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研究了一种定容-氧气循环燃烧法测定捕收剂吸附量的方法,并与传统的溶剂萃取-分光光度法进行了比较。实验表明,定容-氧气循环燃烧法较溶剂萃取-分光光度法测定油酸钠在磷矿石表面的吸附量更简便,也更准确。 相似文献
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定容-氧气循环燃烧法测定捕收剂的吸附量 总被引:1,自引:0,他引:1
研究了一种定容-氧气循环燃烧法测定捕收剂吸附量的方法,并与传统的溶剂萃取-分光光度法进行了比较。实验表明,定容-氧气循环燃烧法较溶剂萃取-分光光度法测定油酸钠在磷矿石表面的吸附量更简便、准确。 相似文献
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分别采用紫外分光光度法测定二氢乳清酸(DHO)的减少量、PDAB显色法测定N-氨甲酰-天冬氨酸(CA-asp)的生成量来测定二氢乳清酸酶酶活,并对两种方法进行了比较。结果表明紫外分光光度法和PDAB显色法均有良好的回收率,分别为99.4%~101.2%、98.0%~101.3%。但由于PDAB显色法的检测范围为0.05~1.00g/L,较紫外法的检测范围0.05~0.30g/L更为宽泛,仪器要求低,便于实际操作。因此,采用PDAB显色法测定二氢乳清酸酶酶活较为方便。 相似文献
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采用滴定法、半中和法、p H法、电导率法、紫外分光光度法5种方法,测定了3,4-二硝基吡唑(DNP)和3-硝基-1,2,4-三唑-5-酮(NTO)两种钝感炸药的酸性解离常数p Ka,并对不同方法所测的结果进行比较和讨论。结果表明,滴定法、半中和法、紫外分光光度法3种方法适合DNP类物质的p Ka测定,实验结果基本一致,与文献值的相对误差RE5%;滴定法、p H法更适合NTO类物质的p Ka测定,实验结果基本一致,与文献值的相对误差RE4%。DNP的p Ka大于NTO的p Ka,即DNP比NTO的酸性弱,对设备等的腐蚀作用较小,更适宜用作熔铸炸药载体。根据这5种酸性解离常数测定方法的优缺点,讨论了测定不同性质物质的p Ka时可选用的方法。 相似文献
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《中国无机分析化学》2019,(6)
将新近实施用于测定地表水中石油类的紫外分光光度法与红外分光光度法的方法特性参数以及应用于各类实际水样测定进行比对研究。结果表明,两种方法的实际检出限均为0.004mg/L、测定下限均为0.016mg/L,加标回收样品紫外法测定结果相对标准偏差为4.2%~6.6%,加标回收率为82.0%~96.0%;红外法相对标准偏差为3.8%~5.5%,加标回收率为82.0%~97.0%,精密度和准确度等性能指标相近,在使用不同萃取方式应用于各种不同来源和组成水体的实际样品测定时,同种方法所得结果相对偏差均小于10%,但紫外分光光度法所得结果与红外分光光度法最大相对偏差达到了49.0%,并且红外分光光度法测定结果较之紫外分光光度法与样品理论浓度值更为接近,表明紫外分光光度法对较复杂水体石油类样品的测定存在局限性。 相似文献
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采用循环伏安法、微分脉冲伏安法、交流阻抗谱以及计时电流法等电化学方法,结合红外光谱、紫外-可见分光光度法、原子力显微镜、透射电子显微镜以及原子吸收光谱等辅助手段,表征了固定漆酶的聚苯胺-草酸钴纳米复合物的化学组成、结构和形貌,测试了纳米复合物固酶前后的导电性能的变化,研究了纳米复合物修饰电极上固定漆酶的直接电化学行为,评估了该电极的催化氧还原效能以及作为电化学传感器检测氧分子的性能。实验结果表明该电极在不含电子介体的溶液中以酶活性中心T2作为首要电子受体,将得到电子传递给化学吸附的氧气使其被电还原,其表观电子迁移速率为0.017 s~(-1),且具有良好的催化氧还原性能(氧还原起始电位:460 m V vs NHE,转化氧分子为水的表观速率常数为2.6×10-4 s~(-1)),酶电催化氧还原为水分子步骤为反应的速控步。该电极作为电化学传感器对氧具有极低检测限(0.20μmol·L~(-1)),宽线性响应范围(0.4~7.5μmol·L~(-1))以及对底物高亲和力(KM=122.4μmol·L~(-1))等优势。 相似文献
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金-钯双金属纳米颗粒修饰玻碳电极阳极溶出伏安法测定三价砷的方法研究 总被引:1,自引:0,他引:1
研究了金-钯双金属纳米颗粒修饰电极测定痕量砷的阳极溶出伏安法。采用紫外可见分光光度法、高分辨透射电镜及循环伏安法对颗粒的结构和电化学特性进行表征。采用方波伏安法测定三价砷,探讨了富集电位和方波伏安参数如频率、增幅、波幅以及干扰离子等对测定结果的影响。实验结果表明:金-钯双金属纳米颗粒呈壳-核结构;砷在0.30 V出现灵敏的阳极溶出伏安峰,峰电流与砷质量浓度在0.5~20μg/L范围内呈良好的线性关系,检出限为0.15μg/L;所制备的修饰电极重现性好,可用于三价砷的重复测定。共存离子Cu(Ⅱ)会影响三价砷的测定,而Pb(Ⅱ)、Cd(Ⅱ)、Zn(Ⅱ)等离子的存在对测定结果无影响。 相似文献
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An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions. 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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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
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An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction. 相似文献
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The Diels-Alder reactivity of 1,2-heteroborines (H4C4B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed. 相似文献
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Xi-Liu YunWen-Ying Bi Jian-Hui HuangYu Liu Daisy Zhang-NegrerieYun-Fei Du Kang Zhao 《Tetrahedron letters》2012,53(38):5076-5080
A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd2(dba)3-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring. 相似文献
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Shashikant U. Dighe Surya K. Samanta Shivalinga Kolle Sanjay Batra 《Tetrahedron》2017,73(17):2455-2467
An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y1 and Y2. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones. 相似文献
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In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates. 相似文献
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Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles. 相似文献