流动注射安培法快速测定食盐中碘

报道了在酸性溶液中 ,IO- 3可被过量的I- 还原 ,FI流动注射安培法快速测定食盐中碘的方法。溶解于蒸馏水中的食盐样品 (30 μl)注入pH 1的 0 .1mol·L- 1NaCl + 1× 10 - 3mol·L- 1KI的载液中。自行研制的壁喷玻碳电极安培流通检测池作为工作电极 ,电位为 + 0 .2V(vs.SCE)。该系统和反向 (注入KI)系统的线性范围均为 1× 10 - 6 ～ 1× 10 - 4mol·L- 1,检出限为 5× 10 - 7mol·L- 1,相对标准偏差为 0 .8% (n =37) ,样品测定的回收率为 97.6 %～ 10 4 % ,采样频率 90样·h- 1。通过Bernoull恒流瓶可获得无脉冲载流。     

普鲁士兰修饰碳黑微电极同时微分伏安法测定多巴胺和抗坏血酸

将含有1.0%普鲁士蓝的碳黑与固体石蜡按2.5∶1(质量比)混合后装入φ0.2mm的石英毛细管中,在其上端插入一铂丝并抛光后即制成普鲁士蓝修饰碳黑微电极.对多巴胺(DA)及抗坏血酸(VC)在此电极上的电化学行为及应用此电极测定两组分的最佳条件进行了研究,在定量测定中采用二次微分线性扫描伏安法.在最佳条件下,DA与VC的峰电流(i″p)分别与各自的浓度保持如下线性关系DA为4.0×10-6～8.0×10-4mol·L-1,VC为6.0×10-5～1.0×10-3mol·L-1;检出限(3σ)依次为2.0×10-6mol·L-1及1.0×10-5mol·L-1.应用此方法分析了3种含DA及VC的混合溶液,测得结果的相对标准偏差(n=8)依次小于2.0%及3.0%,回收率范围依次为96.5%～101.0%及95.0%～102.5%.     

电位溶出分析法同时测定罐头食品中痕量铅锡

利用不除氧电位溶出分析法成功地测定了溶出电位相近的铅、锡两元素。以0.05mol·L-1草酸为介质,调节溶液pH1.0,以溶解氧作氧化剂,静止溶出,两元素均有分离清晰的平台出现。铅、锡的线性范围分别为2.0×10-9～2.0×10-7mol·L-1和2.0×10-8～2.0×10-6mol·L-1。当富集时间为4min时,铅、锡的检出限分别为5.0×10-10mol·L-1和5.0×10-9mol·L-1。此法已成功地应用于测定罐头食品中痕量铅和锡。     

Nafion-1,10-二氮杂菲修饰玻碳电极及其在钌的伏安分析中的应用

制备了Nafion 1,10 二氮杂菲修饰电极 ,研究了钌在此修饰电极表面的伏安特性。用微分脉冲伏安法测定钌 ,钌的浓度在 1× 10 - 6 ～ 1× 10 - 9mol·L- 1范围内 ,电流与浓度呈线性关系 ,其检出限为 5 .14× 10 - 9mol·L- 1。     

L-半胱氨酸自组装膜修饰电极对对氨基酚电催化氧化及其分析应用

在裸金电极上制备了L 半胱氨酸自组装膜修饰电极(L Cys/AuSAMs),研究了对氨基酚(p AP)在L Cys/AuSAMs上的电化学行为,发现该膜电极对p AP的氧化具有良好的电催化作用。氧化峰电位降低了128mV,测得p AP的扩散系数D为1.27×10-6cm2·s-1,初步探讨了电催化机理。采用水平衰减全反射 傅立叶变换红外光谱(ATR FTIR)技术对L Cys/AuSAMs进行了表征;方波伏安法(SquareWaveVoltammetry,SWV)测定p AP,其氧化峰峰电流与p AP浓度在1.0×10-8～8.0×10-8mol·L-1和1.0×10-7～2.0×10-4mol·L-1范围内呈线性关系,相关系数分别为0.9978和0.9977,检出限为2.0×10-9mol·L-1。该电极用于模拟废水样的测定,结果满意。     

2-羟基-3-(三乙胺基)丙基十烷基硫醚修饰电极测定痕量金

研究了 2 羟基 3 (三乙胺基 )丙基十烷基硫醚 (HTPSD)修饰玻碳电极测定金的伏安特性及分析条件。在 0 .2mol·L- 1KCl HCl缓冲溶液中 (pH 1) ,金 (Ⅲ )被富集到电极表面 ,然后介质交换到 0 .2mol·L- 1KCl HCl空白溶液中 (pH 1)进行阴极溶出伏安测定 ,金 (Ⅲ )浓度在 2× 10 - 81× 10 - 6mol·L- 1范围内呈线性关系。检出限为 1× 10 - 8mol·L- 1。相对标准偏差小于 6 2 % ,一般常见离子不干扰。     

抗坏血酸在聚甲苯胺蓝膜修饰的玻碳电极上的电催化氧化及流动注射分析

在玻碳电极上用循环伏安法电聚合一层聚甲苯胺蓝膜,该膜修饰电极对抗坏血酸(VC)的氧化具有良好的电催化作用,能够降低其过电位约100mV。将该修饰电极应用于流动注射能大大提高VC的检测灵敏度,其线性范围为2.0×10-7～1.2×10-3mol·L-1,检出限为4.8×10-8mol·L-1,连续注射检测,其电流信号能够保持稳定24h。     

流动注射双安培法测定没食子酸

基于没食子酸在经预阳极化的铂电极上的催化氧化和不可逆电对的双安培检测原理,使用经过恒电位预阳极化处理的双铂电极,在外加电位差为0V时,通过偶合没食子酸在一支电极上的氧化和氧化铂在另一支电极上的还原两个不可逆电极过程,构建流动注射双安培检测体系,建立了一种流动注射双安培直接检测没食子酸的新方法。常用药物赋形剂、无机离子以及生化样品中一些共存物均不干扰没食子酸测定。没食子酸的氧化电流与其浓度在1.0×10-5～1.0×10-3mol/L范围内有良好的线性关系。检出限为5.0×10-6mol/L。连续20次测定2.0×10-4mol/L没食子酸,电流值的RSD为1.7%。该方法有很高的选择性和灵敏度,样品处理方法简单快速,适于在线分析。     

在二甲亚砜中La—Fe合金膜电化学制备的研究

研究了二甲亚砜 (DMSO)中La3 和Fe2 在Pt ,Cu和Ni电极上的电化学行为。Fe2 在Pt电极上一步不可逆还原为Fe ,La3 在Pt电极上表现为准可逆电极过程。在 2 98K时 ,利用循环伏安法测定了 0 0 1mol·L- 1 FeCl2 0 1mol·L- 1 LiCl DMSO溶液中Fe2 的扩散系数、传递系数分别为 2 5 4× 10 - 6 cm2 ·s- 1 和 0 2 4;利用计时电流法测定了 0 0 1mol·L- 1 LaCl3 0 1mol·L- 1 LiCl DMSO溶液中La3 的扩散系数为 3 10×10 - 6 cm2 ·s- 1 。在铜电极上于 -1 75 0～ -2 45 0V (vs .SCE)下恒电位电解 ,可获得La含量达 2 2 7%～ 3 7 1%的La Fe合金膜 ;应用脉冲电解技术于 2～ 6mA·cm- 2 也可获得La Fe合金膜。这些合金膜是均匀的 ,粘附性好并有金属光泽     

铟(Ⅲ)-二溴邻苯二胺双草酰胺酸酯配合物电化学行为研究及应用

在0.05mol·L-1氯乙酸 氯乙酸钠(pH3.0)介质中,In(Ⅲ)与二溴邻苯二胺双草酰胺酸酯(DBPMACE)生成配合物,并吸附于电极表面,于-0.63V(vs.SCE)得到配合物吸附还原波。其二次微分极谱峰电流与In(Ⅲ)浓度在7.5×10-8～3.4×10-6mol·L-1内呈良好的线性关系,检出限为1.5×10-8mol·L-1。应用于陶瓷颜料、矿石中微量铟的测定,结果满意。并对电化学反应机理进行了初步探讨。     

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.