柴胡中柴胡皂甙a的超声辅助溶剂提取

以溶剂提取法为基础,以超声波为辅助手段,对柴胡中的有效成分进行了提取.通过对提取液中柴胡皂甙a量的测定,研究了超声功率、提取温度、提取时间和样品浸渍时间等条件对提取效果的影响,优选出超声辅助溶剂提取的最佳条件为超声功率50%、提取温度50 ℃、提取时间20 min、样品浸渍时间24 h.实验结果表明,超声辅助溶剂提取比普通的溶剂提取具有更高的提取效率.     

植物性食品中有机氯农药残留量检测的前处理方法研究

以丙酮-石油醚为萃取溶剂,采用超声波提取法、涡旋振荡提取法和索氏提取法测定了不同中药材、茶叶和菜干等植物性食品中的六六六、滴滴涕8种异构体有机氯农药残留量,对样品颗粒大小、浸泡时间、回流时间等因素进行了研究.3种前处理技术均有较好的回收率,样品颗粒大小、浸泡时间等对提取效率的影响不明显,检测结果无明显差异.相比较涡旋振荡提取法是一种成本低、耗时短、操作简便的前处理技术.     

野菊花中蒙花苷的提取及其含量的测定

以乙醇为溶剂,采用溶剂回流提取方法结合微波、超声波辅助提取野菊花中的蒙花苷,用HPLC法测定。采用正交试验法研究了野菊花中蒙花苷提取和HPLC实验条件,并比较了采用不同的微波和超声波辅助提取方式对蒙花苷提取结果的影响。结果表明,溶剂回流提取最佳条件为:提取温度80℃,回流时间2.0 h,溶剂用量40 mL。应用于安徽等产地野菊花中蒙花苷的提取分析,结果显示,广东和广西产地药材含量明显更高;在相同的实验条件下采用微波辅助提取可使蒙花苷达到较高的提取率,特别是采用微波辐射药材后再进行溶剂回流提取,提取时间可缩短一半。     

超声波辅助提取柿子树叶单宁的研究

以70%的丙酮溶液为提取溶剂,采用超声波辅助提取野柿叶中的单宁,考察了超声波的功率、提取温度、提取时间等因素对单宁提取量的影响.采用响应面法对提取条件进行优化,并建立了二次回归模型.实验结果显示:当提取温度为52℃、超声波功率为80 W、提取时间为42 min,在此条件下单宁的提取量为203.15 mr/g,比无超声波...     

微波辅助-旋转回流提取仪的组装及其在叶下珠有机酸提取中的应用

组装了一种新型的微波辅助旋转回流装置,该装置的基本原理与微波辅助溶剂萃取的原理相同,但采用了旋转的技术以加速提取.应用该装置以正交实验筛选优化叶下珠中有机酸的提取工艺,并利用毛细管电泳技术分离测定了提取液中有机酸的含量以评价提取效果.最佳提取工艺:乙醚为溶剂,微波功率800 W,提取时间4 min,溶剂用量300 mL.在该提取条件下,平行5次提取叶下珠中丁二酸、原儿茶酸、没食子酸、咖啡酸、阿魏酸的平均含量分别为42.2、103.5、436.2、123.8、67.4 μg/g,相对标准偏差为0.87% ～3.7%,加标回收率为94% ～104%.将该法与常规的微波辅助提取法及回流提取法进行比较,结果表明,微波辅助旋转回流提取法提取效率明显优于其它2种方法.     

快速溶剂萃取柚皮中的黄酮类化合物

采用快速溶剂萃取法从柚子皮中提取出黄酮类化合物,考察了不同的提取溶剂、提取时间、提取温度、循环次数等提取条件下的提取效果,并与微波法、超声波法及索氏提取法进行了对比.结果表明,快速溶剂萃取法提取柚子皮中的黄酮类化合物,在提取溶剂用量、提取时间和提取效率等方面,均优于传统的提取方法,且自动化程度高,为进一步开发利用柚子皮的药用价值提供了参考.     

微波辐射溶剂提取-分光光度法测定农吉利中的总黄酮

采用微波辐射溶剂法提取农吉利中的总黄酮。研究了微波功率、微波辐射时间、提取溶剂用量、提取温度、提取时间等实验条件。以牡荆素作为目标物表征,利用UV法测定了提取液中总黄酮。实验结果表明:与常规溶剂回流提取相比,在相同的提取条件下用微波辐射处理药材后再进行提取,其提取率明显提高,山东和广西样品中总黄酮的提取率分别提高48.3%和23.2%。该方法的加标回收率为94.2%~105.5%,重复测定结果的相对标准偏差为1.1%(n=6)。该法用于农吉利中总黄酮的提取和测定,处理方法简单,测定结果可靠。     

微波间歇萃取-分光光度法测定三七中总皂苷

本文建立了采用微波辅助间歇提取三七样品中的总皂苷,并以分光光度法测定其含量的实验方法。分别通过单因素实验和正交实验设计,优化了萃取溶剂浓度、溶剂用量、微波功率和微波辐射时间等提取条件,确定了微波辅助萃取法提取三七中皂苷类化合物的最佳条件为:使用浓度为60%的乙醇,在液固比100∶1的条件下,以255 W的微波功率,微波间歇萃取10×20 s。在上述最优条件下进行了精密度和回收率实验,加入回收率在97.7%~101.8%之间,RSD为1.54%(n=5)。与传统的索氏提取法和超声波提取法比较,微波辅助萃取法具有操作简便,宽速,重现性好等特点,实验结果表明此方法可推广应用于各类中草药中总皂苷的含量测定。     

超声波提取-气相色谱法测定油田区土壤中21种酚类化合物

采用超声波提取—气相色谱法测定油田区土壤中21种酚类化合物,主要研究了提取时间及净化条件等对测定结果的影响.对比了加压流体萃取与超声波提取方式对回收率的影响,结果表明:超声波提取法回收率优于加压流体萃取法,其中2,4-二硝基酚和4-硝基酚两种化合物比加压流体萃取法回收率提高了30%.以10.0 g土壤样品计,酚类化合物的检出限为0.01～0.05 mg/kg,样品加标回收率为81.5%～110%,精密度为2.6%～11%.经有证标准物质验证,相对误差为2.6%～14%.试验结果表明,超声波提取法适合于油田区土壤中21种酚类化合物的测定.     

烟草中有机氯类农药多残留分析前处理方法对比研究

以烟草中有机氯类农药为研究对象,从检出限、回收率、重复性和色谱图4个方面系统比较了机械振荡萃取法、超声波溶剂萃取法、微波辅助萃取法和加速溶剂萃取法4种常用前处理方法。由于加速溶剂萃取法是在高温高压下进行萃取,在提取出残留农药的同时,也提取出更多的干扰物。机械振荡法、超声波溶剂萃取法和微波辅助萃取法各项结果差别较小,其中机械振荡萃取法回收率和重复性最好,但提取时间较长。考虑溶剂消耗和提取时间等方面的因素,微波辅助萃取是较理想的样品前处理方法。     

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%.     

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.     

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.     

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.     

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.     

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.     

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.     

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.