聚对氨基苯磺酸修饰电极对桑枝中桑色素的灵敏测定

采用电聚合的方法制备了聚对氨基苯磺酸(PABSA)修饰电极,以循环伏安法和差分脉冲伏安法研究了桑色素在该修饰电极上的电化学行为。PABSA和黄酮类药物桑色素的π-π共轭作用使得桑色素在该修饰电极上产生的氧化峰更加灵敏。实验发现,在pH 7.0的磷酸盐缓冲介质中,桑色素在0.214 V处产生灵敏的氧化峰。在优化实验条件下,采用差分脉冲伏安法对桑色素进行定量测定,桑色素的氧化峰电流与其浓度呈良好的线性关系,线性范围为5.0×10-7~1.0×10-3 mol/L,检出限为1.0×10-7 mol/L。将该修饰电极用于桑枝生物样品中桑色素含量的测定,结果满意。该方法具有灵敏度高、重现性好的特点,且该修饰电极稳定性高,可重复使用。     

L-半胱氨酸自组装膜电极对米吐尔的电催化及其分析应用

研究了米吐尔在L 半胱氨酸自组装膜修饰金电极上的电化学行为。米吐尔在该修饰电极上的CV曲线仅出现一对峰 ,其峰形对称 ,ΔEp =42mV ,氧化还原峰电流之比约等于 1,为可逆反应 ;扩散系数D =2 .2 4× 10 - 6 cm2 ·s- 1 。初步探讨了电催化机理。差分脉冲伏安法测定其氧化峰电流与米吐尔浓度在 5 .0× 10 - 7～ 2 .0× 10 - 5mol/L和 5 .0× 10 - 5～ 1.0× 10 - 3 mol/L范围内分段呈线性关系 ;相关系数分别为 0 .9987和 0 .9972 ;检测限 1.0× 10 - 8mol/L     

基于双层类脂膜的去甲肾上腺素传感器

报道了去甲肾上腺素 (NE)在月桂酸 -双层类脂膜修饰的玻碳电极上的电化学行为 ,在 +0.6～ -0.2V(vs.Ag/AgCl)电位范围内 ,于pH7.0的0.01mol/L的KH2PO4-Na2HPO4 底液中 ,去甲肾上腺素产生很灵敏的氧化峰电流。氧化峰电流与去甲肾上腺素浓度在1.7×10 -5～5.9×10 -4mol/L范围内呈良好线性关系。该电极可作为检测去甲肾上腺素的新型高灵敏度电化学生物传感器     

聚吖啶红修饰玻碳电极测定肾上腺素

研究了聚吖啶红修饰玻碳电极的制备及肾上腺素在此修饰电极上的电化学行为.肾上腺素浓度在1.0×10-6～1.0×10-4 mol/L的范围内与其氧化峰电流呈线性关系,回归方程为ip(10μA)=1.160+0.4390c(mol/L),相关系数R=0.9981,检出限是10-7 mol/L.实验结果表明该修饰电极能有效消除抗坏血酸的干扰,方法用于注射液中肾上腺素的检测,其回收率在93.7～100.3%范围内.     

锇联吡啶氧化还原聚合物膜修饰电极对肾上腺素的电催化氧化及安培检测

 用电化学还原方法制备了一种锇联吡啶氧化还原聚合物(POs-EA)膜修饰电极,并研究了其在磷酸缓冲溶液中的电化学行为和对肾上腺素的电催化氧化作用. 结果表明,该修饰电极表现出较为可逆的伏安响应并对肾上腺素的电化学氧化具有良好的电催化性能. 与裸金电极相比, POs-EA膜修饰电极大大提高了肾上腺素的峰电流,降低了肾上腺素的氧化峰电位. 初步探讨了该电极上肾上腺素的电催化氧化机理. 通过检测外加电位为0.29 V时的氧化电流对肾上腺素进行检测,结果表明,其氧化电流和肾上腺素的浓度在5×10-8～1×10-5 mol/L范围内呈良好线性关系,检测限可达1.5×10-8 mol/L.     

基于羧基化多壁碳纳米管修饰玻碳电极快速检测氨基脲的研究

基于羧基化多壁碳纳米管修饰的玻碳电极(CMWCNTs/GCE),构建了一种灵敏检测氨基脲(SEM)的电化学传感器.采用傅里叶变换红外光谱、透射电子显微镜、电化学阻抗谱对修饰材料进行表征.结果表明,羧基化的多壁碳纳米管出现羧基碳氧双键的红外特征峰,管径明显减小,长度变短,电化学阻抗值显著减小.在1 mol/L HAc-NaAc缓冲液中,利用循环伏安法和时间-电流曲线研究了SEM在CMWCNTs修饰电极上的电化学行为.SEM在修饰电极上呈现不可逆的氧化峰.与裸电极相比,氧化峰电流明显增大.在最佳实验条件(pH 7.0,扫描速度为0.1 V/s)下,测得SEM在5.00×10-6~1.09×10-3mol/L浓度范围内与氧化峰电流呈线性关系,线性方程为IP(μA)=-0.472+0.0599C(μmol/L),相关系数r=0.997,检出限为1.88×10-7 mol/L(S/N=3).在实际猪肝样品检测中加标回收率为92.8%~98.0%.     

聚对氨基吡啶化学修饰电极上酚磺乙胺的电化学行为及其溶出伏安法测定

在玻碳电极上制备了聚对氨基吡啶 (POAP)修饰膜电极 ,并用POAP电极研究了酚磺乙胺 (DIC)的电化学行为。POAP修饰电极对DIC的氧化有良好的电催化活性。循环伏安图上出现一对灵敏、可逆的氧化还原峰。在最佳条件下 ,氧化峰电流与DIC浓度在 4.0× 10 -8～ 1.0× 10 -3 mol/L范围内呈良好线性关系 ,开路富集 5min检测限达 7.6× 10 -10 mol/L。用POAP测定DIC具有良好的重现性、灵敏度和稳定性     

介孔炭/纳米金修饰玻碳电极的制备及其应用研究

制备了介孔炭/纳米金修饰玻碳电极,并对对苯二酚(HQ)在该修饰电极上的电化学行为进行了研究。与HQ在纯介孔炭材料修饰玻碳电极上的电化学响应相比,HQ在该修饰电极上的氧化峰和还原峰电流均大大增加,表明纳米金与介孔炭复合后对HQ具有良好的催化作用。HQ在该修饰电极上经过富集后,峰电流明显增大。采用循环伏安法对HQ电化学行为进行研究,结果表明,HQ在3.0×10-8~1.0×10-6mol/L和1.0×10-6~1.0×10-4mol/L浓度范围内与峰电流呈良好的线性关系,据此建立了检测HQ的电化学分析方法。该方法的相对标准偏差为0.69%,检出限(S/N=3)为1.0×10-8mol/L,具有较高的稳定性和灵敏度。     

抗坏血酸在离子液体修饰玻碳电极上的电化学行为

利用离子液体1-丁基-3-甲基咪唑四氟硼酸盐(BMIMBF4)对玻碳电极(GCE)进行修饰,制备了BMI-MBF4/GCE电极.在0.1mol/L的磷酸盐缓冲溶液中,采用循环伏安法研究了抗坏血酸在BMIMBF4/GCE电极和裸玻碳电极(GCE)上的电化学行为.结果表明,pH=5.7的磷酸盐缓冲溶液为最佳测定底液,最佳富集时间为120s;BMIMBF4/GCE对抗坏血酸的氧化反应有很好的电化学催化作用.抗坏血酸的氧化峰电流与其浓度在2.0×10-4～1.0×10-2 mol/L的范围内呈良好的线性关系,相对标准偏差为4.53%(n=5).     

聚氨基磺酸修饰玻碳电极在抗坏血酸共存时测定肾上腺素

研究了聚氨基磺酸修饰玻碳电极的制备及肾上腺素和抗坏血酸在此修饰电极上的电化学行为。在磷酸盐缓冲液pH为 7. 0的条件下,肾上腺素在修饰电极上呈现 2个氧化峰和 1个还原峰。其峰电位都随着pH值的增加而负移。当肾上腺素与抗坏血酸共存时,EP较正处氧化峰电位与AA氧化峰电位差达 190mV。肾上腺素氧化峰电流与其浓度在 1. 0×10-7 ~1. 0×10-4 mol/L的范围时呈良好的线性关系,其线性回归方程为ip(10μA) = 1. 455 + 0. 3765C(mol/L), 相关系数r=0. 9977,检出限为 1. 0×10-8 mol/L。实验结果表明:该修饰电极能同时测定肾上腺素和抗坏血酸; 100倍的马尿酸、半胱氨酸、柠檬酸不干扰测定。方法用于注射液中肾上腺素的检测,结果令人满意。     

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.     

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.     

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.     

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%).     

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.     

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.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

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.