带电溶质在电色谱中柱内富集方法的研究————-基本理论 模型和实验验证

在电色谱(CEC)中引入场增强进样技术,并与HPLC柱内富集技术结合以使带电溶质得到更好的富集效果。理论研究表明,采用较高电阻率的样品溶剂,及匹配适当的有机调节剂强度有利于带电溶质在CEC中的柱内富集,以碱性药物普罗帕酮为实验样品,采用水(φ＝40%)-乙腈(φ=60%)为样品溶剂,水(φ=15%)-乙腈(φ=85%)-Tris(2mmol/L)-TEA(0.6mmol/L,pH7.60)为运行缓冲溶液时,达到了17,000倍以上的富集效果,从理论和实验研究的角度说明了CZE与HPLC机制结合的CEC进样方法用于样品柱内富集的可行性,进一步讨论了各种操作条件对富集结果的影响规律。     

酞酸酯的场增强样品进样-微乳液毛细管电动色谱分析

建立了场增强样品进样–微乳液毛细管电动色谱(microemulsion electrokinetic chromatography,MEEKC)分析6种酞酸酯的方法,对影响富集过程的因素进行了考察。最佳富集条件为:以压力进样先进一段水柱(5.52 kPa×500s),在富集电压为-15 kV下,样品以电动方式进样富集,样品基质为30mmol/L胆酸钠+30.0 mmol/L硼砂(pH 8.5)。与常规MEEKC方法相比,场增强样品进样在线富集技术使6种酞酸酯的检测灵敏度提高了1.6～1000倍,检测限(S/N=3)为1～500 ng/mL。所建立的方法用于食品塑料袋中酞酸酯的测定,加标回收率为92.5%～112.2%。     

阳离子选择性耗尽进样-胶束扫集法测定尿液中的麻黄碱和可待因

联用选择性耗尽进样和胶束扫集两种在线富集技术,建立了尿样中麻黄碱和可待因含量测定的灵敏方法,并通过日内、日间、柱间实验考察了方法的稳定性.胶束扫集电动色谱缓冲体系为80 mmol/L 十二烷基磺酸钠(SDS)-20 mmol/L NaH2PO4(pH 2.20)-18%乙腈(V/V),分离电压-20 kV,进样电压10 kV,进样时间150 s,测量波长200 nm.同时讨论了pH值、SDS浓度、选择性耗尽进样萃取液电导、进样电压、进样时间和进水长度等对分离效果的影响.结果显示,方法富集功能很强,对麻黄碱和可待因含的富集倍数分别达5800和2490以上.在优化条件下,方法线性关系良好(r=0.9999),麻黄碱和可待因的线性范围分别为0.500～16.0 μg/L和2.00～48.0 μg/L,检出限分别为0.10和0.80 μg/L.方法稳定性良好,日内、日间和柱间的RSD分别为2.6%,5.9%和6.6%.应用于实际尿样分析,回收率在96.8%～106%之间,RSD≤4.7%,结果比较满意.     

大体积进样-乙腈盐堆积-胶束扫集毛细管电动色谱法对马来酸氯苯那敏的测定

建立了大体积进样-乙腈盐堆积-胶束扫集毛细管电动色谱法测定马来酸氯苯那敏片中马来酸氯苯那敏的新方法,并考察了样品中乙腈和NaCl浓度对分离效果的影响.结果表明,以12 mmol/L四硼酸钠-50 mmol/L硼酸- 50 mmol/L十二烷基硫酸钠(SDS)为缓冲液(含10%甲醇,pH9.1),以70%乙腈- 200m...     

溶剂棒微萃取-HPLC法快速测定常用蔬菜中的痕量尼古丁

建立了一种以溶剂棒微萃取为样品前处理技术,HPLC/UV法测定常用蔬菜中痕量尼古丁的方法。系统优化了溶剂棒微萃取条件以及HPLC法测定尼古丁的相关参数,方法的线性范围0.005~1 mg/L,相关系数为0.9999;检出限0.002 mg/L(S/N=3);在优化的实验条件下对尼古丁的富集倍数可达190倍。样品加标回收率72%~111%(除黄瓜加标样品为47%),相对标准偏差小于10.0%(n=3)。实验证明,本方法可用于常用蔬菜中痕量尼古丁的有效富集、测定。     

毛细管区带电泳中场增强进样柱内富集的非线性特征

直接柱头场效应进样是一种毛细管区带电泳柱内富集,其进样过程中样品在柱内的分布可分为两部分,即在运行缓冲溶液中的堆积区段和由电渗流引入的样品溶液区段.通过对溶质输运行为的研究表明:两区段长度与进样时间之间并非简单的线性关系,因此进样量与进样时间的关系也非线性,且与溶质淌度有关;进样量的增加并不能导致富集倍数的同步增加,由于层流的作用使得场效应进样柱内富集效果降低.为了在保持柱效基本不变情况下得到好的富集效果,除需使溶质在运行缓冲溶液和样品溶液中的电导率比极大外,进样时间也应与之匹配.     

中性溶质在MEKC中柱内富集的理论研究

毛细管电动力学色谱(MEKC)中通过“扫”的技术可以使样品组分在线富集。本研究基于柱分离过程弛豫理论的基本方法,对溶质在MEKC中柱内输运过程加以研究,得到了描述进样长度及样品区带和运行区带性质差别对富集效果影响的理论表达式。通过对进样长度及溶质在两区带中的容量因子与富集效果之间关系的进一步探讨,证实溶质在胶束中的溶解度是影响富集的最重要因素;在基本不影响分离效果的情况下,适当加大进样长度一般对富集有利。     

通过柱切换技术与高效液相色谱联用的限进性柱对盐酸贝那普利的在线富集性能

以自制的限进性填料柱为预处理富集柱,Luna C₁₈柱为分析柱,通过柱切换技术将限进性填料柱与高效液相色谱联用(RAM-HPLC),研究了盐酸贝那普利的在线富集效果。考察了进样体积与峰面积、系统总压力的关系,以及常规进样与大体积进样的差别。当进样体积在100 μL以内时,峰面积随进样体积的增加而增加;当进样体积大于80 μL时,系统总压力变化明显。考虑对整个系统的保护,选择80 μL作为最大进样体积。同一浓度的样品进样20 μL与进样80 μL所得峰面积之间的线性关系良好。RAM柱对盐酸贝那普利具有良好的富集作用,能够有效提高HPLC的灵敏度,而且具有简单、经济的特点。     

非水毛细管电泳/紫外检测法测定肉桂中的肉桂酸和肉桂醛

建立了用非水相体系高效毛细管电泳/紫外检测法同时测定肉桂酸和肉桂醛的新方法,考察了运行电压、非水相介质和电解质等因素的影响。在25℃下,以乙腈和碳酸丙烯酯(体积比3∶2)的混合液为缓冲体系的溶剂,缓冲体系中含25 mmol/L十六烷基三甲基溴化铵,0.375%(φ)乙酸,以碳酸丙烯酯为样品溶剂,重力进样30 s,运行电压20 kV,毛细管总长45 cm,有效长度30 cm,φ75μm,检测波长310 nm。肉桂酸线性范围为4~100 mg/L,r=0.999 4,检出限为0.80 mg/L,RSD为1.07%。肉桂醛的线性范围10~240 mg/L,r=0.999 6,检出限为2.30 mg/L,RSD为2.19%。应用于肉桂中的肉桂醛和肉桂酸的测定,结果满意。     

利用瞬间等速电泳的毛细管区带电泳大体积电动进样的研究

采用添加乙腈引发的场放大进样与瞬间等速电泳结合的预富集方法,实现了在毛细管内大体积高盐样品中阳离子的有效富集与分离。详细讨论了影响富集的缓冲体系、尾随离子种类、毛细管有效长度、进样时间和等速电泳时间等重要因素。选择在400 mmol/L LiAc-HAc缓冲液(pH 4.5)和400 mmol/L　β-丙氨酸-HAc尾随液(pH 4.5)及10 kV下样品和尾随溶液电动注入时间分别为270和90 s的条件下对高盐溶液中两种结构相近的药物普萘洛尔和美托洛尔进行了富集和分离。该方法富集倍数约为常规电动进样的280倍,普萘洛尔和美托洛尔的检出限分别为2×10-3和8×10-3 mg/L。     

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%.     

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.     

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.     

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

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.