纳米二氧化铈修饰碳糊电极线性扫描伏安法测定苯酚

在0.01mol.L-1硼砂溶液(pH 9.18)中,用纳米二氧化铈修饰碳糊电极作为工作电极,线性扫描伏安法测定苯酚。伏安图上出现一灵敏的氧化峰,其峰电位为+0.56V(vs.SCE),峰电流与苯酚的浓度在1.0×10-7～2.0×10-4 mol.L-1范围内呈线性关系,检出限(3s/k)为5.0×10-8 mol.L-1。富集时间为30s,同时采用线性扫描伏安法研究苯酚在纳米二氧化铈修饰碳糊电极上的氧化还原反应,结果表明此电极反应为一不可逆的吸附过程。     

线性扫描伏安法测定氟罗沙星

应用线性扫描伏安法和循环伏安法研究氟罗沙星在玻碳电极上的电化学行为。在含有铜离子的pH 6.5的0.10mol.L-1磷酸盐缓冲溶液中,铜离子在玻碳电极上分别于-0.136V和-0.728V处形成两个还原峰,加入氟罗沙星后铜离子的还原峰电位不变但峰电流均降低。在优化的试验条件下,于-0.136V处的峰电流降低值Δip与氟罗沙星浓度在6.40×10-7～1.5×10-4 mol.L-1范围内呈线性关系,检出限为2.10×10-7 mol.L-1。方法用于氟罗沙星片剂中氟罗沙星含量的测定,回收率在96.8%～103.5%之间。     

头孢氨苄在碳糊电极上的电化学行为及其分析研究

用循环伏安法和线性扫描伏安法研究了头孢氨苄在碳糊电极上的电化学行为,考察了不同电解质溶液、pH以及扫描速率等的影响。实验表明:在2.0 mol·L-1HCl支持电解质中,头孢氨苄的降解产物在-0.45 V(vs.SCE)处的电化学还原反应为2电子与2质子参加的受吸附控制的不可逆过程。还原峰电流与头孢氨苄的浓度的平方根在1.8×10-8～3.0×10-4mol·L-1范围内呈良好的线性关系,回收率在95.7%～101.5%范围,检出限(S/N=3)为1.0×10-8mol·L-1。并探讨了头孢氨苄在电极上的反应机理。     

柚皮苷的伏安行为

柚皮苷在pH 8.3的0.05 mol·L-1氯化钾支持电解质溶液中,产生灵敏的线性扫描极谱峰,峰电位为-1.31 V(vs.Ag/AgCl).峰电流与柚皮苷浓度在2.0×10-6～1.5×10-5mol·L-1范围内呈线性关系.用线性扫描和循环伏安法研究体系的伏安行为,结果表明,该电极反应过程为具有吸附性的不可逆过程.     

伏安法测定化妆品中熊果苷

采用线性扫描伏安法、循环伏安法和微分脉冲伏安法等方法研究了熊果苷在玻碳电极上的电化学行为.试验结果表明:pH 2.0的B-R缓冲溶液中,熊果苷在0.86 V(vs.SCE)处有一灵敏的氧化峰,在0 V有一较小的还原峰.以氧化峰为考察对象,对试验条件进行了优化.在最佳条件下,熊果苷浓度在2.0×10-7～4.0×10-6mol·L-1范围内与氧化峰电流呈线性关系,检出限为1.4×10-7mol·L-1.该方法用于膏霜类模拟化妆品中熊果苷的检测,得到的回收率在98.0%～100.6%之间.     

以1-萘胺为底物伏安法测定辣根过氧化物酶

提出了1-萘胺-过氧化氢-辣根过氧化物酶(HRP)伏安酶联免疫分析体系应用于HRP的伏安法测定.在pH 7.0的KH2>PO4-Na2>HPO4缓冲溶液中,HRP催化过氧化氢氧化1-萘胺生成电活性产物,在极谱仪上进行二阶导数伏安线性扫描,该产物在滴汞电极上发生还原反应,于-0.43 V(vs.SCE)左右产生一灵敏的还原峰.HRP浓度在3.0×10-7～5.0×10-5>g·L-1范围内与线性扫描峰电流的二阶导数值(△I"p)呈线性关系,检出限为2.5×10-7g·L-1.     

司帕沙星在单壁碳纳米管修饰电极上的电化学行为及其测定

运用循环伏安法和线性扫描伏安法研究了司帕沙星在单壁碳纳米管修饰电极上的电化学行为,提出了一种简便、准确、灵敏的检测药物司帕沙星的电化学分析方法.在pH 6.0的0.1 mol·L-1Na2HPO4-NaH2PO4缓冲溶液中,司帕沙星在单壁碳纳米管修饰电极上于1.06 V电位处有一峰形很好的氧化峰.在最佳的试验条件下,该氧化峰电流与司帕沙星的浓度分别在1.1×10-6～2.2×10-5mol·L-1和2.7×10-5～1.6×10-4mol·L-1范围内呈线性关系.在开路富集30 s的条件下测得方法的检出限(3S/N)为5.0×10-7mol·L-1.电极上的吸着物质经循环伏安扫描即可除去,从而使电极活性恢复,在SPFX浓度为4.0X10-5mol·L-1的浓度水平下用同一电极连续测定10次,求得相对标准偏差为5.1%,取片剂样品按提出方法分析,测定值与标示值相符.在此基础上用标准加入法作回收试验,测得回收率在97.6%～105.7%之间.     

银盘电极盐酸柔红霉素电化学行为及其与BSA的相互作用

应用线性扫描伏安法和循环伏安法研究盐酸柔红霉素在银盘电极上的电化学行为及其与牛血清白蛋白(BSA)的相互作用.结果表明,在pH6.50的Britton-Robinson缓冲溶液中,盐酸柔红霉素有一灵敏的还原峰,峰电位Ep-0.64V(vs.SCE),缓冲液加入BSA后盐酸柔红霉素的还原峰峰电流下降,据此建立了BSA的电化学测定方法.在优化条件下,峰电流与BSA浓度于1.0×10-8～1.0×10-4mol·L-1(r=0.9965)范围内呈线性关系,检出限为5.0×10-9mol·L-1.同时还测定了盐酸柔红霉素与BSA的结合比和结合常数.     

氨基硅油修饰碳糊电极阳极伏安法测定叶酸

在pH 6.8的B-R缓冲溶液中,采用氨基硅油修饰碳糊电极做工作电极,线性扫描伏安法对叶酸进行测定。伏安图上出现一灵敏的氧化峰,其峰电位EPa=+0.84 V,峰电流与叶酸的浓度在1.6×10-7~6.5×10-6mol.L-1范围内呈线性关系,检出限(3S/N)为7.2×10-8mol.L-1。富集时间为100 s,同时采用循环伏安法研究叶酸在氨基硅油修饰碳糊电极上的氧化还原反应,结果表明此电极反应为一不可逆的吸附过程。     

聚苯基荧光酮修饰玻碳电极吸附溶出伏安法测定痕量汞

研究利用聚苯基荧光酮修饰玻碳电极测定痕量汞的溶出伏安法,在0.1 mol.L-1氨水-NH4Cl缓冲溶液中(pH 9.5),开路搅拌,Hg(Ⅱ)富集于修饰电极表面,通过介质交换至0.1mol.L-1盐酸溶液中,于-0.40 V还原后阳极化线性扫描,在0 V左右处获得一灵敏汞的溶出峰。其氧化峰电流与Hg(Ⅱ)浓度在9.0×10-8~8.0×10-7mol.L-1范围内呈线性关系,开路富集5 min,检出限达2.0×10-8mol.L-1。应用此方法于尿液中汞的测定,所得平均RSD值小于4.02%,回收率试验结果在98.4%~103.2%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%.     

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.     

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.     

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.     

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

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.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.