紫外法COD在线监测仪的性能分析和量值溯源

目前JJG 1012–2006《化学需氧量(COD)在线监测仪》计量检定规程只适用于采用强氧化剂氧化消解方式和电化学原理设计的COD在线监测仪的量值溯源,不适用于紫外法COD在线监测仪的量值溯源。因此通过比较分析现行COD在线监测仪的国家标准、行业标准和计量检定规程,提出了紫外法COD在线监测仪的性能评价和量值溯源方法并进行实验验证,为该类型仪器的标准化性能评价方法及检定规程的制修订提供了参考。     

实验室认可量值溯源中几个问题的探讨

介绍量值溯源的含义,总结实验室量值溯源中常见的几个问题,提出了保证量值溯源有效性的措施和建议。     

化学测量溯源性的探讨

结合化学测量的特点，探讨了实现化学测量量值溯源性的若干问题，主要有实现化学测量量值溯源性的由来、现有的技术基础、溯源性的基本设想及相关的几个问题。     

实现标准物质量值溯源性的初步探讨

叙述了研究标准物质量值溯源性的必要性，讨论了实现标准物质值溯源性的基本途径及技术难点。指出了量值溯源的关键是对定值方法和分析过程质量保证技术进行系统的研究。     

实现标准物质量值溯源性的初步探讨

叙述了研究标准物质量值溯源性的必要性,讨论了实现标准物质量值溯源性的基本途径及技术难点。指出了量值溯源的关键是对定值方法和分析过程质量保证技术进行系统的研究。     

环境监测仪器设备量值溯源结果的确认

<正>环境监测仪器设备的量值溯源方式一般有计量检定和计量校准[1]。目前许多实验室工作人员计量知识缺乏,对仪器设备量值溯源的重要性认识不足,导致对仪器设备量值溯源结果的确认流于形式,使得计量机构对仪器设备的量值溯源结果未能在实际工作中得到正     

化学测量溯源性的探讨

结合化学测量的特点,探讨了实现化学测量量值溯源性的若干问题,主要有实现化学测量量值溯源性的由来、现有的技术基础、溯源性的基本设想及相关的几个问题。     

标准物质的作用

标准物质作为具有准确量值的计量标准 ,是化学计量的重要组成部分和量值传递与溯源的一种重要手段 ,广泛应用于国民经济和社会发展的各个方面 .其主要作用在于 :1　保存和传递特性量值 ,建立测量溯源性　　标准物质是特性量值准确、均匀性和稳定性良好的计量标准 ,具有在时间上保持特性量值 ,在空间上传递量值的功能 .通过使用标准物质 ,可以使实际测量结果获得量值溯源性 .2　保证测量结果的一致性、可比性通过校准测量仪器 ,评价测量过程 ,由标准物质将测量结果溯源到国际单位 (ＳＩ)制 ,保证测量结果的一致性、可比性 ,从而达到量值统一 …     

浅谈蛋白质含量量值溯源传递体系的构建

简述了蛋白质含量测定结果溯源到SI单位的重要性,结合中国计量科学研究院开展的工作及当前国际蛋白质计量发展的趋势,阐述了实现蛋白质含量测定结果溯源到SI单位的两种方案,方案中蛋白质标准物质的定值结果可以通过同位素稀释质谱法、滴定法、凝固点下降法等权威计量方法最终与SI单位连接,因此保证了蛋白质标准物质定值结果的准确和可溯源.以蛋白质标准物质作为量值的载体,可实现蛋白质含量量值在应用领域的传递,从而构建起蛋白质含量量值溯源和传递体系.     

化学计量研究进展

叙述了化学计量的特点、作用和重要性及其研究内容,探讨了标准物质量值传递系统及实现标准物质量值溯源性的途径,阐述了建立化学测量溯源性的重要性、困难性、复杂性及基本设想和途径,并对化学计量中物质的量“摩尔”进行了简要论述。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

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%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

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.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

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.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

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.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

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 S_N2 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.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

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.