碳糊电极阳极溶出伏安法测定痕量铋(Ⅲ)

在 0 .2mol·L-1盐酸底液中 ,铋 (Ⅲ )与桑色素所形成的铋 (Ⅲ ) 桑色素络合物吸附于碳糊电极上 ,在 0 .30V(vs.SCE)预富集后 ,在 - 0 .30V处静止还原 30s ,再从 - 0 .30V到 0 .30V进行阳极化扫描 ,在 - 0 .0 8V左右获得一灵敏的铋溶出峰 ,其二次导数峰电流与铋 (Ⅲ )浓度在 2 .0× 10 -9～6 .0× 10 -6mol·L-1范围内呈线性关系 ,检出限达 1.0× 10 -9mol·L-1。探讨了电极反应机理 ,方法应用于胃药和锰盐中铋的测定 ,结果满意     

单扫示波极谱法同时测定钴与镍

在 pH 9.70的Na2 CO3 NaHCO3、亚硝基红盐和氯代十四烷基吡啶体系中 ,镍和钴均有灵敏的络合物吸附波 ,其二阶导数峰电位分别为 - 0 .6 4V (vs .SCE) (镍 )和 - 0 .80V (vs .SCE)(钴 ) ,电流峰高与浓度在 3.4× 10 - 9～ 3.74× 10 - 6 mol·L- 1(镍 )和 7.0× 10 - 11～ 6 .0× 10 - 6 mol·L- 1(钴 )范围内呈线性关系 ,检出限分别为 2 .4× 10 - 9mol·L- 1(14 1ng·L- 1镍 )和 3.2× 10 - 11mol·L- 1(1.9ng·L- 1钴 )。方法应用于水样和生物样品中微量钴和镍的测定 ,结果满意     

桑色素修饰碳糊电极吸附溶出伏安法测定人尿中痕量铅

制作了用桑色素作修饰剂的碳糊修饰电极 ,利用该电极为工作电极 ,建立了测定痕量铅的新方法。在甲酸钠 盐酸缓冲溶液 (pH 4 .9)中 ,在 - 0 .10V(vs .SCE)下搅拌富集 ,铅 (Ⅱ )与化学修饰碳糊电极表面的桑色素形成电活性络合物而吸附富集于电极表面 ,经 - 0 .85V(vs.SCE)静止还原后 ,阳极化线性扫描 ,在 - 0 .4 3V(vs .SCE)获得一灵敏的二次导数溶出峰。在最佳条件下分别富集 360s和 180s ,其二次导数峰电流与铅 (Ⅱ )浓度分别在 5 .0× 10 - 9～ 1.0× 10 - 7mol·L- 1和 2 0×10 - 8～ 1.0× 10 - 6 mol·L- 1两个范围内呈良好的线性关系 ,富集 6min ,检出限可达 1.0× 10 - 9mol·L- 1(S/N =3)。同时 ,探讨了电极反应机理。方法应用于尿铅测定 ,获得满意的结果     

茜素紫修饰碳糊电极吸附阳极溶出伏安法测定痕量锑的研究

报道了采用茜素紫修饰碳糊电极测定痕量锑的阳极溶出伏安法。在 0 .0 3mol·L- 1邻苯二甲酸氢钾 盐酸缓冲溶液 (pH 2 .4 )中 ,通过开路富集 ,Sb(Ⅲ )与茜素紫形成络合物而富集于电极表面 ,然后交换介质至 0 .6mol·L- 1盐酸中 ,于 - 0 .6 0V还原后再进行阳极化扫描 ,于 - 0 .50V左右获得一灵敏的锑的溶出峰 ,二次导数峰电流与Sb(Ⅲ )的浓度在 4 .1× 10 - 9～ 2 .9× 10 - 7mol·L- 1范围内呈线性关系 ,检出限达 1.6× 10 - 9mol·L- 1。方法应用于水样中锑的测定 ,结果满意     

邻苯三酚红修饰碳糊电极吸附伏安法测定痕量铜

报道了采用邻苯三酚红修饰碳糊电极测定痕量铜的方法。通过在邻苯二甲酸氢钾 -氢氧化钠 (p H4.5)介质中富集 ,Cu2 +和邻苯三酚红形成络合物富集于电极表面 ,然后转换到 0 .0 50 mol· L-1的 H3PO4 中 ,经阴极还原后再进行阳极溶出伏安法测定。Cu2 +浓度在 1 .6× 1 0 -9～ 2 .8× 1 0 -7mol·L-1范围内与二次导数峰电流呈线性关系 ,检出限达 8× 1 0 -10 mol·L-1。同时 ,对电极反应机理进行了探讨。应用于合金样的测定 ,取得满意的结果。     

改性蒙脱土中钴交换量的示波极谱法测定

在pH 7．6的三(羟乙基)胺(TEA)缓冲介质中,用单扫描示波极谱法测得由混配络合物Co2+·(DMGX)2·(NO2-)2所给出的灵敏还原极谱波,其峰电位在-1．07 V(vs．SCE)。峰电位与钴(Ⅱ)浓度在2．2×10-9-6．6×10-6mol·L-1之间呈线性关系(相关系数为0．999 7),其检出限为7．4×10-10mol·L-1Co2+。研究了电极反应的机理并证明该极谱波为由上文提到的三元混配络合物所给出的吸附催化波。     

钒-5-溴水杨基荧光酮-氯酸盐体系极谱催化波的研究

在pH4.1的乙酸盐缓冲底液中,钒能与5-溴水杨基荧光酮形成络合物,并吸附在汞电极上,在氯酸盐存在下,在V(Ⅴ)的电极还原过程中形成催化波。用单扫二阶导数极谱法测定时,钒浓度在L.0×10-8～1.0×10-6mol·L-1范围内与峰高成正比关系,检出限为5.0×10-9mol·L-1。测得电活性络合物的组成为V(Ⅴ)5-Br-SAF＝11。平行催化反应的速率常数k=1.9×103(mol·L-1)-1·s-1。     

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     

半微分阳极溶出伏安法测定矿泉水中痕量铝

利用铝(Ⅲ)与8 羟基喹啉形成络合物的反应,用半微分阳极溶出伏安法进行水样中痕量铝(Ⅲ)的测定。以0.024moL·L-1乙酸 乙酸胺缓冲液(pH6.0)为底液,玻碳电极为工作电极,测得络合物的氧化峰电位是0.87V(vs.Ag/AgCl,饱和KCl)。峰高与铝(Ⅲ)浓度在1.00×10-5～5.00×10-5mol·L-1、8.00×10-8～4.00×10-6mol·L-1范围内呈良好的线性关系,铝的检出限为1.00×10-8mol·L-1。此法干扰较少,易于掩蔽,重复性好,灵敏度较高,用于矿泉水中微量铝(Ⅲ)的测定,获得满意效果。     

肌红蛋白在磷脂-月桂酸修饰的玻碳电极上的电化学行为及其分析应用

报道了肌红蛋白(Mb)在磷脂、月桂酸修饰的玻碳电极上的电化学行为 ,在 +0.2～ -0.7V(vs.Ag/AgCl)电位范围内 ,于pH6.0的0.01mol·L-1的KH2PO4、Na2HPO4底液中 ,肌红蛋白产生不可逆的还原电流峰 ;还原峰电流与肌红蛋白浓度在2.25×10-8 ～1.40×10-6 mol·L-1 范围内呈良好线性关系 ;线性回归方程为Ip(μA)=-0.01419 +0.2382cMb(10 -7mol·L -1) ,线性回归系数r(10)为0.998 ,检出限为1.20×10 -8mol·L -1,该电极可作为检测肌红蛋白的新型的高灵敏度电化学生物传感器。     

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.     

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.     

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.     

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.     

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.     

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.