顶空固相微萃取/气相色谱-质谱联用测定水中6种挥发性硅氧烷

建立了水中4种环形和2种线形硅氧烷的顶空固相微萃取/气相色谱-质谱联用分析方法.考察了萃取纤维、萃取温度、萃取时间、水样pH值、解析时间、盐效应等因素对实验结果的影响.优化后的条件为:40mL水、40 μL内标(M4Q,500 μg/L)、NaCl(0.1 g/mL)加入60 mL顶空瓶中,选用65μm聚二甲基硅氧烷-二乙烯基苯(PDMS/DVB)纤维于24℃顶空萃取45 min.萃取完成后将纤维插入气相色谱进样口,于200℃解吸2 min进行定性、定量分析.结果表明,6种目标物的方法检出限为(LOD)2.6～7.8 ng/L,回收率为82％～ 96％,相对标准偏差(RSD)为1.1％～7.9％.     

活性炭固相微萃取-气相色谱联用测定海水中酞酸酯

利用自制的活性炭纤维结合固相微萃取-气相色谱联用技术(ACF-SPME-GC)分析了海水中4种邻苯二甲酸酯.对萃取温度、离子强度、吸附和热解吸时间等影响因素进行了研究.结果表明,在盐浓度为15%和萃取温度为60 ℃条件下萃取60 min,效果最好.在最优化条件下,本方法的线性范围为0.1～1000 μg/L; 检出限为0.01～10 μg/L; 相对标准偏差均小于10%.将ACF-SPME-GC技术用于实际海水样品的分析,未检测出这4种邻苯二甲酸酯化合物.     

环境水样中己烯雌酚与双烯雌酚的离子液体分散液-液微萃取/高效液相色谱法测定

以离子液体([Omim][PF6])为萃取剂,采用冷诱导分散液-液微萃取对环境水样中的己烯雌酚和双烯雌酚残留进行富集.优化后的萃取条件:在pH 3.0的条件下,以50 μL离子液体为萃取剂,0.8 mL甲醇为分散剂,采用反相 Extend-C18柱(5 μm, 250 mm×4.6 mm),流动相为水-甲醇(体积比40 ∶ 60),流速:1.0 mL/min,柱温:35 ℃,检测波长:245 nm.在优化的萃取条件下,己烯雌酚和双烯雌酚的线性范围均为2.5 ～200 μg/L,检出限(S/N=3)为80 ng/L.应用于环境水样中己烯雌酚和双烯雌酚的检测,加标回收率为93% ～98%,相对标准偏差为3.0% ～5.4%,建立的方法简单、环保.     

气相色谱-质谱法测定包装材料中全氟辛酸及其盐类

快速溶剂萃取法萃取包装材料中的全氟辛酸(PFOA)及其盐类, 萃取液与乙酰化试剂反应后, 以全氟癸酸甲酯为内标物, 用内标法进行定量测定. 气相色谱质谱条件为: HP-Innowax毛细柱;柱温: 50 ℃ (5 min)30 ℃/min→240 ℃ (5 min);不分流进样;接口温度: 280 ℃;载气: 氦气, 0.8 mL/min;进样量: 1 μL;负化学源;反应气: 甲烷, 20%;选择离子扫描方式. 方法的线性范围1.0～105 μg/L, 线性相关系数r=0.999, 检出限0.1 μg/L, 不同浓度的PFOA的相对标准偏差分别为4.1%和3.2%, 回收率在87%～109%之间.     

离子液体顶空单滴微萃取分析中药中的高沸点挥发性成分

建立了分析中药中高沸点挥发性成分的离子液体顶空单滴微萃取-液相色谱法,并用于复方鲜竹沥液中愈创木酚的含量的测定.采用改进的悬滴装置,增大了液滴与微量进样器针尖处塑料套管的接触面积,使离子液体的液滴达12 μL,提高了液滴的稳定性及方法的灵敏度.考察并优化了影响萃取的因素,确定了萃取条件:以12 μL 1-丁基-3-甲基咪唑基六氟磷酸盐([PF6])为悬滴,在5 mL含36%(w/V)NaCl的样品溶液中,萃取温度80 ℃、搅拌速度1000 r/min的条件下,顶空萃取30 min,萃取后直接将液滴吸回微量进样器,进行HPLC检测.愈创木酚在0.05～1.6 mg/L范围内线性关系良好(r=0.9997); 检出限为0.39 μg/L,愈创木酚的加样回收率为97.6%,RSD为2.5%.本方法操作简单、定量准确,样品前处理简单,成本低,无污染.     

聚吡咯-离子液体固相微萃取涂层的电沉积制备及其在苯类化合物气相色谱检测中的应用

在0.1 mol/L吡咯-0.1 mol/L对甲苯磺酸-4g/L 1-丁基-3-甲基咪唑四氟硼酸盐水溶液中,通过循环伏安法在不锈钢丝表面制备了新型聚吡咯-离子液体(Polypyrrole-ionic liquid,PPY-IL)涂层.此涂层呈菜花状结构,粒度比PPY小.以5种苯类化合物(即1,2-二甲苯、1,2,4-三氯苯、1,2-二氯苯、1,2,4-三甲苯和1,3,5-三甲苯)为目标分析物,对所得萃取头性能进行了考察.在优化的实验条件(萃取温度:50℃；萃取时间:40 min;搅拌速率:600 r/min; NaCl浓度:0.2 g/mL)下,对这些苯类化合物进行顶空固相微萃取-气相色谱检测,其线性范围为0.6～800 μg/L,单根多次萃取的相对标准偏差小于4.5％(n=5),多根萃取头平行萃取的相对标准偏差为4.5％～12.4％(n=5).PPY-IL萃取头有良好的稳定性,在使用150次后萃取性能仅有很小的变化；在温度升至290℃时不分解.与聚吡咯和聚二甲基硅氧烷萃取头相比,本萃取头对这些苯类化合物有更高的萃取能力.     

环境水样中百菌清残留的单滴微萃取-反相液相色谱测定

应用单滴微萃取(SDME)-反相液相色谱(RPLC)检测了环境水样中的百菌清残留.优化了单滴微萃取条件:环己烷萃取剂6 μL、单滴体积2 μL、搅拌速率350 r/min、萃取时间40 min、水溶液温度35 ℃、无盐度.水样经单滴微萃取后,使用Hypersil C18柱反相液相色谱分离测定百菌清.反相液相色谱条件:100%甲醇流动相、流速1.0 mL/min、柱温25 ℃、224 nm检测.方法的线性范围、检出限、相对标准偏差和富集倍数分别为1.0 ～50 μg/L、0.02 μg/L、6.1%和427倍.采用该法对环境水样中的百菌清残留进行了测定,环境水样的加标回收率为98% ～106%.     

液相微萃取/离子色谱测定牛奶中的氨

以水为微滴萃取溶剂,采用顶空液相微萃取/离子色谱检测了牛奶中的氨.优化了顶空液相微萃取的实验条件:pH=12,萃取温度为35 ℃,萃取时间为15 min,搅拌速率为800 r/min,萃取溶剂体积为5 μL.测定氨的线性范围为10 ～300 μg·L-1(R2=0.998),检出限达1.8 μg·L-1,回收率为92% ～105%.     

超声辅助离子液体分散液相微萃取-高效液相色谱法测定废水中雌激素的研究

将离子液体、分散液相微萃取与超声萃取技术结合,采用疏水性离子液体1-丁基-3-甲基咪唑六氟磷酸盐([C4 MIM][PF6])为萃取剂,建立了超声辅助离子液体分散液相微萃取-高效液相色谱法分析废水中3种雌激素物质(己烯雌酚、双烯雌酚、己烷雌酚)方法.试验采用50μL的离子液体,考察了溶液体积、溶液pH值、超声时间、静置时间、离心时间等因素对富集效果的影响.最佳的萃取条件为:溶液体积为6 mL,甲醇体积0.3 mL,溶液pH值为2.0,超声时间6min,静置时间30min,离心时间10 min.在优化的萃取条件下,3种雌激素的富集倍数可达到96.8～112.4倍;方法的线性范围为0.5-100.0μg/L;检出限为0.25～0.50μ/L.对浓度为5.0μg/L的3种物质测定6次的相对标准偏差为9.2%～10.8%.     

原位衍生分散液相微萃取-气相色谱/质谱快速检测饮用水中的痕量三氯生

建立了原位衍生分散液相微萃取-气相色谱/质谱检测饮用水中痕量三氯生的方法.将含有30.0 μL氯苯(萃取剂)和50.0 μL乙酸酐(衍生试剂)的0.5 mL丙酮(分散剂)作为萃取体系,快速注入到5.0 mL含有K2CO3(0.5%, m/V)的水溶液中.在5000 r/min下离心2 min后,得到(10±0.5) μL沉积相(氯苯),取底部沉积相1.0 μL进行气相色谱/质谱联用仪分析.方法的线性范围为0.05～50 μg/L(r=0.9994),检出限为0.01 μg/L;相对标准偏差2.0%(n=5).利用本方法检测了饮用水中的三氯生,平均加标回收率分别为92.1%和98.4%,结果满意.     

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.     

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.     

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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.