席夫碱壳聚糖修饰电极的制作及其在对苯二酚测定中的应用

通过共价键合的方法将所制备的席夫碱壳聚糖修饰在玻碳电极表面 ,制成席夫碱壳聚糖修饰电极(SBCME) ,并对其电化学特性进行了研究。利用微分脉冲伏安法测定了对苯二酚 (HQ) ,结果表明 :在 0 .5mol L三羟甲基氨基甲烷 (tris)底液 (pH 3 .0 )中 ,电极对HQ具有良好的吸附性与选择性 ,HQ浓度在 1 .0× 1 0 - 6～ 2 .0×1 0 - 3mol L范围内与其氧化峰电流呈线性关系 ,检出限可达 1 .0× 1 0 - 7mol L。利用此电极测定样品 ,结果满意     

流动注射化学发光抑制法测定痕量抗坏血酸

研究发现在碱性介质下，抗坏血酸对 Luminol-K3Fe（CN）6体系发光反应具有强烈的抑制作用，建立了化学发光抑制快速测定痕量抗坏血酸的新方法。本法测定抗坏血酸的线性范围为4．0×10－8～1．0×10-6mol／L，D．L＝40×10－8mol／L，对1．0×10－7mol／L抗坏血酸连续11次测定的相对标准偏差为0．5％，应用于医用维生素C片剂、维生素针剂以及血样中抗坏血酸的测定，结果满意。     

壳聚糖修饰玻碳电极卷积伏安法测定环境水中的EDTA

制备了壳聚糖修饰玻碳电极 ,研究了Fe(EDTA) -在修饰电极上的吸附还原行为 ,用卷积伏安法通过Fe(EDTA) -的检测测定了环境水中的EDTA。在优化的实验条件下 ,峰电流值与 8.0× 1 0 -7～ 5 .0× 1 0 -6mol L的EDTA呈线性关系 ,回归方程为epp′ =0 .75 2 5c - 0 .661 3,r =0 .991 ,最低检出限为 5 .0× 1 0 -7mol L ,5次测定的相对标准偏差小于 5 .8%。对实际样品测定的回收率为98 1 %～ 1 0 5 % ,对比HPLC的结果 ,相对偏差小于 5 %。     

碳纳米管修饰电极对多巴胺和抗坏血酸的电催化氧化

研究了碳纳米管修饰玻碳电极 (NTCME)的制备方法及对多巴胺 (DA)和抗坏血酸 (AA)的电催化氧化作用。在磷酸盐缓冲溶液 (PBSpH 7.4)中 ,以NTCME为工作电极时 ,DA与AA的氧化电位分别为 0 .2 6和 0 .0 1V(vs.SCE) ,比在裸玻碳电极 (GC)上分别降低了 0 .0 7和 0 .6 2V。NTCME能消除DA与AA共存时测定的相互干扰。利用二阶导数卷积伏安法测定 ,DA与AA分别在 2 .0 0× 10 - 6～ 3.84× 10 - 4 和 7.99× 10 - 5～ 3.6 6× 10 - 3 mol L浓度范围内 ,峰高与浓度呈线性关系 ;检出限分别为 1.90× 10 - 7和 5 .96× 10 - 5mol L。     

毛细管电泳-电化学检测测定茶叶中咖啡因、表儿茶素和抗坏血酸

高效毛细管电泳电化学检测同时测定了6种茶叶中的咖啡因、表儿茶素和抗坏血酸的含量,考察了实验参数对分离、检测的影响。在最佳实验条件下,以300 靘直径的碳圆盘电极为检测电极,检测电极为1.20 V(vs.SCE),在25 mmol/L硼酸盐25 mmol/L磷酸盐(pH 7.6)的混合运行缓冲液中,上述各组分在16 min内能完全分离。咖啡因、表儿茶素和抗坏血酸在2×10-3mol/L～１×10-5 mol/L、5×10-5mol/L～5×10-7mol/L、2×10-4 mol/L～1×10-5mol/L范围内呈线性关系,检测下限分别为6×10-6mol/L、4×10-7mol/L和1×10-6mol/L。该法直接用于茶叶中咖啡因、表儿茶素和抗坏血酸的测定,结果令人满意。     

基于尼古丁对胆碱氧化酶的抑制作用测定尼古丁的研究

基于尼古丁对胆碱氧化酶(CHOD)的抑制作用,将胆碱氧化酶电极用于微量尼古丁的测定。酶电极制作中,先在铂电极表面修饰一层壳聚糖膜,再用戊二醛交联CHOD。采用这种酶固定化方法,电极在4. 0×10-6 ~ 3×10-3 mol/L胆碱的浓度范围呈线性关系。探讨了工作电位、pH、底物浓度等实验条件对酶电极性能及抑制过程中响应电流的影响,测定了电极的重现性、干扰及使用寿命。电极检测尼古丁的线性范围为1. 5×10-5 ~3×10-3 mol/L;检出限为1. 25×10-5 mol/L。将电极用于实际样品烟草中尼古丁回收率的测定,结果良好。     

L-半胱氨酸自组装膜修饰金电极对抗坏血酸的电催化作用及其测定

金电极表面对L 半胱氨酸 (L Cys)有特性吸附 ,而L Cys分子在等电点pH附近因静电引力和氢键作用形成分子对 ,从而在电极表面自组装形成L Cys双层膜。L Cys修饰金电极对抗坏血酸 (AA)具有良好的电催化作用。用示差脉冲伏安法对AA进行了测定 ,氧化电流与AA的浓度在 1.0× 10 -3 ～ 4× 10 -6mol/L范围内呈良好的线性关系 ,线性相关系数为 0 .9981;检出限为 4× 10 -7mol/L。用于药片中AA含量的测定 ,结果令人满意。     

流动注射化学发光增强法测定健民咽喉片中的没食子酸

在pH 9.4的Na2 CO3 NaHCO3介质中 ,没食子酸对鲁米诺 K3Fe(CN) 6 发光体系有很强的增敏作用。据此建立了流动注射化学发光增强法测定没食子酸的方法。发光信号的增强值 (ΔI)与没食子酸的浓度在1 0× 1 0 - 6 ～ 8.0× 1 0 - 9mol L的范围内呈良好的线性关系 ,检出限为 5 .6× 1 0 - 9mol L。对于 1 .0× 1 0 - 7mol L的没食子酸测定 ,相对标准偏差为 2 .2 % (n =1 1 )。该法可用于健民咽喉片中没食子酸含量的测定     

基于壳聚糖-纳米金/纳米普鲁士蓝/L-半胱氨酸修饰的 葡萄糖传感器的研究

在金电极表面修饰一层L-半胱氨酸,再利用静电吸附作用固定纳米普鲁士蓝(nano-PB),然后利用壳聚糖-纳米金复合膜将葡萄糖氧化酶(GOD)固定于修饰电极表面,制成新型的葡萄糖传感器.通过交流阻抗技术,循环伏安法和计时电流法考察了电极的电化学特性.在优化的实验条件下,该传感器在葡萄糖浓度为3.0×10-6～1.0×10-3 mol/L范围内有线性响应,检测下限为1.6×10-6 mol/L.此外该传感器具有响应快、稳定性好和选择性良好的特点,能有效排除常见干扰物质如抗坏血酸、尿酸等对测定的影响.     

纳米金修饰玻碳电极在抗坏血酸共存下选择性测定多巴胺

利用电沉积的方式制备了纳米金 ( Nano- gold,NG)修饰玻碳电极 ( GCE)。该电极对多巴胺 ( DA)和抗坏血酸 ( AA)均有催化作用 ,且多巴胺在纳米金修饰玻碳电极上有较强的吸附作用。同时研究了磷酸缓冲溶液的 p H值和离子强度对 DA的电化学行为的影响。纳米金修饰玻碳电极在 DA和 AA的混合溶液中的循环伏安图上可观察到两个明显分开的氧化峰 ,峰电位差达到 1 5 0 m V。据此 ,提出了两种利用该电极在抗坏血酸共存下选择性测定多巴胺的方法 ,线性范围分别为 3.0× 1 0 - 6 ～1 .0× 1 0 - 4mol/ L和 1 .2 5× 1 0 - 6 ～ 1 .0× 1 0 - 4mol/ L。     

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%).