顶空固相微萃取-气相色谱-质谱联用分析麦冬中有机挥发物

采用顶空固相微萃取-气相色谱-质谱联用(HS-SPME-GC-MS)分析麦冬中挥发性成分,对萃取温度、时间、脱附时间及样品用量等条件进行了优化,方法所得结果与同时蒸馏萃取-气相色谱-质谱联用(SDE-GC-MS)方法比较,相对含量较高的成分基本一致.固相微萃取方法可应用于麦冬中有机挥发性成分的快速分析.     

顶空固相微萃取-气相色谱-质谱法快速测定酱油中的挥发性风味成分

建立了一种快速简便地测定酱油中挥发性风味成分的顶空固相微萃取（HS-SPME）-气相色谱-质谱法(GC-MS)。以2-辛醇为内标,考察了萃取头、萃取时间、离子强度、萃取温度对酱油样品中挥发性风味物质萃取的影响。该方法对酱油中常见挥发性风味成分的测定有良好的重复性和回收率,对常见挥发性物质的定量比较准确。优化的HS-SPME条件为：涂层厚度为85 μm聚丙烯酸酯(PA)萃取纤维头,于45 ℃、NaCl质量浓度为250 g/L下对酱油样品顶空吸附40 min,于250 ℃下解吸2 min后进行GC-MS分离鉴定。酱油样品的分析结果表明,其挥发性风味物质中含量较高的是醇、酸、酯和酚类,此外还有一些羰基化合物和杂环化合物。     

顶空固相微萃取-气相色谱质谱法定性定量分析广藿香中的挥发性成分

采用顶空固相微萃取-气相色谱质谱法(HS-SPME/GC-MS)定性定量分析广藿香药材中的挥发性成分.以百秋里醇的峰面积为指标,确定HS-SPME最佳的实验条件为:160目药材粉末用无水 Na2SO4稀释10倍,称取30 mg于15 mL萃取瓶中,以250 r/min速度搅拌预热(80 ℃) 40 min,插入65 μm聚二甲基硅烷-二乙烯(PDMS-DVB)涂层的纤维头,在相同搅拌速度下80 ℃萃取40 min,纤维头进入GC进样口在250 ℃下解吸100 s.GC色谱条件:色谱柱为DB-5MS柱;载气流速为1 mL/min;柱温的起始温度为90 ℃,以0.8 ℃/min升至110 ℃,保持5 min;1.0 ℃/min升至134 ℃,保持5 min;最后以5.0 ℃/min升至143 ℃,保持10 min.结果:百秋里醇的平均回收率为91.8%,RSD为3.0%.运用本方法对10份不同产地广藿香中百秋里醇的含量进行测定,并以其为参比对照,测定了广藿香中其它主要挥发性成分的含量.     

顶空固相微萃取-气相色谱-质谱联用快速分析八角茴香中风味物质

采用顶空固相微萃取与气相色谱-质谱联用技术,对八角茴香中风味物质进行了分析。选用自制聚丙烯酸树脂涂层,对样品量、萃取时间、萃取温度、解吸时间等参数进行了优化,结果表明0．10g样品在60℃水浴中顶空萃取40min,250℃下解吸2min达到最佳条件。比较了顶空固相微萃取与传统水蒸气蒸馏两种前处理方法,分析结果非常相似。该方法可用于快速分析八角茴香中的风味物质。     

顶空液液萃取-气相色谱-质谱法用于白术挥发性成分的分析

采用高温顶空液相萃取再转移的方法,对中药白术中挥发性成分进行萃取分离富集,采用顶空液液萃取/气相色谱-质谱(HS-LP-LPE/GC-MS)联用法进行测定,并与传统水蒸汽蒸馏法(SD)提取的挥发性成分进行对比。对各种测定条件和影响因素进行了考察,最佳萃取条件为:1.0 mL PEG 400为高温萃取剂,样品用量1.2 g,萃取温度120℃,萃取时间60 min,再将萃取剂用1.0 mL正己烷进行反萃取后进行GC-MS分析;采用HS-LP-LPE/GC-MS鉴定了33个组分,占总组分含量93.18%;SD鉴定了31个组分,占总组分含量97.12%。两种方法共同检测到的组分有29个,均以苍术酮(Atractylone)含量最高。结果表明,两种方法所提取的组分基本相同,可用于白术挥发性成分的测定。     

顶空固相微萃取-气质联用分析小麦储藏过程中挥发性成分变化

采用顶空固相微萃取(HS-SPME)和气相色谱-质谱联用(GC-MS)对不同储藏时间弱(强)筋小麦中的挥发性物质进行提取、鉴定与分析.选用复合萃取纤维二乙烯基苯-炭烯-聚二甲硅氧烷共聚物(DVB/CAR/PDMS)50 μm涂层,对萃取温度、时间、样品用量和解析时间进行优化.结果表明: HS-SPME测定挥发性物质的最佳前处理条件样品量20 g, 萃取温度75 ℃, 萃取时间60 min, 260 ℃条件下解析5 min;经鉴定分析小麦挥发性成分主要有烃类、醛类,其次为醇类、酮类;挥发性成分总含量在储藏6个月内均呈现先降后增的趋势.弱筋小麦的烃类挥发物相对量随储藏时间延长而快速增加,醛类相对含量先降后升,而酮类和醇类相对含量则逐渐下降;强筋小麦中除烃类相对含量呈先下降而后快速增加外,其余各类挥发物含量均与弱筋小麦呈现相同的规律.储藏6个月后,变化较明显的挥发性物质有己醇、己醛、2,6,10-三甲基-十二烷、十五烷和二十烷.     

顶空-固相微萃取法与水蒸气蒸馏法提取沙棘挥发油组分的比较研究

优化了顶空-固相微萃取法(HS-SPME)提取沙棘挥发性成分的条件,并采用气相色谱-质谱联用技术(GC-MS)分别对HS-SPME法和水蒸气蒸馏法(SD)的提取物进行分析。结果显示,在萃取温度为70℃,萃取时间为50 min,解吸时间为7 min,平衡时间为20 min条件下,HS-SPME法鉴定出76种组分,占挥发性物质总量的90.19%,主要成分为酯类、醛类和酮类;而SD法提取物共鉴定出56种组分,占挥发性物质总量的91.98%,主要成分为酯类。2种方法共有组分为20种。两种方法提取的沙棘挥发油组分的种类及含量差异较大,HS-SPME法更适合沙棘挥发性组分的快速检测。     

顶空固相微萃取-气相色谱-质谱法用于白术中挥发性成分的分析

采用顶空固相微萃取-气相色谱-质谱法(HS-SPME-GC-MS)分离鉴定了白术中的挥发性成分,并与采用传统的水蒸气蒸馏法(SD)提取的挥发性成分进行了比较。实验中筛选了固相微萃取纤维头,优化了SPME的操作条件。样品在70 ℃下平衡30 min后,用65 μm聚二甲基硅氧烷-二乙烯基苯(PDMS-DVB)纤维头对白术样品顶空吸附30 min,于250 ℃下解吸4 min, 然后采用GC-MS对解吸物进行分离鉴定;采用HS-SPME-GC-MS鉴定出41种组分,占总峰面积的90.81%;采用SD-GC-MS鉴定出31个组分,占总峰面积的88.19%,且采用SD所提取的组分基本上都被固相微萃取所提取。结果表明, HS-SPME可取代耗时的SD用于白术中挥发性物质的提取。     

顶空-固相微萃取-气相色谱-质谱法测定烟气中挥发性和半挥发性成分

提出了顶空-固相微萃取-气相色谱-质谱法测定烟气中挥发性和半挥发性成分。结合信息量最大的原则,确定了固相微萃取时萃取纤维头为碳分子筛/聚二甲基硅烷萃取纤维头,萃取温度为70℃,萃取时间为60min。在气相色谱分离中用Agilent DB-1色谱柱为固定相,在质谱分析中采用全扫描模式。结果表明:共鉴定出107种成分,含量最大的成分是烟碱(18.07%),其次是新植二烯(11.46%),主要的3类挥发性和半挥发性成分依次为苯系物、酮类以及杂环类。     

顶空固相微萃取-气质联用技术分析5种荷花的挥发性成分

采用顶空固相微萃取-气相色谱质谱联用(HS-SPME-GC-MS)技术分析测定了5个品种荷花中的挥发性成分.考察了不同萃取头和萃取温度对荷花挥发性成分萃取的影响,选用65μm PDMS/DVB SPME萃取头和25℃室温萃取荷花中的挥发性成分得到较好的萃取效果.应用峰面积归一化法测定各挥发性成分的相对含量,5个品种共鉴...     

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.     

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%).     

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.     

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.     

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.