二次微分简易示波伏安法直接测定酒样中半胱氨酸

在 0 .2mol·L- 1NaOH支持电解质溶液中 ,半胱氨酸在二次微分简易示波伏安图阴极支- 0 .4 9V(vs .SCE)处产生一灵敏的峰 ,研究了半胱氨酸在此底液中的示波伏安行为 ,并据上述示波特性建立了二次微分简易示波伏安法直接测定酒中半胱氨酸含量的新方法。校正曲线的线性范围为 3.0× 10 - 6 ～ 5 .0× 10 - 5mol·L- 1,相关系数为 0 .9995 ,检出限为 1× 10 - 6 mol·L- 1,对 1.0×10 - 5mol·L- 1半胱氨酸进行 6次测定的RSD为 1.8%。利用此法测定了啤酒、黄酒及加饭酒中半胱氨酸的含量 ,样品的回收率分别为 94 .2 %、10 1.6 %和 10 2 .2 %。方法具有仪器装置简单、经济 ,方法简便快速、无需通氮除氧以及对样品进行前处理的优点     

β-环糊精-二次微分简易示波伏安法测定苯巴比妥

在NaOH底液中 ,β 环糊精能够产生灵敏切口 ,且该切口深度随苯巴比妥 β 环糊精包结物量的增加而变浅。根据 β 环糊精的示波特性 ,建立了用二次微分简易示波伏安法间接测定苯巴比妥注射液中苯巴比妥含量的新方法。苯巴比妥的浓度在 2 .5× 10 - 6 ～ 4 .5× 10 - 5mol·L- 1范围内的回归方程为h(V) =4 .5 5 9- 1.381× 10 4 c(mol·L- 1) ,相关系数为 - 0 .9976 ,检出限为 1.5×10 - 6 mol·L- 1。对于 2 .5× 10 - 5mol·L- 1苯巴比妥 5次测定的相对标准偏差为 2 .7% ,回收率为10 2 .1%。与高效液相色谱和其他方法相比 ,此法具仪器简单、简便快速、无需通氮除氧等特点     

钴-锌试剂络合吸附伏安法测定中草药中钴

研究了测定痕量钴的一种灵敏的吸附伏安法 ,利用钴和锌试剂络合物在悬汞电极上的吸附性 ,有效地提高了分析的灵敏度。在 0 .0 0 5mol·L-1NH3 和 0 .0 6mol·L-1NH4Cl及 2 .5× 1 0 -6mol·L-1锌试剂底液条件下 ,该体系 1 .5 ,2 .5阶微分吸附伏安法测定钴的线性范围为 1× 1 0 -10 ～ 1× 1 0 -7mol·L-1,用 2 .5阶微分吸附伏安法 ,富集 3min的检出限为 5× 1 0 -11mol·L-1。用此法直接测定了中草药中痕量钴     

普鲁士兰修饰碳黑微电极同时微分伏安法测定多巴胺和抗坏血酸

将含有1.0%普鲁士蓝的碳黑与固体石蜡按2.5∶1(质量比)混合后装入φ0.2mm的石英毛细管中,在其上端插入一铂丝并抛光后即制成普鲁士蓝修饰碳黑微电极.对多巴胺(DA)及抗坏血酸(VC)在此电极上的电化学行为及应用此电极测定两组分的最佳条件进行了研究,在定量测定中采用二次微分线性扫描伏安法.在最佳条件下,DA与VC的峰电流(i″p)分别与各自的浓度保持如下线性关系DA为4.0×10-6～8.0×10-4mol·L-1,VC为6.0×10-5～1.0×10-3mol·L-1;检出限(3σ)依次为2.0×10-6mol·L-1及1.0×10-5mol·L-1.应用此方法分析了3种含DA及VC的混合溶液,测得结果的相对标准偏差(n=8)依次小于2.0%及3.0%,回收率范围依次为96.5%～101.0%及95.0%～102.5%.     

溶出伏安法对维生素K3的研究与测定

应用微分脉冲溶出伏安法(DPSV)对维生素K3在玻碳电极(GCE)上的电化学行为进行了研究.在氨水-NH4Cl(pH 9.0)底液中,对维生素K3进行循环伏安扫描,发现有一对良好的氧化还原峰出现,对电极反应机理进行了探讨.阴极溶出伏安峰电流与其浓度在2.0×10-6～1.0×10-4mol·L-1范围内呈线性关系(r=0.998 5),检出限为4.0×10-7mol·L-1.对于1.0×10-5mol·L-1的维生素K3,平行7次测定结果的RSD为1.15%.应用此方法对亚硫酸氢钠甲萘醌注射液进行了测定,方法的回收率为97.3%～102.5%.     

催化氢波-单扫描示波极谱法测定克拉霉素

建立一种灵敏快速测定克拉霉素的新方法。在 0. 24 mol·L-1 KH2PO4 Na2HPO4(pH 6.81)支持电解质中,克拉霉素于-1.57 V(vs.SCE)处产生一催化氢波,其二阶导数峰峰电流与克拉霉素浓度在2.0×10-6~ 1.6×10-4mol·L-1范围内呈线性关系(r=0.999 4,n=8),检出限为1.0×10-6 mol·L-1。10 次测定 1. 0×10-5 mol·L-1 克拉霉素峰电流相对标准偏差为1 8%,回收率在98.3%~100.6%之间。该方法可用于药剂中克拉霉素的测定。     

硫代硫酸根的溶出伏安吸附性质及应用

在 0 .0 1mol·L-1LiNO3介质中 (pH 2 .70 )S2 O32 -有一灵敏的阴极溶出峰( - 0 .42V) ,其峰电流与S2 O32 -浓度在 1× 1 0 -7mol·L-1～ 4× 1 0 -6mol·L-1范围内有线性关系。当富集 2 0 0s时 ,检测限可达 5× 1 0 -8mol·L-1。溶出峰具有吸附性质 ,在悬汞电极上的吸附符合Frumkin等温式。测得在悬汞电极上的饱和吸附量为 1 .0 3× 1 0 -9mol·cm-2 。该方法用于PbS2 O3溶度积的测定 ,结果与文献值基本一致。     

痕量雌二醇的吸附方波伏安法检测

本文报道一种简便、快速、灵敏检测痕量雌激素的吸附溶出方波伏安法。该法先将雌二醇在玻碳电极上吸附富集一定时间 ,然后以方波伏安溶出法检测其氧化电流。介质为含有 8× 1 0 - 5mol· L- 1溴化十六烷基三甲铵 ( CTAB)的 0 .1 mol· L- 1磷酸盐缓冲溶液 ( p H=1 0 .0 )。该法检出限为 5× 1 0 - 8mol· L- 1,线性范围为 5 .2× 1 0 - 7～ 5× 1 0 - 5mol· L- 1。研究了雌二醇的电极反应机理     

方波吸附溶出伏安法同时测定水中痕量铜和镉

报道了应用方波吸附溶出伏安法 (OSWSV)同时测定Cu(Ⅱ )和Cd(Ⅱ )。在 0 .0 1mol·L- 1酒石酸钾钠 2 .0× 10 - 4mol·L- 1水杨醛肟溶液中 (pH 11.75 ) ,Cu(Ⅱ )和Cd(Ⅱ )分别与水杨醛肟形成的络合物均产生非常灵敏的还原波 ,峰电位分别为 - 0 .5 5 6V和 - 0 .70 4V (vs.Ag/AgCl以下均同 )。峰电流与Cu(Ⅱ )、Cd(Ⅱ )浓度分别在 9.0× 10 - 74 .0× 10 - 8mol·L- 1和 2 .0× 10 - 6 6 .0×10 - 8mol·L- 1范围内呈线性关系 ,检出限均为 1.0× 10 - 8mol·L- 1。该法用于同时测定水样中痕量Cu(Ⅱ )和Cd(Ⅱ ) ,所得结果满意。通过对该体系的初步研究 ,Cu(Ⅱ )、Cd(Ⅱ )与水杨醛肟形成的络合物的还原峰具有明显的吸附性。     

表面活性剂增敏2.5次微分极谱测定香豆素

拟定了表面活性剂增敏、2 .5次微分极谱测定香豆素的方法。在含 6.0× 10 -6 mol·L-13 氯 2 羟丙基 三甲基氯化铵的 0 .1mol·L-1KH2 PO4 Na2 HPO4 (pH 6.8)缓冲液中 ,香豆素还原波 [峰电位Ep=- 1.60V(vs .SCE) ]的 2 .5次微分极谱峰峰电流e″p 与其浓度在 4 .0× 10 -7～ 6.0× 10 -5mol·L-1范围内呈良好线性关系 (r =0 .9998,n =10 ) ,检出限为 1.2× 10 -7mol·L-1。 13次平行测量 8.0× 10 -6 mol·L-1香豆素的峰电流 ,RSD为 1.5 %。该方法可用于中药白芷中香豆素的直接测定     

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%.     

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.     

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%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

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.     

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

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.     

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.