锰C-抗坏血酸甲醛-化学发光体系的研究

实验观察到锰 氧化抗坏血酸可以产生弱的化学发光 ,甲醛对这一化学发光反应有较强的增敏作用 ,据此建立了测定抗坏血酸的流动注射化学发光分析法。方法的检出限为 2× 1 0 -8mol/L抗坏血酸 ;线性响应范围为 6 .0× 1 0 -8～ 2 .0× 1 0 -5mol/L。对 1 .0× 1 0 -6mol/L的抗坏血酸进行 1 1次测定 ,相对标准偏差为 2 3%。该方法已成功应用于维生素C针剂和片剂中抗坏血酸含量的测定 ,结果与药典方法测得值一致     

全固态铅离子选择性电极测定人发中微量铅

提出了用全固态铅离子选择性电极测定人发中微量铅的方法。在 1.5 g·L- 1抗坏血酸 1g·L- 1三乙烯四胺 0 .0 5mol·L- 1高氯酸钠 ,pH 4.85 .5的条件下 ,采用格氏作图法可准确测定人发中微量铅。方法简便、准确度高 ,回收率 95 % 10 6% ,相对标准偏差小于 5 .3 %。     

动力学荧光法测定抗坏血酸

基于在硫酸介质中 ,抗坏血酸能活化钒 ( )催化溴酸钾氧化藏红 T的反应 ,使其荧光猝灭 ,建立了动力学荧光法测定抗坏血酸的新方法。方法的检出限为 5 .8× 1 0 -3 μg/m L,线性范围为 0～ 0 .5 6μg/m L。可用于药品、蔬菜、尿液中抗坏血酸含量的测定     

利用扫描电化学显微镜研究过氧化氢检测中电化学消除抗坏血酸

利用扫描电化学显微镜 (SECM)将微探针定位于宏观金盘基底电极的扩散层内 .通过向基底电极施加适当电位以氧化消除电活性干扰物质 (如抗坏血酸 ) ,提高探针电极检测过氧化氢的选择性 .基于此方法 ,系统研究了探针 -金基底电极间距和电极电位对铂微探针检测过氧化氢选择性的影响 .结果表明 ,当探针 -基底电极间距为 2 2 .6μm ,金基底电极和铂探针电极电位分别为 0 4V和 0 5V时 ,探针电极检测过氧化氢不受抗坏血酸 ( 0 0 5mmol·L-1)的干扰 .此时 ,过氧化氢检测的线性范围为 :4× 10 -5～ 1× 10 -3 mol·L-1.基于实验结果 ,提出了在微型化电化学器件制备过程中设计互相靠近的双工作电极 ,利用电化学法消除电活性干扰物以提高检测选择性的新方法 .     

考马斯亮蓝G光度法测定钼的研究

考马斯亮蓝Ｇ是一种生物染色剂 ,在分析测定中多用于蛋白质的测定[1 ,2 ] 。近年也有人用此试剂做催化动力学分析中的指示剂[3 ,4] 。我们在研究中发现 ,考马斯亮蓝Ｇ用于缔合物体系测定阳离子 ,有较好的结果。本文研究了以铜离子为催化剂 ,在抗坏血酸存在下的钼 硫氰酸盐 考马斯亮蓝显色体系 ,建立了一个灵敏的测定钼的方法。该方法灵敏度高 ,其表观摩尔吸光系数ε50 0 =2 .3 1×1 0 5Ｌ·ｍｏｌ- 1 ·ｃｍ- 1 。线性范围宽 ,钼的浓度在 0～2 1 μｇ/2 5ｍＬ范围内符合比尔定律。选择性较高 ,显色时间短 ,适合于生产中使用。该方法可用于合…     

壳聚糖修饰电极上的铁氰根离子对抗坏血酸的电催化氧化作用

在玻碳电极表面滴涂一层壳聚糖膜 ,壳聚糖分子中 -NH2 在酸性溶液中发生质子化 ,靠静电引力作用吸附富集荷负电的电子介体Fe(CN) 63 -,使其固定在电极表面 ,研究了此Fe(CN) 63 - 壳聚糖 GC修饰电极对抗坏血酸的催化氧化作用。抗坏血酸的浓度在 3.0× 1 0 -6～ 5 .0× 1 0 -3 mol L范围内呈很好的线性关系 ,相关系数为 0 .998,检测限达 1 .0× 1 0 -6mol L。该法已用于测定蔬菜中抗坏血酸的含量。     

固蓝盐B分光光度法测定药物中抗坏血酸

探讨了一种简便的选择性高的药物中抗坏血酸的测定方法。该方法是基于在酸性介质中抗坏血酸和固蓝盐B的反应,产物的最大吸收为420nm.摩尔吸光系数为1.31×10~4L·mol~(-1)·cm~(-1).方法已应用于某些药物中抗坏血酸的测定,结果与碘量法一致,回收率为98.4％～105％,相对标准偏差低于3.7％。     

二安替比林对甲基苯基甲烷与Ce（Ⅳ）的显色反应研究

研究了二安替比林对甲基苯基甲烷 (DAp MM)与 Ce( )的显色反应 ,在 H3PO4 介质中 ,DAp MM与 Ce( )生成橙色产物。λmax=485nm,ε=3.53× 1 0 5L·mol-1·cm-1。Ce( )含量在0 .5～ 8.0μg/2 5ml内符合比耳定律 ,该体系灵敏度高 ,选择性好 ,用于镁合金和含锌矿石中微量铈的测定 ,结果满意。     

偶氮氯膦—DBC光度法测定银合金中镨

研究提出镨 ( ) - DBC-偶氮氯膦 -磷酸 - EDTA新体系光度法测定贵金属合金中微量镨。反应体系生成 α型蓝色配合物的 λmax=650 nm,灵敏度高 ,摩尔吸光系数 ε=0 .93× 1 0 5L·mol-1·cm-1,镨浓度在 0～ 50 μg/2 5ml范围内符合比耳定律 ,方法选择性强 ,有较好的适用性 ,用于分析银合金中镨 ,标准偏差 S≤ 0 .0 1 1 ,相对标准偏差 RSD≤ 1 .97%。     

新显色剂三甲氧基苯基荧光酮光度法测定锗

研究了新试剂三甲氧基苯基荧光酮光度测定锗的方法。在 3mol/ m LH3PO4 介质中 ,当 Triton X- 1 0 0存在时 ,锗与三甲氧基苯基荧光酮形成 1∶ 2橘红色络合物 ,最大吸收在 5 0 5 nm波长处 ,摩尔吸光系数为 1 .7× 1 0 5L· mol-1·cm-1且具有高的选择性。当锗含量在 0～ 6μg/ 2 5 m L范围内符合比尔定律。已用于大蒜与枸杞子中锗的测定     

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%.     

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.     

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%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

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.