采用溶胶-凝胶技术涂层的新型固相微萃取方法及其应用

将溶胶-凝胶技术应用于SPME固相涂层的制备,涂制的端羟基-聚二甲基硅氧烷固相涂层热稳定性好,萃取时间和解吸时间短,对极性化合物及非极性化合物均有较强的萃取富集能力。扫描电镜图显示涂层表面为多孔结构。采用该涂层的SPME方法在对环境样品的分析中获得了令人满意的效果。     

固相微萃取/气相色谱-质谱联用技术测定燕窝中挥发性成分

该文以印尼产的燕窝为材料,使用固相微萃取(SPME)技术萃取燕窝中挥发性成分并以气相色谱-质谱(GC-MS)联用仪进行测定。考察了萃取头类型、萃取温度、萃取时间和解吸时间对固相微萃取(SPME)在燕窝挥发性成分测定中的影响。结果表明:以65μm聚二甲基硅氧烷/二乙烯基苯(PDMS/DVB)萃取头、在60℃下萃取60 min,解吸2 min的条件下,SPME/GC-MS技术可检出燕窝中挥发性成分醇、烃、醛、酯、醚类等化合物共82种。该方法具有操作简便、快速、重复性好和灵敏度高的特点,适用于燕窝中挥发性成分的测定。     

固相微萃取-气相色谱法测定食品添加剂中有害有机挥发杂质

建立了固相微萃取（SPME）-气相色谱法（GC）测定食品添加剂中有害有机挥发杂质：二氯甲烷、三氯甲烷、苯、三氯乙烯和1、4-二n恶烷的方法。以聚二甲基硅氧烷（PDMS）涂层的萃取纤维萃取糖精钠、柠檬酸、苯甲酸钠溶液中的待测组分。以HP-5毛细管柱为分离柱，火焰离子化检测器（FID）定量测定。优化了固相微萃取条件：萃取纤维、萃取方式、萃取温度、平衡时间、pH及电解质浓度等。在优化的试验条件下，进行了方法的检出限、精密度、回收率试验。5种组分的回收率在97．3％～103．9％之间。     

固相微萃取―气相色谱―质谱联用方法分析人参中的挥发性物质

采用固相微萃取―气相色谱―质谱联用(SPME-GC-MS)的方法测定了人参中的挥发性物质,并对萃取头类型、萃取温度、萃取时间进行了优化。结果表明,当采用100μm聚二甲基硅氧烷(PDMS)的萃取头(非极性),80℃萃取30 min时,萃取效果最好。结果显示,人参中主要的挥发性物质为γ-榄香烯和β-古芸烯等。     

顶空固相微萃取-气相色谱-质谱联用分析纺织品中挥发性有机物

建立了顶空固相微萃取（HSSPME）-气相色谱（GC）-质谱（MS）联用测定纺织品中甲苯、4-乙烯基环己烯、苯乙烯、萘和1-苯基环己烯5种挥发性有机物（VOCs）的分析方法。选择聚二甲基硅氧烷（PDMS）作为萃取涂层,优化了SPME的萃取条件,包括平衡时间、萃取时间、萃取温度、顶空体积、离子强度、搅拌速度、解吸温度和时间以及GC—MS仪器条件。对于甲苯、4-乙烯基环己烯、苯乙烯、萘和1-苯基环己烯方法线性范围分别为0．087～870、3．32～3320、2．28～2280、0．015～150和0．050～50．0ng／g;检出限分别为0．005、0．042、0．670、0．008和0．011ng／g。实际样品加标回收率在80．1％～122％之间,RSD在0．8％～8．6％之间。方法符合纺织品中痕量VOCs的快速分析要求。     

苯丙共聚物-聚硅氧烷复合固相微萃取涂层的制备及性能研究

合成了苯乙烯-丙烯酸乙酯共聚物,以此聚合物与甲基聚硅氧烷色谱固定液混合作为固相微萃取头涂层。通过热分析手段考察了该涂层的热稳定性,涂层使用温度可达280℃。使用微量进样器和不锈钢毛细管,自制了SPME装置。使用该涂层萃取分析了水中氯苯系化合物,各标准样品质量浓度在0—20μg／L内与色谱峰面积呈良好线性关系（r=0．9674—0．9934）,检出限为0．28—0．64ng／L,相对标准偏差为5．4％-7．7％,加标回收率为91％-99％。将自制涂层与商品涂层（PDMS、PA）进行了比较,结果表明苯丙聚合物-甲基聚硅氧烷复合涂层对氯苯系化合物具有优良的吸附特性。在固相微萃取研究和应用中,提供了新的吸附物质和色谱固定液与石英纤维结合的新途径。     

葫芦脲用作固相微萃取涂层新材料

本文对葫芦脲(CB)作为一种新型固相微萃取(SPME)涂层材料进行了研究并用于中药白豆蔻的气相色谱分析测定.本文采用的CB SPME涂层制备方法简便、快速,并具有良好的热稳定性和重复性.CB[6]SPME萃取得到的主要成分与水蒸气蒸馏（SD）法基本一致,并且CB[6]SPME对色谱后流出的目标成分的相对峰面积比明显高于SD法和商品SPME萃取材料PDMS/CAR和PDMS/DVB,这可能是由于葫芦脲的特殊分子结构及其与组分分子间选择性作用所致.葫芦脲作为一种新型SPME涂层材料具有很大的研究潜力和应用前景.     

聚苯乙烯-丙烯酸乙酯新型固相微萃取吸附质的研究与应用

固相微萃取(SPME)是90年代兴起的新型无溶剂样品前处理技术,基本的固相微萃取是通过石英纤维头表面涂渍的高分子层对样品中的有机分子进行萃取和预富集,然后进行色谱分析,使预处理过程大为简化,提高了分析速度及灵敏度。目前,商品SPME．GC联用装置是由美国Supclco公司生产的涂有PDMS、PA、PEG20M3种单一吸附质及4种部分交联的复合固相材料。涂层极性决定了其应用范围。     

固相微萃取新型活性炭涂层萃取头的研究

利用合成的有机硅树脂胶粘剂和活性炭微粉首次制成活性涂层萃取头。通过苯系物(BTEX)表征了涂层表观结构、厚度及萃取性能。对苯、甲苯、乙苯、对二甲苯、邻二甲苯等进行固相微萃取,结果表明:该萃取头热稳定性好,最高使用温度可达290℃;使用寿命长,250℃解吸条件下反复使用140余次以后,膜层没有脱落或性能下降的现象。该涂层对苯系物的最低检出质量浓度在0 21～0 94μg L之间。与100μm的商品聚二甲基硅氧烷(PDMS)涂层相比,对苯系物的富集能力整体上相当。     

固相微萃取-气相色谱联用技术测定柠檬酸中的有机挥发性杂质

利用顶空固相微萃取．气相色谱联用技术(HS-SPME-GC)，以100μm聚二甲基硅氧烷(PDMS)萃取头分析柠檬酸中的5种有机挥发性杂质，并对萃取温度、吸附时间、解吸时间和盐析作用进行了研究。结果显示，该方法具有较好的精密度和较宽的线性范围，样品加标回收率92．4％-103．5％，检出限完全满足美国药典USP23对柠檬酸中有机挥发性杂质的限量要求。     

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.     

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.