分散液液微萃取技术及其在生物样品分析中的研究进展

分散液液微萃取是一种新型微萃取技术,具有易操作、低成本、耗时短、环境友好、萃取效率高等优点。该文着眼于分散液液微萃取技术中萃取剂的性质及辅助分散方式,综述了常规分散液液微萃取、离子液体分散液液微萃取、超声辅助分散液液微萃取等多种萃取模式,并重点归纳总结了近5年分散液液微萃取技术在生物样品分析领域的应用进展。     

分散液液微萃取技术在食品分析中的应用进展

近年来,分散液液微萃取作为一种新型液相微萃取(LPME)技术受到广泛关注。该技术具有操作简单、有机溶剂用量少、富集倍数高等显著优点,已被广泛用于各类样品基质中无机和有机分析物的提取。但由于传统分散液液微萃取技术的萃取剂以高毒性有机溶剂为主,且选择性差,从而严重限制了该技术的应用。为此,最近几年发展了许多操作模式,如低密度萃取剂分散液液微萃取、悬浮固化分散液液微萃取、调节萃取剂密度的分散液液微萃取、离子液体-分散液液微萃取、水溶液作为萃取剂的反相分散液液微萃取等。该文综述了分散液液微萃取技术原理、萃取过程和影响因素(如萃取剂与分散剂种类和体积、p H值、离子强度、萃取时间等),并对其在食品分析中的应用进展进行了系统总结。     

分散液液微萃取-气相色谱法测定水样中甲拌磷农药

建立了基于分散液液微萃取(DLLME)的新型样品前处理方法,并采用气相色谱/氢火焰离子化检测器对水样中痕量的甲拌磷农药进行了测定。考察了影响分散液液微萃取的因素包括萃取溶剂、分散剂、样品体积、萃取温度和离心速度等。在最佳实验条件下,对甲拌磷的富集倍数达到300倍;检出限为0.001μL/L;方法的线性范围为0.01~10μL/L,R2为0.9986;相对标准偏差为6.65%;回收率为104%。将分散液液微萃取法与单滴液相微萃取和离子液体-液相微萃取方法进行了对比,结果表明,分散液液微萃取技术具有操作简单、快捷(前处理时间小于5 min)、富集效果好、回收率高等优点。同时预言,将离子液体与分散液液微萃取结合,将会产生更加满意的结果。     

金属检测中新型前处理技术研究进展及应用

精准检测环境和食品中金属含量对环境保护和人体健康至关重要.样品的准备环节是造成样品损失和二次污染的关键步骤, 因此合适的前处理方法可以提高金属分析的选择性和灵敏度.从液相萃取和非液相萃取新技术两方面综述了浊点萃取、离子液体、超分子溶剂-分散液液微萃取、顶空固相微萃取技术、超临界流体萃取特点及在复杂样品前处理中的应用和研究进展, 并对其未来发展方向进行了展望.     

分散液液微萃取富集土壤中的二嗪磷和甲拌磷残留

建立了基于离子液体1-辛基-3-甲基咪唑六氟磷酸盐的分散液液微萃取富集土壤中二嗪磷和甲拌磷的方法。实验确定了萃取优化条件:萃取剂为400μL 1-辛基-3-甲基咪唑六氟磷酸盐离子液体,分散剂为4mL甲醇,液固比(溶液体积与样品质量之比)为4∶1,微波温度为50℃,微波时间为8min。将建立的萃取方法与高效液相色谱法结合,应用于实际土壤样品的测定,结果表明该方法能对土壤中的二嗪磷和甲拌磷进行高效萃取与富集,方法快速简便。     

分散固相萃取-超声辅助分散液液微萃取/高效液相色谱法测定土壤中溴氰菊酯残留

建立了以分散固相萃取-超声辅助分散液液微萃取为样品前处理技术,结合高效液相色谱法(HPLC)测定土壤中溴氰菊酯。样品用甲醇∶水(1∶4,V/V)提取,经布氏漏斗减压抽滤,滤液经N-丙基乙二胺(PSA)、C18、石墨炭黑粉(GCB)净化后,用氯仿萃取,超声,离心后沉积相进行HPLC测定。对分散固相萃取吸附剂的选择及影响分散液液微萃取的因素进行了优化,在最优条件下,溴氰菊酯的富集倍数达到565倍,线性范围为0.005~2.5mg/kg,线性相关系数为0.9998,检出限为0.001mg/kg,平均加标回收率为70.3%~94.5%,相对标准偏差为2.5%~4.7%。该方法具有简便快速、准确灵敏、萃取效率高等特点,可用于土壤中溴氰菊酯残留检测。     

温控离子液体分散液液微萃取结合高效液相色谱法检测脐橙中染色剂残留

建立了QuEChERS-温控离子液体分散液液微萃取结合高效液相色谱法快速检测脐橙中5种染色剂残留的分析方法。QuEChERS前处理步骤:样品用乙腈快速提取,NaCl和无水MgSO4除水后,经N-丙基乙二胺净化。温控离子液体分散液液微萃取步骤:QuEChERS前处理的净化液(1 mL)为分散剂,1-辛基-3-甲基咪唑六氟磷酸盐离子液体(60μL)为萃取剂,55℃水浴12 min,将目标物富集。用高效液相色谱-紫外检测器分析,检出样品用超高效液相色谱-串联质谱确证。在0.01和0.05 mg/kg的添加水平下,5种染色剂的平均回收率为70.3%~93.6%,相对标准偏差为3.5%~9.2%,定量限为1.1~2.8μg/kg。     

离子液体在微萃取技术中的应用

离子液体是在室温或近于室温下呈液态的熔盐体系,由特定阳离子和阴离子构成。与传统的液态物质相比,离子液体几乎没有蒸气压、不易挥发、能溶解许多无机物和有机物。在样品前处理技术中得到了广泛的应用。微萃取技术是一种简便快速、提取效率高、溶剂用量少、环境友好的样品前处理技术。本文综述了离子液体在微萃取技术(液相微萃取和固相微萃取)中的应用。     

分散液-液微萃取在有机化合物和金属离子分析中的应用进展

综述了分散液-液微萃取的基本原理和萃取过程,介绍了萃取剂、分散剂、螯合剂的浓度、萃取时间、pH值、盐效应、共存离子等因素对萃取效果的影响,评述了分散液-液微萃取技术在有机化合物和痕量金属离子分析中的应用情况,引用文献42篇。     

离子液体在微萃取方面的应用进展

离子液体具有蒸汽压低、热稳定性好、溶解性能高、可设计性和多样性等特性,使其在萃取尤其是微萃取方面得到迅速发展和应用.而在单滴微萃取、分散液相微萃取、液-液-液微萃取和固相微萃取中,离子液体更以其较大的粘度、密度及非挥发性等特性,使得微萃取技术更容易操作,无有机溶剂污染,方法的灵敏度更高,且扩展了微萃取的应用范围.文章综述了近年来离子液体在液相微萃取和固相微萃取方面的应用进展,并对其发展趋势进行了展望.     

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%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

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.