毛细管电泳-电化学检测测定茶叶中咖啡因、表儿茶素和抗坏血酸

高效毛细管电泳电化学检测同时测定了6种茶叶中的咖啡因、表儿茶素和抗坏血酸的含量,考察了实验参数对分离、检测的影响。在最佳实验条件下,以300 靘直径的碳圆盘电极为检测电极,检测电极为1.20 V(vs.SCE),在25 mmol/L硼酸盐25 mmol/L磷酸盐(pH 7.6)的混合运行缓冲液中,上述各组分在16 min内能完全分离。咖啡因、表儿茶素和抗坏血酸在2×10-3mol/L～１×10-5 mol/L、5×10-5mol/L～5×10-7mol/L、2×10-4 mol/L～1×10-5mol/L范围内呈线性关系,检测下限分别为6×10-6mol/L、4×10-7mol/L和1×10-6mol/L。该法直接用于茶叶中咖啡因、表儿茶素和抗坏血酸的测定,结果令人满意。     

黄芩及其制剂中黄芩素和黄芩甙的

用毛细管区带电泳 -电化学检测法测定了黄芩及其制剂中黄芩素和黄芩甙的含量。研究了电极电位、电解液酸度和浓度、电泳电压及进样时间等对电泳的影响 ,得到了较为优化的测定条件。以直径为300μm的碳圆盘电极为检测电极 ,电极电位为0.90V(vsSCE) ,在100mmol/L硼酸盐缓冲液(pH9.0)中 ,上述两组分在8min内完全分离。黄芩素和黄芩甙浓度与电泳峰电流分别在5.0×10 -7～1.0×10 -3mol/L和1.0×10 -6～1.0×10 -3mol/L范围内呈良好线性 ,检出限分别为2.24×10 -7mol/L和5.48×10 -7mol/L。7次测定分别含5.0×10 -4mol/L黄芩素和黄芩甙试样溶液 ,峰高的相对标准偏差分别为3.53%和4.03%。     

散利痛中扑热息痛和异丙基安替比林的毛细管区带电泳电化学检测法测定

毛细管区带电泳 -电化学检测法同时测定散利痛片中有效成分扑热息痛和异丙基安替比林的含量 ;研究了电极电位、电解液浓度和酸度、电泳电压及进样时间等对电泳的影响 ,得到了最优化的测定条件 ;以直径为300μm的碳圆盘电极为检测电极 ,工作电极电位为1.0V(vsSCE) ,在50mmol/L硼砂 -NaOH(pH9.35)运行缓冲液中 ,上述两组分在8min内完全分离 ;扑热息痛和异丙基安替比林线性范围分别为2×10-3～5×10 -6mol/L和2×10 -3～2×10 -6mol/L,检出限分别为5×10 -6mol/L和2×10 -6mol/L ;7次平行进样的相对标准偏差(RSD)为3.5%和1.8 % ,加标回收率(n=3)分别为101 %和98% ,该法灵敏可靠 ,结果令人满意。     

丝氨酸织组膜电极的研究

利用猪肝组织膜配合氨气敏电极,研制了丝氨酸生物催化传感电极。丝氨酸浓度的测定范围为5.1×10~(-5)～3.2×10~(-3)mol/L,检出限为3.1×10~(-5)mol/L。研究和讨论了电极的最佳工作条件,并测定了实验条件下酶催化反应的米氏常数Km。该电极用于合成样品分析,效果满意。     

毛细管电泳电化学检测法测定胡黄连中香草酸和阿魏酸的含量

采用毛细管电泳电化学检测法测定了胡黄连中香草酸和阿魏酸的含量 ;研究了电极电位、运行缓冲液的浓度和酸度、电泳电压及进样时间等对电泳的影响 ,得到了最优化的测定条件 ;以直径为300μm的碳圆盘电极为检测电极 ,工作电极电位为0.8V(vs.SCE) ,在50mmol/L硼砂(pH8.4)运行缓冲液中 ,上述两组分在8min内完全分离 ;香草酸和阿魏酸线性范围分别为5×10-4～1×10-6 mol/L和1×10-3～1×10-6 mol/L ,检出限分别为4.2×10 -7和3.0×10 -7mol/L ;7次平行进样的相对标准偏差(RSD)为2.2 %和2.8 % ,回收率(n=3)分别为99%和103 % ,该法灵敏可靠 ,结果令人满意。     

微渗析-液相色谱电化学检测法测定全血中的半胱氨酸和谷胱甘肽

采用微渗析取样作为样品预处理技术,与高效液相色谱电化学检测联用,建立了一种测定血中半胱氨酸(Cys)和谷胱甘肽(GSH)的新方法。电化学检测以玻碳电极为工作电极,结果表明在3.5×10-6～1.0×10-3mol/L浓度范围内,Cys和GSH的浓度分别与氧化峰的峰电流呈良好的线性关系,线性相关系数分别为0.9971和0.9982,检测限分别为1.2×10-6mol/L和3.2×10-6mol/L。     

基于尼古丁对胆碱氧化酶的抑制作用测定尼古丁的研究

基于尼古丁对胆碱氧化酶(CHOD)的抑制作用,将胆碱氧化酶电极用于微量尼古丁的测定。酶电极制作中,先在铂电极表面修饰一层壳聚糖膜,再用戊二醛交联CHOD。采用这种酶固定化方法,电极在4. 0×10-6 ~ 3×10-3 mol/L胆碱的浓度范围呈线性关系。探讨了工作电位、pH、底物浓度等实验条件对酶电极性能及抑制过程中响应电流的影响,测定了电极的重现性、干扰及使用寿命。电极检测尼古丁的线性范围为1. 5×10-5 ~3×10-3 mol/L;检出限为1. 25×10-5 mol/L。将电极用于实际样品烟草中尼古丁回收率的测定,结果良好。     

血红蛋白模拟过氧化物酶催化反应体系的极谱分析

用极谱分析法研究了血红蛋白催化H2O2氧化邻苯二胺(OPD)的反应体系.血红蛋白具有类似过氧化物酶的功能,它能够催化OPD-H2O2的反应生成一种具有电化学活性的产物,该产物在滴汞电极上-0.64V(vs.SCE)产生一个峰形良好的极谱还原峰.优化了血红蛋白的催化反应条件和催化反应产物的极谱测定条件 在最佳条件下,该体系可用于血红蛋白含量的测定,线性范围为2.0×10-9～2.0×10-7mol/L,检测限为1.0×10-9mol/L;也可用于痕量H2O2的测定,线性范围为1.0×10-6～2.0×10-4mol/L,检测限为1.0×10-6mol/L.     

纳米石墨烯修饰电极电化学发光法测定盐酸氯丙嗪的研究

基于盐酸氯丙嗪对联吡啶钌电化学发光的增敏作用,以石墨烯(Graphene)和Nafion复合膜修饰的玻碳电极(GCE)为工作电极,建立了一种直接测定盐酸氯丙嗪的电化学发光新方法。最佳实验条件下,盐酸氯丙嗪浓度在8.0×10-7 ~1.2×10-4 mol/L范围内与其相对发光强度呈良好线性关系(r=0.998 8),且在该修饰电极上的检出限(S/N=3)为4.0×10-7 mol/L。连续测定4.0×10-6 mol/L盐酸氯丙嗪溶液11次,发光强度值的相对标准偏差(RSD)为1.4%,表明该修饰电极具有较好的重复性和灵敏度。盐酸氯丙嗪的加标回收率为93%~104%,RSD(n=5)为4.1%。将该方法应用于药片中盐酸氯丙嗪的检测,结果满意。     

混合香蕉组织碳糊生物微电极的研究及在活体分析中的应用

我们研制了混合香蕉组织碳糊生物微电极,用于神经递质多巴胺(DA)的测定,研究了DA在该电极上的伏安特性及最佳工作条件。该电极选择性好,可抗256倍维生素C(V_(?))的干扰;灵敏度高,检出下限为3.3×10~(-8)mol/L。用于活体分析鼠脑纹状体中DA,线性范围为1.9×10~(-6)～1.3×10~(-4)mol/L(静置时间为10s)。     

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.     

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.     

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.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

Highly efficient and stereoselective cycloaddition of nitrones to indolyl- and pyrrolylacrylates

The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (CH?O) and moderate (NH?N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities.     

Transition metal-free direct amination of benzoxazoles using formamides as nitrogen sources

A transition metal-free method for the direct amination of benzoxazoles using formamides as nitrogen sources is reported, which was mediated by an inexpensive and environmentally friendly tetrabutylammonium iodide/tert-butyl hydroperoxide system and gave the 2-aminobenzoxazole derivatives with moderate to good yields.     

l-Proline-catalyzed five-component domino reaction leading to multifunctionalized 1,2,3,4-tetrahydropyridines

Multifunctionalized 1,2,3,4-tetrahydropyridines are concisely synthesized in good yields via l-proline-catalyzed or l-proline/FeCl₃-cocatalyzed one-pot multicomponent reactions (MCRs). The MCRs involve a domino hydroamination/prins reaction/Mannich-type reaction/intramolecular dehydration-cyclization process. The molecular structure of 5baa, one of multifunctionalized 1,2,3,4-tetrahydropyridines, was confirmed by single-crystal X-ray diffraction.     

Exploring the scope of the Gewald reaction: Expansion to a four-component process

An efficient four-component reaction was developed to take advantage of the reactivity of the 2-aminothiophene-3-carbonitrile functionality, which is obtained during the classical three-component Gewald reaction. Various α-methylene bearing ketones were reacted with malononitrile, elemental sulfur, and aryl/heteroarylnitrile derivatives in t-BuOH/NaOH to afford 2-arylthieno[2,3-d]pyrimidin-4-amines in high yields. Preliminary studies revealed the photophysical properties of the products and their potential for use as metal sensors.