多壁碳纳米管修饰电极同时测定维生素B2、B6、B12和维生素C

制备了多壁碳纳米管修饰玻碳电极(MWNT/GCE),研究了维生素B2、B6、B12和维生素C共存时在该电极上的电化学行为.实验发现,在HAc-NaAc缓冲溶液中,该电极可同时测定以上四种维生素,线性范围分别为1.0×10-6～1.0×10-4 mol/L、5.0×10-5～2.0×10-3 mol/L、5.0×10-5～7.5×10-4 mol/L和5.0×10-5～2.0×10-3 mol/L,其检出限分别为7.0×10-7 mol/L、1.0×10-5 mol/L、2.5×10-5 mol/L和5.0×10-6 mol/L.样品分析的RSD分别为1.66%、1.71%、2.26%和1.46%.方法简便快捷,可用于四种维生素同时分析测定.     

敌百虫催化联苯胺-过硼酸钠体系的极谱行为及其应用

用单扫描极谱方法研究发现敌百虫催化联苯胺过硼酸钠体系产生一灵敏的还原峰,其峰电位为-0.7V(vs.SCE),峰电流与敌百虫的浓度在8×10-7～1×10-4mol/L范围内呈良好的线性关系(r=09991),据此提出了一种检测敌百虫的新方法。检出限为8×10-8mol/L。对8×10-5mol/L的敌百虫溶液进行6次平行实验,RSD为3.06%。研究了电极反应机理,并应用本方法测定植物样品中敌百虫的残留量,结果良好。     

时间驱动荧光猝灭法测定痕量Cu(Ⅱ)

研究了Cu-酪氨酸荧光静态猝灭体系,络合物为Cu(Tyr)22 ,猝灭常数K为1.59×1010.以时间驱动模式代替浓度模式,在pH 8.8的硼砂介质中,测得Cu2 的线性范围为4.00×10-7～1.12×10-5 mol/L和8.00×10-6～1.12×10-4 mol/L,相关系数R=0.9996/0.9992,检出限(3σ)为6.6 × 10-8 mol/L,相对标准偏差(RSD)为0.78%(n=11,C(Cu2 )=2.4×10-6 mol/L).本方法可用于实际样品中痕量铜的测定.     

吡啶类碳离子液体电极对酚磺乙胺的电化学行为及其分析应用

用离子液体1-丁基吡啶六氟磷酸盐(BuPyPF6)作为粘合剂构置了碳离子液体修饰电极(BuPyPF6-CILE).在0.05 mol/L H2SO4溶液中,用循环伏安法研究了在BuPyPF6-CILE和传统碳糊电极(TCPE)上酚磺乙胺(ESL)的电化学行为,建立了测定尿样和血清样品中ESL含量的新方法.ESL在BuPyPF6-CILE上的氧化峰电流响应是其在TCPE上的8.7倍,峰电位差降低到0.101 V,电子转移速率常数Ks=0.544 s-1,电极表面平均吸附量为1.66×10-9 mol·cm2.ESL的氧化电流与其浓度在8.0×10-8～2.0×10-6mol/L和5.0×10-6～1.0×10-4mol/L范围内呈线性关系,检出限为3×10-8mol/L(S/N=3).连续5次测定2.0×10-6mol/L ESL溶液的RSD为1.5%.     

三重比光谱导数法同时测定氨基酸注射液中的三种芳香氨基酸

采用三重-比光谱导数分光光度法同时测定氨基酸注射液中的3种芳香氨基酸,讨论了测定酪氨酸、苯丙氨酸和色氨酸的实验条件.实验结果表明,在pH 7.4的NaH2PO4-NaOH缓冲溶液中,3种氨基酸的线性范围分别为:酪氨酸2.0×10-6～2.8×10-5 mol/L,苯丙氨酸2.0×10-5 ～1.6×10-3 mol/L,色氨酸4.0×10-7～1.6×10-6 mol/L.回收率在95%～105%之间.     

流动注射化学发光法测定3种氟喹诺酮类药物

研究发现,氟喹诺酮类药物对可溶性Mn(-甲醛化学发光体系有强烈的增敏作用,结合流动注射技术,建立了3种氟喹诺酮类药物诺氟沙星、氧氟沙星和环丙沙星的流动注射化学发光新方法。在优化的实验条件下(2×10-4molMn(-3%甲醛-3mol/L磷酸),本方法测定诺氟沙星、氧氟沙星和环丙沙星的线性范围分别为1.0×10-7～1.0×10-5mol/L,1.0×10-7～1.0×10-5mol/L和3.0×10-7～5.0×10-5mol/L;检出限分别为3×10-8mol/L,3×10-8mol/L,1×10-7mol/L;相对标准偏差(5.0×10-6mol/L氟喹诺酮类药物,n=11)分别为2.6%,1.6%和2.8%。该方法已用于诺氟沙星胶囊中诺氟沙星的含量测定。     

微型毛细管电泳安培检测无糖口香糖中的木糖醇和山梨醇

采用微型的毛细管电泳-安培(CE-AD)测定装置对市售的3种无糖口香糖中的木糖醇和山梨醇的测定进行了研究。实验采用铜盘工作电极,在0.65V的检测电位下,用70mmol/L NaOH缓冲溶液,4kV的分离电压,木糖醇和山梨醇在10min之内实现了良好的分离,其中木糖醇的线性范围为5×10-5~1×10-2mol/L,山梨醇的线性范围为5×10-5~5×10-2mol/L(r>0.9997),检出限分别为5×10-6mol/L和2.5×10-6mol/L。该方法测定样品中木糖醇和山梨醇的相对标准偏差和回收率分别为3.7%、4.5%和98.1%、91.1%(n=10)。将该方法用于好丽友口香糖、益达口香糖、华艾康口香糖中木糖醇和山梨醇的测定,结果令人满意。     

联吡啶钌体系电化学发光法测定克林霉素的研究

建立了以金电极为工作电极电致化学发光测定盐酸克林霉素的方法,并采用循环伏安和电致化学发光法,研究了体系的电化学行为和电化学发光行为.研究结果表明,在0.1 mol/L的硼酸(pH 8.0)缓冲溶液中,扫描速率为100 mV/s时,ECL的峰高与盐酸克林霉素浓度在1.0×10-5 ～1.0×10-4 mol/L和1.0×10-7 ～8.0×10-6 mol/L范围内呈线性关系,其线性回归方程分别为I(counts)=465.00×105c-133.80(r=0.996 8)和I(counts)=20.333×106c+100.25(r=0.995 9).方法的检出限为1.0×10-7 mol/L(S/N=3).连续测定2.0×10-5 mol/L的盐酸克林霉素溶液10次,发光强度值的RSD为1.74%.对样品进行加标回收率实验,回收率为93% ～102%.该方法具有较高的选择性和灵敏度,样品处理简单快速,用于盐酸克林霉素胶囊的测定,结果满意.     

氧化石墨烯/铁氰化铈修饰玻碳电极同时测定扑热息痛和咖啡因

采用滴涂法和电沉积法制备了氧化石墨烯/铁氰化铈(CeFe(CN)6)纳米复合膜修饰玻碳电极。用扫描电镜对氧化石墨烯和氧化石墨烯/CeFe(CN)6纳米复合膜进行了表征。分别用循环伏安法和差分脉冲伏安法研究了扑热息痛和咖啡因在修饰电极上的电化学行为。结果表明,在0.1 mol/L醋酸盐缓冲溶液(pH5.0)中,扑热息痛和咖啡因在此修饰电极上具有良好的电化学行为,扑热息痛和咖啡因分别在1.0×10-7～6.0×10-5mol/L和1.0×10-6～1.3×10-4mol/L浓度范围内与电化学响应信号呈良好的线性关系,相关系数分别为0.990和0.992;信噪比为3时,扑热息痛和咖啡因检出限分别为5.0×10-8mol/L和5.2×10-7mol/L。将本方法用于人尿样品分析,回收率为96.1%～105.4%。     

差分脉冲溶出伏安法测定陶瓷器皿中铅和镉的溶出率

采用4%的乙酸浸泡陶瓷样品24 h,应用同位镀汞差分脉冲溶出伏安法测定了陶瓷样品中微量重金属铅、镉的溶出量。以0.1 mol/L的硝酸溶液做底液,0.1 mol/L的KCl溶液做支持电解质,2 g/L的Hg2+溶液做镀汞液,测得铅的溶出峰电位为-0.5 V(vsSCE),镉的溶出峰电位为-0.7 V(vsSCE),两者含量在5×10-4～1 mg/L和5×10-4～0.5 mg/L范围内峰电流和其含量呈良好的线性关系,检出限分别为2×10-4和4.3×10-3mg/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%.     

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.