催化电位滴定法测定奶粉中微量锌

报道了一种以氨三乙酸(NTA,活化剂)存在下锰(Ⅱ)催化KIO4氧化甲基紫的反应指示滴定终点,自制的甲基紫选择性电极为指示电极,用催化电位滴定法测定奶粉中微量锌的新方法。将该方法用于奶粉中锌的测定,结果与火焰原子吸收光谱法一致,样品平均回收率为99．0％,RSD为1．1％。     

用电活性离子对制成的离子选择电极测定阳离子表面活性剂

制备了3种基于不同电活性物质(十二烷基二甲基苄基铵-四苯硼、十六烷基三甲基铵-四苯硼、十八烷基三甲基铵-四苯硼)的阳离子表面活性剂离子选择电极,并对其性能做了测定,结果显示该类电极对阳离子表面活性剂十二烷基二甲基苄基氯化铵、十六烷基三甲基溴化铵、十八烷基三甲基氯化铵均有能斯特响应。以此类电极作为指示电极,四苯硼钠溶液作为滴定剂,对阳离子表面活性剂(十二烷基二甲基苄基氯化铵、十八烷基三甲基氯化铵、海明1622)进行了活性物含量的测定,与两相滴定法测定结果进行了比较。     

用氯离子电极同时测定阳离子表面活性剂的CMC及反离子缔合度

临界胶束浓度(CMC)是研究表面活性剂的一个重要参数,胶束的反离子缔合度(K)是重要的特性参数。本文以阳离子表面活性剂十烷基三甲基氯化铵(DTMAC)、十二烷基三甲基氯化铵(DTAC)、十四烷基三甲基氯化铵(TTAC)、十六烷基三甲基氯化铵(CTAC)和十八烷基三甲基氯化铵(OTAC)水溶液体系为研究对象,用氯离子选择电极分别测定了其水溶液体系胶束的CMC和K。     

酸性铬蓝K和次甲基蓝的库仑滴定

酸性铬蓝K可用还原剂Cr~(2+)、Ti~(3+)测定,但还原过程较慢,在高温下才完全反应。Rukmini等人提出在常温下以草酸为催化剂,用TiCl_3滴定次甲基蓝。本文提出在室温下,以Mn~(2+)为催化剂,在0.2M柠檬酸钠-0.6M三乙醇胺-0.001M Mn~(2+)-0.1M TiCl_4酸性溶液中(pH2～3)用电生Ti~(3+)库仑滴定酸性铬蓝K和次甲基蓝。Ag-Hg电极为工作电极,铂电极为辅助电极,两极用陶瓷膜隔开,阳极区底部充以琼脂(3％)KCl饱和溶液。本法     

甲基绿的电化学行为及其与环糊精形成超分子体系研究

应用“电流法”研究了甲基绿—环糊精超分子体系 ,测定了甲基绿和 4种环糊精的包结常数 .其包结能力为HP_β_CD >β_CD >SBE_β_CD >CM_β_CD ,包结比为 1 :2 (甲基绿 :环糊精 )但甲基绿与α_CD和γ_CD不能形成超分子体系 .此外 ,本文还探讨了甲基绿的电极反应机理 ,初步表明 ,甲基绿在电极上还原的电子转移数为 4 ,有 2个质子参与反应     

酸性溶液中甲基红在钢表面的吸附

甲基红等有机染料类化合物可以作为金属缓蚀剂[1- 2 ] 。本文依据电化学测量结果 ,拟建立一种吸附模型 ,以便于讨论酸性水溶液中甲基红在钢表面的吸附等温式 ,解释甲基红在钢表面的吸附行为及其对钢电化学腐蚀的影响。1　实验部分所用试剂见文献 (2 )。工作电极为钢电极(2 0 #碳钢 ) ,以环氧树脂封涂绝大部分 ,余 0 3ｃｍ2(1 2ｃｍ×0 2 5ｃｍ)作为研究表面。使用前用水磨砂纸磨光亮 ,并用蒸馏水洗净 ,擦干备用。以大面积铂片为辅助电极 ,饱和甘汞电极 (ＳＣＥ)为参比电极 ,试验所测的所有电极电位均是相对于ＳＣＥ的数值。极化曲线、交…     

以1,1,1-三(N-甲基-N_苯基氨基羰甲氧甲基)丙烷为载体的钙离子选择电极

报道了以三脚架化合物1,1,1_三 (N_甲基_N_苯基氨基羰甲氧甲基 )丙烷 (TMPP)为载体的钙离子选择电极的研制;探讨了增塑剂、载体浓度、pH等因素对电极性能的影响 ;结果表明电极对钙离子有较好的近能斯特响应 ,相应的斜率为27.6 mV/pcCa2+ ,线性响应范围为5×10-5 ～5×10-2 mol/L,检出限为2.3×10-5mol/L ;电极在pH4～13范围内具有强的抗干扰能力 ,并具有很好的重复性和稳定性 ;该电极作为钙离子选择电极 ,用于乳酸钙口服液中钙含量的测定 ,取得了满意的结果     

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。     

修饰铂电极-示波双电位滴定法测定Zn(Ⅱ)

制备了锌修饰铂电极,建立了一种新的测定Zn(Ⅱ)的示波双电位滴定法。在六次甲基四胺溶液(1.0mol/L)中(pH=5.5),用制备的修饰铂电极作为双指示电极,以EDTA标准溶液滴定Zn(Ⅱ),利用示波器屏幕上荧光点的显著最大位移指示滴定终点。在3.0×10-4～2.0×10-3mol/L的浓度范围内,Zn(Ⅱ)的回收率为99.9%～100.2%。该修饰电极具有良好的稳定性和重现性,对Zn(Ⅱ,1.0×10-3mol/L)溶液连续11次测定,所得终点电位值均在10.1mV左右,其相对标准偏差(RSD)为0.5%。用来测定含锌的实际样品,其结果与指示剂法测定的值基本一致。     

Nafion—MV修饰电极丙酮酸氧化酶生物传感器测定GPT的研究

用Nafion-甲基紫精修饰电极为基底,以牛血清白蛋白戊二醛为交联剂,将丙铜酸氧化酶固定在电极上,制成丙酮酸氧化酶生物传感器.用这种生物传感器测定人体血清中谷丙转氨酶(GPT)的活性,共存的尿酸、抗坏血酸等电活性物质不干扰测定.测定GPT的活性范围为0～110U/L,响应时间为50s.该传感器具有灵敏度高、抗干扰能力强和响应快等特点.     

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.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

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.     

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.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

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.