量的壳聚糖。 相似文献
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壳聚糖富集火焰原子吸收法测定水中痕量铜 总被引:8,自引:2,他引:8
采用壳聚糖修饰钨丝基质螺旋卷,直接浸入含有痕量铜的pH5.0的Brltton-Robinson缓冲溶液中,经电磁搅拌富集一定时间后,将其转移至空气/乙炔火焰燃烧器上,利用火焰原子吸收光谱法简便快速测定水中痕量铜。方法的线性范围为2—75μg/L;检出限为0.98μg/L。同一支钨丝螺旋卷重复涂敷壳聚糖富集Cu,RSD(n=6)为2.7%。 相似文献
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在固定床积分反应器中,对Fe-Mn催化剂上F-T合成反应的初期反应性能进行了一系列条件实验,考察了在不同温度、压力、原料气H2/CO比和空速下催化剂的催化性能.结果表明,该催化剂运行200h后,仍显示出较高的催化活性和稳定性,对低碳烯烃和C5+烃具有较高的选择性,且C5+烃的时空收率较高.在n(H2)/n(CO)=1,GHSV=6000h-1,p=2.02MPa和θ=300℃的条件下,CO转化率可达74.1%,总有效烃(C=2~4+C5+)的选择性可达88.6%,甲烷选择性为6.7%,C5+烃的时空收率为0.54g/(ml·h). 相似文献
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磷酸钛—磷钨酸铵的合成及性能研究 总被引:1,自引:0,他引:1
本文研究了磷酸-磷钨酸铵的合成,离子交换性能及化学结构等方面的性质。实验结果表明,该交换剂对Cs^2+具有很高的选择性和交换容量,在0.1mol/L HNO3介质中,该交换剂对Cs^=的交换容量可达0.95mmol/g,在1AW模拟废液中,对CS^+离子仍保持较高的变换容量。 相似文献
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本文研究了以一系列离子液体作为介质时,萃取剂二环己基18冠6(DCH18C6)对水相中Sr^2+的萃取行为.研究结果表明,DCH18C6/离子液体体系对Sr^2+的萃取性能优于相应的DCH18C6/JE辛醇萃取体系,一定条件下其萃取Sr^2+的分配比可达10^3量级.同时,体系对Sr^2+的萃取性能随着离子液体的结构不同而有所差别.在离子液体萃取体系中,随着水相初始硝酸浓度的增加,对Sr^2+的萃取性能下降.水相中Na^+、K^+等离子的存在也会对体系萃取Sr^2+产生直接影响.本文还验证了离子液体体系萃取Sr^2+的机理,即以阳离子交换机理为主实现对Sr^2+的萃取. 相似文献
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流动注射碳硅凝胶微柱预富集ICP—AFS法测定高纯氧化铕中的非… 总被引:2,自引:0,他引:2
利用自合成的碳硅凝胶为吸附材料,以铜试〔二乙基二硫代氨基甲酸钠(NaDDTC)〕为衍生化试剂。柱前衍生的方法,在优化的实验条件下,于pH4.6的缓冲介质中在线预富集Al^12+、Cr^5+、Cu^2+、Fe^3+、Pb^2+、V^5+、Zn^2+。采用停流技术洗脱,富集倍数可达8.1 ̄12.6倍,检出限为ng/ml级。对高纯氧化铕(Eu2O3)中的非稀土杂质进行测定,可避免大量稀土基体对测定的干扰 相似文献
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分光光度法测定豆类中铝含量 总被引:6,自引:1,他引:6
用分光光度法测定了豆类中的铝含量。利用Al^3+在乙酸-乙酸钠缓冲介质中,与铬天青S(CAS)及十六烷基三甲基溴化铵(CTMAB)反应形成蓝色三元络合物,在610nm处测定其吸光度,并对CTMAB质量浓度进行了最佳选择。结果表明,该法提高了测定灵敏度。10种豆类中的铝含量中绿豆的铝含量最高,29.49μg/g;菜豆的铝含量最少,8.24μg/g;10种豆类的平均铝含量为15.33μg/g。可见豆类中的铝含量很低,建议放心多食豆类食品。 相似文献
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用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%. 相似文献
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The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula. 相似文献
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Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction
Laurent Gavara Thomas Boisse Jean-Pierre Hénichart Adam Daïch Philippe Gautret 《Tetrahedron》2010,66(38):7544-5571
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments. 相似文献
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Rebecca J. Burton Mandy L. CrowtherNeal J. Fazakerley Shaun M. FilleryBarry M. Hayter Jason G. KettleCaroline A. McMillan Paula PerkinsPeter Robins Peter M. SmithEmma J. Williams Gail L. Wrigley 《Tetrahedron letters》2013
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines. 相似文献
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KMnO4-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields. 相似文献
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N. A. Nedolya 《Chemistry of Heterocyclic Compounds》2008,44(10):1165-1219
The review contains a concise historical account and information on the most significant researches undertaken by the staff
at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry
of Heterocyclic Compounds.
Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008. 相似文献
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Regiospecific and direct imidation of the methyl C(sp3)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products. 相似文献
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《Tetrahedron》2014,70(21):3377-3384
The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative. 相似文献
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Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner. 相似文献