氢化物连续发生等离子体原子发射光谱法测定氟石中痕量砷

将氢化物连续发生等离子体原子发射光谱(CF HG ICP AES)联用技术应用于氟石中痕量砷的测定,对方法的工作参数进行了试验,方法的线性范围为0.005 0~0.100 0 mg·L-1,检出限为0.8 g·L-1,回收率为95%,RSD为5.0%。     

微柱分离-ICP-MS测定高纯氧化钐中稀土杂质

研究了微柱分离 ICP MS测定高纯氧化钐中痕量Dy,Ho,Er,Tm的方法,方法基于采用Cyanex272负载树脂微柱,选定上述杂质与大量基体分离的实验条件,分离周期为32min。最终建立了微柱分离Sm后测定Dy,Ho,Er,Tm,其他稀土杂质用内标补偿ICP MS法直接测定的分析方法。方法测定下限为0.1～5.0μg·g-1,加标回收率为90%～115%,相对标准偏差为0.9%～5.1%。本法可满足快速测定99.999%氧化钐中14个稀土杂质的要求。     

钛及钛合金中钇的AAS法测定

钛及钛合金中杂质钇量的测定,有采用PMBP苯萃取偶氮胂Ⅲ比色法、离子交换分离分光光度法等,其结果都是以钇为代表的稀土总量,不能满足单一稀土钇量测定的要求。ICP原子发射光谱可测得单一钇量,但需分离后采用昂贵的ICP 发射光谱仪。本文采用氢氟酸溶样后,用氟化钙沉积钇,使基体钛和其存元素得到分离,钇得到富集,达到火焰原子吸收法(火焰AAS法)测定钇的灵敏度,用氧化二氮-     

原子发射光谱法测定混合稀土中氧化铕

随着现代科学技术的发展,人们对稀土的认识不断增强,对稀土的研究、应用日益广泛,稀土元素的分析已成为分析化学一个很重要的分支,因此对它的测定有其现实意义。由于稀土元素之间的化学性质极为相似,用一般的化学分析方法测定比较困难。虽然氧化铕的测定已有报道,但是它只是作为高纯物质或者杂质元素应用ICP光谱进行分析,对混合稀土中氧化铕的分析,主要以X—荧光分析为主,但仪器价格昂贵,较难普及。本文应用原子发射光谱分析法,选择最佳载体及最佳操作,以钪为内标,光谱法测定混合稀土中氧化铕。     

高纯氧化钪中痕量稀土元素的电感耦合等离子体原子发射光谱分析和稀土元素间的光谱干扰及其校正

本文提出了用 ICP-AES 直接同时测定高纯氧化钪中15个痕量稀士元素的新方法。用PGS-2光栅光谱仪,Plasma Therm ICP-5000D 光源系统,乙醇预去溶进样方式,直接同时测定纯度为99.995%的高纯氧化钪中15个痕量稀土杂质元素,并讨论了稀土元素间的干扰及某些元素的光谱干扰的校正。当样品溶液中稀土总浓度为5mg/ml:时,测定下限为镧、钆、钬和铥0.0002%,镨、钕、铽和镥0.0004%,铕、镝、铒和钇0.0001%、镱0.00004%,铈和钐0.001%。其相对标准偏差为1.7～8.2%。     

高纯氧化铈中14个稀土元素杂质的光谱测定

高纯稀土氧化物的应用日趋广泛,由于工艺的完善,要求检出限越来越低。对稀土元素杂质总量小于0.01％的高纯稀土氧化物多采用化学光谱法测定。直接光谱和控制气氛光谱法测定氧化铈国内外已有报导。报导直流电弧粉末法测定镧、镨、钕、钐和钇下限总和为0.05％;控制气氛法测定上述五元素的下限总和为0.022％;国外以控制气氛法在GE-340光谱仪上摄谱测定14个稀土元素杂质下限总和为0.0216％。由于铈是光谱线最复杂的元素之一,加之电流较大,背景深,许多灵敏线受基体扩散影响和干扰。本工作在氧-氩气氛中以直流电弧粉末法测定14个稀土元素杂质,对分析线进行了细致的选择,对电极形状     

三重四极杆电感耦合等离子体质谱(ICP-MS)法测定氧化铕中13种稀土杂质元素

稀土杂质元素直接影响高纯单金属稀土材料的整体性能,是高科技领域许多材料的重要组成部分。通过考察最佳的消解酸量、温度、时间、氧气反应气流量、稀释气流量,建立了基于三重四极杆电感耦合等离子体质谱仪(ICP-MS/MS)直接测定氧化铕中13种稀土杂质元素分析方法。该方法采用0.1%基体直接进样,可以很大程度提高前处理分析效率。利用碰撞模式测定氧化铕稀土中的Y、La、Pr、Nd、Sm、Gd、Tb、Dy、Ho、Er、Yb、Lu元素,氧气质量转移模式测定氧化铕中的Tm,两种模式结合可以有效去除多原子干扰,实现氧化铕的稳定测试分析。通过对氧化铕标准物质（GBW02902）直接测定分析,结果表明,在碰撞和氧气质量转移模式下,各元素线性相关系数（r）均大于 0.9999,方法检出限为0.001~0.023 mg/kg,测试精密度优于1.99%,13种元素的测试值都在认定值的不确定度范围之内。该分析方法操作简单,测试稳定,效率高,为实验室进行氧化铕材料中REE杂质的准确测试分析提供思路和借鉴。     

以 N_2作冷却气的小功率 ICP 发射光谱法测定钛合金中钼、钒、铬、铝、铁和钇

Ar-ICP发射光谱法测定合金成分和杂质元素以及有关N_2/Ar ICP光源研究已见诸报导。本文提出以N_2作冷却气的小功率低气流ICP-发射光谱法测定钛合金中六个元素。通过实验选定了N_2冷却ICP的最佳工作条件,进行了钛合金基体干扰,溶液酸度,K~+、NH_4~+离子对分析线的影响试验。本方法用一次溶样同时测定钛合金中四种合金成分钼、钒、铬、铝和两种杂质元素铁及钇。相对标准偏差合金成分元素为1.48～2.21％;杂质元素为3.8～6.0％。     

微型柱分离-ICP-MS法测定高纯氧化铽中14个稀土杂质元素

研究了微型柱分离 电感耦合等离子质谱法(ICP MS)测定高纯Tb4O7中痕量Lu的方法,采用Cyanex272负载树脂微型分离柱,选定了分离大量Tb4O7基体的实验条件,分离周期为40min。建立了微型柱分离Tb后测定Lu以及内标补偿法直接测定其它稀土杂质的高纯Tb4O7中14个稀土杂质元素的ICP MS分析方法。方法检出限为0.003～0.10μg g,加标回收率为86.6%～114%,相对标准偏差为1.1%～18%。方法可满足快速测定99.999%Tb4O7中14个稀土杂质元素的要求。     

ICP—AES光谱测量高纯镧氧化物中非稀土杂质

报道了用HPLC与ICP－AES联用测定高纯氧化镧中痕量非稀土杂质的新方法。应用P507树脂柱作固定相和稀硝酸作流动相，研究了基体（La)和非稀土杂质的色谱保留行为。发现使用pH1.7的硝酸可以有效地从HPLC柱上淋洗非稀土杂质。实验结果表明，可以在15min内实现基体与待测元素之间的有效分离。本法已应用于高纯La2O3中8个非稀土杂质的定量测定，其回收率在90％－110％之间。     

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.     

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.     

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.     

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.     

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.     

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.     

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.