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。     

铜-鲁米诺化学发光法测定抗坏血酸

本文采用鲁米诺-铜-抗坏血酸体系,建立了一种化学发光测定抗坏血酸的方法,方法具有操作简单,灵敏度高,重复性好等优点,用该方法测定抗坏血酸的线性范围为2.0×10~(-6)～6.0×10~(-5)mol/L,对4.0×10~(-6)mol/L抗坏血酸连续11次测定的相对标准偏差(RSD)为1.1％,用建立的方法对市售饮料、复合维生素及维生素片剂中的抗坏血酸进行了测定,结果满意.     

Nafion-甲基紫精修饰电极抗坏血酸氧化酶生物传感器的研究

本文用Nafion-甲基紫精修饰电极为基底,以牛血清白蛋白和戊二醛为交联剂,将抗坏血酸氧化酶固定在电极上,制成修饰电极抗坏血酸氧化酶生物传感器。用这种生物传感器测定人体血清中抗坏血酸,线性范围在7.5×10~(-4)～7.5×10~(-7)mol/L之间,响应时间为5s,检测下限为2.5×10~(-7)mol/L。该传感器具有选择性好、灵敏度高和响应时间短等特点。     

生姜组织膜L—抗坏血酸传感器的制备及药片测定中应用

用生姜组织同氧电极配合,制成植物组织膜L-抗坏血酸传感器。在4.0×10~(5-)～1.1×10~(-3)mol/L浓度范围内,响应信号与L-抗坏血酸呈线性关系。电极寿命至少30天。用于药片中L-抗坏血酸含量测定。结果与药典法和极谱法相符。     

伏安型植物组织生物微电极的研究——茄子组织碳糊微电极的研究

茄子组织生物微电极在儿茶酚测定中表现出了较高的生物催化活性,而对抗坏血酸测定则为稳态响应,这表明该电极能有效地消除抗坏血酸的干扰。该电极的灵敏度高,重现性好,对多巴胺测定的线性范围为5.8×10~(-6)～6.5×10~(-4)mol/L,检出下限为:2.9×10~(-6)mol/L。     

三维荧光光谱法连续测定苯胺、二苯胺和N-甲基苯胺

本文比较了苯胺、二苯胺、N-甲基苯胺的二维荧光光谱和三维荧光光谱。提出了同时测定苯胺,二苯胺和N甲基苯胺的分析方法,它们的浓度分别在2.0×10~(-7)～5.0×10~(-6)mol/L,9.0×10~(-8)～7.4×10~(-6)mol/L,1.3×10~(-7)～2.0×10~(-8)mol/L范围内有良好的线性关系,检出限为1.0×10~(-7)mol/L,8.0×10~(-9)mol/L,1.0×10~(-7)mol/L.相对标准偏差分别为5％,7％,7％.此方法用于混合样品和工业废水的分析,获得较满意的结果.     

导数示波极谱法测定大气和水中痕量硫化物

本文提出以导数示波极谱法直接测定各种水质和大气中痕量硫化物,底液为0.032mol/LEDTA—0.10mol/L NaOH—0.040mol/L抗坏血酸。在—0.70V(V_·SCE)处,获得一灵敏的导数峰电流。硫化物浓度在9.38×10~(-9)～5.16×10~(-4)mol/L之间与峰电流有线性关系。检测限为3.12×10~(-9)mol/L。用本方法分别测定大气中的H_2S和水中的硫化物,获得满意结果。     

青椒籽浆-碳糊生物电极的研制及应用

本文研制了青椒籽浆-碳糊生物电极,并探讨了电极的性能及实用性,实验表明,该电极可用于伏安法快速检测L-抗坏血酸,线性范围为1.15×10~(-5)～1.24×10~(-4)mol/L,检测下限可达到9.87×10~(-6)mol/L,电极具有良好的重现性和选择性,响应时间短,使用寿命为12d。     

铬(Ⅵ)-过氧化氢-鲁米诺化学发光法测定痕量抗坏血酸

基于抗坏血酸与铬(Ⅵ)的还原反应产生的铬(Ⅲ)催化鲁米诺-过氧化氢发光体系的研究, 建立了一种快速测定痕量抗坏血酸的新方法.该方法线性范围为8.0×10-9～1.6×10-4 mol/L,检出限为8.0×10-9 mol/L,对1.0×10-6 mol/L抗坏血酸11次平行测定的RSD为0.9%.用于医用维生素C片剂中抗坏血酸含量的测定, 结果令人满意.     

氨基萘磺酸盐无保护流体室温燐光的取代基位置效应

以TINO_3作重原子微扰剂,Na_2SO_3作化学除氧剂,在无需加入任何保护介质条件下,仅需仪器光源适当照射,1-氨基4-萘磺酸盐、1-氨基5-萘磺酸盐、2-氨基1-萘磺酸盐水溶液均能产生强而稳定的室温燐光信号(RTP)。3种氨基萘磺酸盐浓度分别在4.0×10~(-8)～1.2×10~(-5)mol/L;1.2×10~(-6)～1.6×10~(-5)mol/L;1.6×10~(-7)～8.0×10~(-6)和8.0×10~(-6)～2.5×10~(-5)mol/L范围内与RTP信号呈良好线性关系。检出限分别为3.8×10~(-9_、1.4×10~(-7)和2.8×10~(-8) mol/L。1-氨基 7-萘磺酸盐和1-氨基 8-萘磺酸盐在相同条件下则不能产生RIP信号,表明取代基位置对RTP发射有重要影响。     

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%.     

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.     

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.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.