电聚吡咯固定化酪氨酸酶电极的制备及性能

在应用恒电位法电化学聚合吡咯的同时,将酪氨酸酶固定在导电聚吡咯膜内,制成一种灵敏、稳定的酪氨酸电极.讨论了溶液pH值和聚合电位对酶固定化的影响,对酶分子嵌入吡咯膜前后的SEM图和CV曲线进行了分析、比较.该电极对甲苯酚响应的线性范围为5.0×10-8～1.0×10-6 mol/L,最适pH值为6.6,酶反应表观上遵循Michaelis-Menten动力学,表观米氏常数为2.2×10-5 mol/L.     

造纸法烟草薄片浆液、白水及成品中铝的测定

采用氟离子选择电极法测定造纸法烟草薄片浆液、白水及成品中的铝。研究了影响测定结果的主要因素,确定了适宜的测定条件。结果表明:当F-的初始浓度为1×10-3mol/L时,电极电位(E)与铝量(ρ)线性关系良好(R=0.9996),线性范围为2.0~10.0μg/mL,回收率为84.71%~88.42%,RSD为0.57%~3.1%。该法通过控制溶液中氟离子浓度从而实现铝的测定,方法适合于样品中铝的分析。     

非平衡态-恒电位配位滴定法同时测定铁和铝

以氟离子溶液作滴定剂，氟离子选择性电极作指示电极，在氟-铝反应没有达到平衡条件下通过恒电位配位滴定法同时测定了铁和铝。控制溶液的pH值为1．5，温度为25℃，硝酸钠离子强度调节剂浓度为0．1mol／L，反应时间为60s。在氟-铁反应达到平衡，但在氟-铝反应没有达到平衡的条件下，采集滴定数据。根据非平衡条件下，响应值的重现性，利用最小二乘法求出常数kFe、kAl及k0，进而计算出铁和铝的浓度。     

离子选择性电极非线性测定水中氟离子的含量

利用氟离子选择性电极测定系列氟离子标准溶液的电极电位(vs.SCE),用测得的电极电位值与氟离子标准溶液的浓度数据进行非线性工作曲线拟舍,可准确测定1×10~(-6)～1×10~(-5)moL/L氟离子溶液的浓度。该法易于实现氟离子溶液的自动连续监测,适于氟离子溶液浓度的在线测量。     

邻苯二酚紫-示波计时电位法间接测定天然水中总酸溶铝

报道邻苯二酚紫（PCV）-示波计时电位法间接测定天然水中的总酸溶铝。在0．5mol/LNH4Ac（pH6．4）缓冲溶液中,PCV在dE／dt－E示波极谱图上出现两个切口,Ep1＝－0．80V和Ep2=-1．20V。加入铝后,切口深度变浅,切口深度的变化△h同加入铝量有关。在最佳条件下,即0．5mol/LNH4Ac,pH6．4及1×10-3mol/LPCV,第二个切口△h2变浅的幅度在4×10－7～4×10-6mol/L铝浓度范围内有线性关系。检测限为2×10-7mol/L。在1×10－6mol/L时标准偏差为8．3％（n=10）。应用该法测定了天然水中总酸溶铝,并同ICP-AES所获结果进行了对照。结果基本一致。     

电聚吡咯固定化酷氨酸酶电极的制备及性能

在应用恒电位法电化学聚合吡咯的同时 ,将酪氨酸酶固定在导电聚吡咯膜内 ,制成一种灵敏、稳定的酪氨酸电极 .讨论了溶液 pH值和聚合电位对酶固定化的影响 ,对酶分子嵌入吡咯膜前后的SEM图和CV曲线进行了分析、比较 .该电极对甲苯酚响应的线性范围为 5 .0× 10 -8～ 1.0× 10 -6mol/L ,最适 pH值为 6 .6 ,酶反应表观上遵循Michaelis_Menten动力学 ,表观米氏常数为 2 .2× 10 -5mol/L .     

离子交换树脂分离富集催化动力学电位法测定痕量钒

研究了在稀硫酸介质中,以痕量钒(Ⅴ)催化溴酸钾氧化碘化钾的反应为指示反应,用碘离子选择电极跟踪Ⅰ-,建立了催化动力学电位法测定钒的方法.在一定的条件下,该指示反应为一级反应,反应速度可用电位的变化△E表示.当时间固定,△E与钒(Ⅴ)浓度在0.015～0.1 mg·L-1范围内呈线性关系.方法的检出限为3.2×10-7g·L-1.该法可用于钢铁样品中钒的测定,试样溶液中钒(VO3-4)预先从弱碱性溶液中(pH 7.0～8.2)用强碱性阴离子交换树脂分离.用1.0 mol·L-1硫酸从树脂上将钒(Ⅴ)洗脱后按所述方法测定.测定结果与标准值相符,相对标准偏差小于5%.     

聚苯胺/钴-氧化钴膜作传感元件的pH传感器的性能

研究了在玻碳电极上修饰不同物质所制得的pH传感器,通过电位滴定的方法比较得出先修饰聚苯胺,再修饰钴-氧化钴膜的电极对pH有较好的响应,能代替玻璃电极应用在实际样品测定中. 探究了最佳修饰条件为:先在0.1 mol/L苯胺的盐酸(1 mol/L)溶液中, 电位范围为-0.2～1.0 V,以100 mV/s 的扫描速率循环伏安扫描10圈修饰聚苯胺膜;接着在含2.0×10-4 mol/L Co2+的磷酸盐缓冲溶液(PBS)(pH=7.5)中,电位范围为-1.2～1.2 V,以100 mV/s的扫描速率循环伏安扫描 5圈修饰钴-氧化钴膜. 得到的修饰电极响应斜率为-61.60 mV/pH,响应范围pH值为0.5～13.     

聚缬氨酸修饰电极在抗坏血酸共存下选择性测定去甲肾上腺素

利用循环伏安法制备了聚缬氨酸修饰电极,在缬氨酸浓度为0.01 mol/L的磷酸盐缓冲溶液(pH=9.0)中,起止电位范围为1.0～2.4 V,以40 mV/s扫描速率循环扫描9周进行聚合. 聚缬氨酸膜对去甲肾上腺素(NE)的电化学氧化具有明显的催化作用. 研究了NE在聚缬氨酸修饰电极上的电化学行为,建立了测定NE的电化学分析新方法. pH值在2.2～8.0范围内,研究了磷酸盐缓冲溶液pH值对NE电化学行为的影响. 结果表明,氧化还原峰电位随pH值升高发生负移;在pH=4.0磷酸盐缓冲溶液中,NE在修饰电极上呈现1对灵敏的氧化还原峰,利用循环伏安法测定NE还原峰电流可排除抗坏血酸(AA)干扰. NE在聚缬氨酸修饰电极上的还原峰电流与其浓度在4.6×10-7～1.1×10-5 mol/L和1.1×10-5～1.2×10-4 mol/L范围内呈良好线性关系;相关系数分别为0.995 7和0.991 8;检出限(S/N=3)为8.0×10-8 mol/L;其回归方程为ipc(A)=6.80×10-7+1.05c,ipc(A)=1.23×10-5+0.16c. 修饰电极具有良好的灵敏度、选择性和稳定性,可用于去甲肾上腺素针剂样品分析.     

双水杨醛缩乙二胺合铜(Ⅱ)席夫碱金属配合物的合成及应用

合成了双水杨醛缩乙二胺合铜(Ⅱ)[Cu(Ⅱ)-EDBSAD]席夫碱金属配合物,并以该配合物为中性载体制备PVC膜电极,该电极对SCN-具有优良的电位响应特性,在pH=5.5磷酸盐缓冲溶液中,SCN-浓度在1.0×10-1～1.0×10-7mol/L之间具有能斯特响应,校准曲线方程为E(mV)=-51.75lg cSCN--255.29,检测下限为5.6×10-8mol/L。将电极用于废水中硫氰酸盐含量的测定,结果与高效液相色谱法基本一致。     

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.     

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.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.