四种阴离子的毛细管电泳电导检测(英文)

 采用柠檬酸 柠檬酸钠作为缓冲体系 ,使用负高压 ,对Cl-,NO3 -,HCO3 -和H2 PO4 -等 4种常见阴离子进行了分离检测 ,研究了缓冲剂的种类、浓度、pH值及操作电压对分离的影响。在选定的条件下 ,4种离子的定量线性范围 :Cl-5 0× 10 -5mol/L～ 2 5× 10 -3 mol/L ,NO3 -6 0× 10 -5mol/L～ 2 0× 10 -3 mol/L ,HCO3 -5 0× 10 -6mol/L～ 2 0× 10 -4 mol/L ,H2 PO4 -6 0× 10 -5mol/L～ 1 0× 10 -3 mol/L ;检出限 :Cl-1 5× 10 -5mol/L ,NO3 -3 0×10 -5mol/L ,HCO3 -1 0× 10 -6mol/L ,H2 PO4 -2 0× 10 -5mol/L ;峰面积的RSD (n =6 ) :Cl-3 1% ,     

金属-配位体缓冲溶液流动注射络合滴定铅(Ⅱ)

应用金属 -配位体缓冲溶液流动注射络合滴定法原理 ,研究了以 Pb2 + -NTA (氨三乙酸 )组成的缓冲溶液和二甲酚橙作为指示剂流动注射络合滴定Pb2 + 的条件 ,提出了选择最佳测定 p H值的方法。在选定条件下 ,Pb2 + 的最低检出浓度为 2 .4× 1 0 - 6 mol/L ,线性范围为 1 .0× 1 0 - 5～ 1 .2× 1 0 - 4mol/L ,相对标准偏差为 2 .0 % ,采样频率为 1 2 0次 /h。     

苯噻草胺的极谱特性研究

在 p H3.4 H3PO4-Na H2 PO4缓冲溶液中 ,苯噻草胺在 -1 .1 0 V左右产生一灵敏示波极谱波 ,利用此波可测定微量苯噻草胺 ,线性范围为 3.0× 1 0 - 8～ 2 .0× 1 0 - 5 mol/L,检出限为 1 .8× 1 0 - 8mol/L。     

离子缔合物-萃取荧光光度法测定水中阴离子表面活性剂

在 0 .2 5 mol/L H2 SO4 溶液中 ,罗丹明 B与阴离子表面活性剂形成离子缔合物 ,氯仿萃取后 ,于 5 5 0 nm处激发 ,荧光波长为 60 0 nm,对于十二烷基硫酸钠的线性范围为 0 .0 2 5～ 0 .4mg/L,RSD<2 .6%。方法可用于河水及生活废水中 1 0 -7～ 1 0 -6mol/L 阴离子表面活性剂的测定     

汞膜电极上N-乙酰-L-半胱氨酸的电化学行为

研究了汞膜电极上N 乙酰 L 半胱氨酸 (C5H8O3 SH ,NAC)的电化学行为和测定方法。在 0 .1mol LHAc NaAc缓冲溶液 (pH =4 .5 )介质中 ,方波伏安扫描于～ -0 .2 5V(vs.Ag AgCl)处出现一灵敏的阴极还原峰 ,用循环伏安法、线性扫描极谱法和脉冲极谱法等手段研究了体系的电化学行为及其反应机理。实验表明 :该峰具有明显吸附性 ,吸附分子为Hg2 (C5H8O3 S) 2 ,电子转移系数α为 0 .82 ,电子转移数为 1。NAC的浓度在1 2×1 0 - 8～ 5 .0× 1 0 - 6 mol L范围与其方波伏安峰高有良好的线性关系。方法的检出限为 5 .0× 1 0 - 9mol L ,用于富露施颗粒剂中NAC含量的测定 ,结果满意     

乙基罗凡明B指示反应动力学光度法测定痕量铱

提出了动力学光度法测定铱。在磷酸 -氯化钠介质中 ,Ir( )催化高碘酸钾氧化乙基罗丹明 B( ERB)形成褪色化合物 ,适宜条件为 c Na Cl=0 .0 2 mol/ L ,c H3PO4 =0 .1 0 mol/ L ,c KIO4 =2 .0× 1 0 - 3mol/ L ,c ERB=1 .7× 1 0 - 5mol/ L ,I=0 .0 2 ,90℃。铱浓度在 0 .4～ 32μg/L范围校正曲线成直线 ,检出限为 4.0× 1 0 - 10 g/ m L,对 2 0 μg/ L铱测定 1 1次的 RSD为1 .55% ,体系至少稳定 8h。考察了 30多种共存离子的影响。本法满意地用于某些冶金产品和矿石中铱的测定。铱催化反应对 Ir( )、ERB、KIO4 和 H3PO4 均为一级反应 ,表观活化能为 75.82 k J/ mol,探讨了反应机理     

长链S-烷基双硫腙为载体的碳酸氢根离子电极

以溴化S 十六烷基双硫腙载体制备了碳酸氢根离子选择性电极 ,选择性次序为 :ClO-4 >SCN->I-～HCO-3 >ClO-3 ～NO-3 >Ac->NO-2 >Cl->H2 PO-4 >SO2 -4 。膜配比 (质量百分比 )为溴化S 十六烷基双硫腙 (SHDTZ)·HCO-3 ∶邻苯二甲酸二异辛酯∶PVC =2 .5∶65.0∶32 .5电极性能最佳。 32℃时 ,在pH 8 30 .1mol/L三乙醇胺 硫酸缓冲溶液中 ,HCO-3 离子浓度在 1 .0× 1 0 -2 ～ 1× 1 0 -5mol/L范围与电极电位呈线性响应 ,检测限为 5.0× 1 0 -6mol/L;斜率为 54± 2mV/decade。研究了HCO-3 离子与载体的作用机理。用该法测定了人体血清中HCO-3 ,结果与滴定法一致。     

磷钼杂多酸光度法测定吲哚乙酸

研究了吲哚乙酸与磷钼杂多酸在浓度为 0 .0 3 mol/L的硫酸介质中发生氧化还原反应 ,形成的还原产物 (钼蓝 )在 NH3-NH4Cl缓冲溶液 (p H8.4)中最大吸收波长为 314 nm,表观摩尔吸光系数 ε值为 3.5 4× 10 4L· mol-1·cm-1 ,吲哚乙酸含量在 5 .0× 10 -7～ 5 .0× 10 -5 mol/L范围内符合比尔定律 ,检出限为 1.0× 10 -7mol/L,对 2 .0 0× 10 -5 mol/L吲哚乙酸测定 10次的相对标准偏差为 6 .42 % ,加标回收率为 94.2 %～ 10 0 .1%     

L-酪氨酸-高锰酸钾-硫酸化学发光体系研究

在硫酸介质中 ,L -酪氨酸与高锰酸钾反应能产生较强的化学发光 ,据此建立了测定 L -酪氨酸的分析方法。该法线性范围为 4.0× 1 0 - 6 ～ 2 .8× 1 0 - 5mol/L;检出限为 8.8× 1 0 - 7mol/L;对 1 .0× 1 0 - 5mol/L 的 L-酪氨酸进行连续1 0次平行测定 ,相对标准偏差为 2 .7%。该法已应用于测定医用氨基酸注射液中的 L-酪氨酸。     

抗坏血酸在2-氨基吡啶修饰电极上的电催化氧化及其应用

研究了 2 -氨基吡啶聚合膜修饰玻碳电极的制备及其电化学性质 ,修饰电极对抗坏血酸 ( AA)的氧化有明显的催化作用 ,其氧化电位负移 2 72 m V。在 p H5 .7的B.R.缓冲溶液中 ,以 1 5 0 m V为工作电位 ,AA在修饰电极上的响应电流与 AA的浓度在 4× 1 0 - 6～ 1 0 - 3 mol/ L范围内呈良好的线性关系 ,检出限为 1 .3× 1 0 - 6mol/ L。在此条件下 ,多巴胺 ( DA)对 AA无干扰 ,电极重现性良好 ,可用于实际样品中 AA的测定     

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.