氧弹燃烧-离子选择性电极法测定氟

介绍了一种测定试样中氟含量的快速方法。首先利用氧弹燃烧技术对样品进行预处理,将氟转化为氟化氢,用碱液吸收燃烧产物,吸收液加入TISAB消除Al^3 、Fe^3 等离子干扰,调节溶液pH在5～8后进行定容,然后用氟离子选择性电极用标准加入法测定溶液的电位,从而测得样品中氟的含量。对香烟、头发和饲料进行分析,结果表明该法简单、快速、结果可靠,可用于试样中氟的快速测定     

高钒试样中钙镁的快速连续测定

高钒试样中钙的测定是在一定酸度条件下 ,在氯化铵存在下用草酸铵沉淀钙而与钒分离 ,然后用硫酸溶解 ,再用高锰酸钾标准溶液滴定 [1] 或将草酸钙灼烧为氧化钙后用 EDTA络合滴定 [2 ]。这些方法分析流程长 ,操作复杂 ,并且对高含量镁的测定均没有详细报道。本文提出了一种简便、快速测定高钒试样中高含量钙和镁的方法。在弱酸性时 ,以铝为载体 ,用铅盐分离钒酸根 ,六次甲基四胺 -铜试剂沉淀过量的 Pb( )、Al( )和干扰离子 ,于过滤后的同杯溶液中用 EDTA溶液滴定钙 ,用 Cy DTA溶液滴定镁。本文已用于大批量高钒试样中高含量钙和镁的测定…     

X射线荧光光谱法测定矿石中钨和钼

本文是研究矿石中常量钨和钼的同时测定。采用过氧化钠分解试样,柠檬酸溶液浸取熔块,使钨和钼成络合物状态保留在溶液中,再用磷酸酸化,然后采用散射线内标法进行X射线荧光光谱测定,取得了较满意的结果。方法快速,省试剂,适用于大批矿石试样中常量钨和钼的测定。     

顺丁橡胶分子结构参数对其浓溶液流变性质的影响

对顺丁橡胶浓溶液作了较为深入的研究,主要讨论了分子量分布和支化因子与顺丁橡胶浓溶液流动行为的关系。用倒沉淀分级的方法进行了大量分级,得到分子量分布较窄的试样;对这些试样用GPC-自动粘度计联用的方法测定了分子量、分子量分布和支化因子,同时用同轴圆筒式粘度计及落球方法测定了这些试样的浓溶液粘度。     

电感耦合等离子体发射光谱(ICP-OES)法测定含硼聚乙烯核屏蔽材料中的硼

含硼聚乙烯作为一种广泛应用的核屏蔽材料，准确掌握其中硼含量对于辐射防护屏蔽工程设计和屏蔽效果目标计算具有重要的意义。本文采用碳酸钠950 ℃熔融试样，以50%的盐酸溶液浸提熔融块，利用全程序空白试验溶液作为打底液配制校准系列曲线溶液作线性校准，建立了电感耦合等离子体发射光谱法（ICP-OES）测定含硼聚乙烯核屏蔽材料中硼量的方法。试样测试溶液与线性校准系列溶液中大量钠离子基体相匹配，有效消除试样溶液与工作曲线溶液因离子强度、黏度等物理因素引起的非光谱干扰对测定结果准确度的影响；选用15%的王水冲洗进样系统，有效消减了硼在测定过程中存在的记忆效应问题；测试不同含量水平的试样，方法精密度（RSD，n=6）为0.7%～1.6%；以方法比对和加标回收方式验证本方法的准确度，与化学容量滴定法分析测试结果无显著性差异，相对误差为-1.6%～1.9%；回收率为99.0%～102%。该方法操作简便，能够快速准确的为工艺生产、屏蔽工程设计计算等提供可靠的分析数据。     

土壤中铅、镉测定的试样预处理方法的改进

作为对GB/T 17140-1997中所列方法的改进,建议用混合酸(VHNO3 VH2O2 VHF=4 2 1)在微波消解仪中消解试样。微波消解的参数也进行了试验并确定了最佳条件,所得试样溶液蒸发至浆状并加盐酸溶解盐类,将试样中的Pb(Ⅱ)、Cd(Ⅱ)以碘化物络阴离子的形式萃取入4-甲基戊酮-2(MIBK)液层中,并在MIBK溶液中用火焰原子吸收光谱法测定铅及镉。试验结果表明:经改进的方法不仅有较高的精密度和准确度,而且操作简便且快速,算得两元素测定结果的相对标准偏差(n=10)均小于5%。测定铅和镉的回收率分别为99.2%和96.4%。     

铅基、锡基轴承合金及铅锡焊料中铅铜的快速测定

用邻菲绕啉掩蔽铜及少量铁、镍、锌等;用酒石酸掩蔽锡、锑,在 pH5—6微酸性溶液中以 EDTA 滴定铅。另取试液以铜试剂比色法测定铜。方法简便快速、终点敏锐、成本低、重现性好,适合试样中2—80%铅和0.3—6%铜的测定,10分钟内可完成一个试样中两元素的分析。试剂配制硝酸-酒石酸混合溶液:称取300克酒石酸,加少量水溶解后慢慢加入300毫升硝酸,以水稀释至1000毫升;0.3%邻菲绕啉溶液:0.3克试     

铬天青S光度法测定锌铝合金中铝

本文用盐酸及过氧化氢分解试样,在 pH5.5～5.8乙酸-乙酸钠缓冲溶液中,使铝与铬天青 S 形成紫红色络合物,进行光度测定。Fe~(3+)的干扰以抗坏血酸还原,基体锌的干扰可在标准中加入试样等量的锌加以克服,其它杂质元素不干扰测定。本法具有快速、准确的优点。主要试剂:乙酸-乙酸钠缓冲液:每升溶液中含300克无水乙酸钠和50毫升冰乙酸;锌溶液:称取     

铝硅钛合金中硅、铁、钛、铜、锰及镁的快速分析

本法使用经研究预先配制的元素显色液来代替分次加入试剂,从而避免了反复调节酸度及干扰元素的分离、过滤等手续;同时以一次处理的试样溶液用分光光度法测定多种合金元素。因此方法操作简易、快速、效率高。     

汞(Ⅱ)选择性吸附试纸的制备与应用

基于Hg~(2+)与聚烯丙基胺之间存在相互作用,以滤纸为基质,以聚烯丙基胺盐酸盐为原料制成了Hg(Ⅱ)选择性吸附试纸。用该试纸结合分光光度法测定试样溶液中Hg~(2+)含量,线性范围为0.1~50μmol/L,检测限为0.07μmol/L。测定30μmol/L Hg~(2+)试样溶液作重复性考察,7次测定相对标准偏差不超过3.5%。用本方法测定含Hg~(2+)试样,所得结果与冷原子吸收法没有明显差异。     

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.     

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.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

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%).