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《理化检验(化学分册)》2010,(12)
采用静态法研究了HD-8阳离子交换树脂对铜的吸附速率、吸附温度和吸附量等性能。试验结果表明:在0.1~0.5mol·L~(-1)盐酸溶液介质中铜的吸附率在95%以上,用3mol·L~(-1)盐酸溶液3mL可将吸附于柱上的铜(Ⅱ)完全洗脱下来。在优化的试验条件下,该HD-8阳离子交换树脂微柱对铜的富集限为2μg/200mL,富集倍数为67倍。在此基础上提出了一种阳离子交换树脂分离分光光度法测定水样中痕量铜的方法。该方法用于测定鄱阳湖水中痕量铜,测得平均回收率为101.5%之间,相对标准偏差(n=5)为1.82%。 相似文献
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研究了电感偶合等离子体发射光谱法测定二氧化铀(UO2)中痕量磷和硅元素含量的方法。经过对HNO3,H2O等试剂的多级纯化,获得超低空白的高纯试剂。对样品溶解、待测杂质元素与铀基体分离等过程从机理方面进行了研究。在分离铀基体与硅元素时用磷酸三丁酯(TBP)作萃取剂,二甲苯作为稀释剂;在分离铀基体与磷元素时用三辛胺(TOA)作萃取剂,二甲苯作稀释剂。二氧化铀中磷、硅元素检出限分别为0.012,0.078μg/g,加标回收率分别为98%,96%,相对标准偏差小于4%(n=6)。该方法重现性好、检出限低,满足生产和科研检测要求。 相似文献
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在分析化学定性分析教学中,按硫化氢系统分组法将阳离子分为V个组。第Ⅲ组阳离子的分析方法甚多,Tenbusch等曾总结了13种分离法,但最常用的组内分离一般有两种方法即氨法和碱法。按氨法分离时,部分Mn~(2+)生成MnO(OH)_2而留在沉淀中,部分Co(OH)_2发生共沉淀,造成Mn_(2+),Co~(2+)两边跑,即一部分随Fe(OH)_3,Al(OH)_3,Cr(OH)_3共沉淀下来,一部分留在溶液中,使分离不完全,检出有一定困难。按碱法分离时,部分Zn(OH)_2被带下共沉淀,因而在检出时易丢Zn~(2+)。我们在近几年的实验课教学中,改进了阳离子第Ⅲ组组内分离条件。分离效果好,克服了碱法和氨法分离的缺点。 相似文献
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对乙酰基偶氮羧分光光度法测定铜锌镍及其化合物中的微量钙 总被引:1,自引:0,他引:1
本文提出在NaOH-NH_3·H_2O或NH_3·H_2O介质中,可采用Fe(OH)_3共沉淀法富集Cu、Zn、Ni及其化合物中的微量钙,用离心分离法分离基体元素后,再以对乙酰基偶氮羧光度法测定。方法分离手续简便,测定快速准确,标准加料回收试验的回收率在96—100.7%之间,试样分析的相对标准偏差<±3.2%(6—9次测定)。 相似文献
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采用混合酸直接消解样品,不分离析出的残渣硅元素,将残渣直接溶解到原液中,以电感耦合等离子体原子发射光谱(ICP-AES)法测定铝合金中高含量的硅,通过基体匹配法配制标准溶液系列,实验结果相对标准偏差小于0.3%,回收率在95%~105%,方法简化样品处理步骤,适用于快速高效地测定铝合金中高含量的硅。 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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Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields. 相似文献
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A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL. 相似文献
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A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions. 相似文献
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Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives. 相似文献
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The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion. 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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Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular SN2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively. 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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N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%). 相似文献