中性溶质在反相毛细管电色谱中的保留行为

 分别在以甲醇、乙腈、异丙醇和四氢呋喃为有机改性剂的４种二元流动相体系中对中性溶质在反相毛细管电色谱中的保留行为进行了研究。不仅考察了有机改性剂的种类和浓度对电渗淌度的影响，而且建立了溶质容量因子与有机改性剂在流动相中体积分数间的定量关系，此外还对样品在反相毛细管电色谱和反相毛细管高效液相色谱中的保留行为进行了比较，发现中性溶质在这两种分离模式中的容量因子基本相同。     

多肽的反相梯度加压毛细管电色谱分离

以C18为固定相，采用电压和压力联合驱动流动相，研究反相加压毛细管电色谱分离多肽；考察了加压电色谱中，电压对带电和中性物质迁移的影响，实现了梯度加压毛细管电色谱分离6种多肽；结果表明，加压电色谱可以很好地抑制气泡形成，实验结果准确，重复性好；梯度加压毛细管电色谱在复杂样品的分离分析中，具有很大的潜力。     

硅胶填充柱反相洗脱毛细管电色谱研究

在７５μｍ（ｉ．ｄ．）×２７／２０ｃｍ的硅胶（３μｍ）填充柱上，以乙腈（９５：５）－Ｔｒｉｓ／ＨＣｌ缓冲液（ｐＨ８．３）为流动相，实施毛细管电色谱并对其保留机理进行了研究。研究表明，当采用反相洗脱时，硅胶填充柱显示出阳离子交换和正相分配双重保留机理。同时还对电渗流和热效应进行了研究。     

天冬酰胺修饰硅胶极性固定相的制备

硅胶是最常用的色谱固定相填料.毛细管电色谱(CEC)广泛地使用反相硅胶填料分离中性和非极性物质.极性和碱性物质由于在反相填料上色谱保留很小或不保留,对这些物质的分离长期以来一直是毛细管电色谱反相分离模式的挑战~([1,2]).     

亚微米中孔SBA-15 棒状固定相在毛细管电色谱分离中的应用(英文)

采用中孔SBA-15棒状硅胶颗粒填充毛细管柱用于毛细管电色谱(CEC)分离。这一亚微米材料直径为400 nm并具有沿相同方向伸展的高度有序、均一的圆柱形中孔。棒状的特殊形态使得填充柱的通透性良好,简化了尺寸微小的CEC柱的填充过程。修饰后的棒状SBA-15填充毛细管柱成功应用于反相和离子交换电色谱分离非极性和极性样品,获得了较高柱效(140000理论塔板/m)。流速3.2cm/min时获得最低理论塔板高度为7.1 mm。范迪米特曲线说明了SBA-15孔结构的传质阻力特征。分别以芳香酸、人参、天麻提取物为样品,对亚微米固定相毛细管电色谱柱加以评价。该固定相显示出了较高的分离能力,为纳米材料在色谱固定相中的应用提供了一个新的思路。     

痕量脑啡肽的毛细管电色谱分析技术研究

加压毛细管电色谱为近年来发展起来的一种高效、快速的新型微柱分离方法.亲水毛细管电色谱相较于反相色谱(RPC)和正相色谱(NPLC),在分离极性化合物时,有其独特优势~([1,2]).最近,基于极性固定相的亲水作用毛细管电色谱(HICEC)备受关注,是当前色谱微分离技术的研究热点.     

高效细内径毛细管电色谱填充柱的制备

 发展了一套毛细管填充柱制备方法，在１００μｍ内径毛细管柱中填充３μｍＯＤＳ固定相，以毛细管电色谱法（ＣＥＣ）分离模式对芳香胺类样品进行分离，柱效高达２５．９万理论塔板数／米，折合塔板高度达１．３。类似研究在国内尚未见报道。     

毛细管电中中性溶质在氰基柱上分离机理的研究

 对中性溶质在氰基柱上的毛细管电色谱（CEC）分离特征进行了研究 ,讨论了流动相中有机调节剂种类及其体积分数、缓冲液种类等对溶质迁移速率的影响。通过对样品在氰基柱上的分离行为与其在反相ODS柱和正相SI柱上的分离行为的比较 ,说明中性溶质在氰基柱上的分离机理既具有部分反相特征又具有部分正相特征。受两种机理的影响 ,在不同的操作条件下极性不同的中性溶质在氰基柱上的迁移速率差别很大 ,较一般的正相和反相电中更易出现出峰顺序变化的现象 ,也说明这种分离模式更易于进行分离选择性调节。     

使用含离子涂层柱的毛细管电泳和毛细管电色谱的研究进展

 毛细管电色谱是近年发展起来的高效、高选择性的微分离技术。与一般的毛细管电泳和使用ODS反相填料的毛细管电色谱相比 ,含离子涂层柱的毛细管电泳和毛细管电色谱能提供较大且可控的电渗流 ,便于拓宽分离对象 ,优化分离条件。对使用含离子涂层柱的毛细管电泳和电色谱的特点、发展和应用状况进行了综述。     

毛细管电色谱分析苯氧羧酸类药残的研究

毛细管电色谱(CEC)是近年发展起来的一种高效、快速微柱分离方法,主要分为填充毛细管电色谱,开管毛细管电色谱和整体式毛细管电色谱.开管毛细管电色谱无柱塞和填料,不易产生气泡,且无涡流扩散,能获得较高柱效,其电渗流流速比填充柱大60%,适用于快速分析,具有良好的应用前景.     

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.