吹扫捕集-气相色谱联用测定城市河流中的挥发性硫化物

建立了一种吹扫捕集 气相色谱联用测定城市河流中挥发性硫化物的方法。二甲基硫、甲基乙基硫、二甲基二硫最低检测质量浓度分别为80,80和100ng/L,水样加标回收率在91%～101%之间。方法操作简单,灵敏度高,成功应用于城市河流中水样中挥发性硫化物的测定。     

超声提取辅助顶空式固相微萃取/气相色谱-质谱法测定塑胶跑道面层中7种挥发性硫化物

建立了一种检测塑胶跑道面层中二甲基硫(DMS)、二硫化碳(CS2)、甲基乙基硫(MES)、二乙基硫(DES)、二甲基二硫(DMDS)、二乙基二硫(DEDS)、二甲基三硫(DMTS)7种挥发性硫化物(VSCs)的超声提取辅助顶空式固相微萃取/气相色谱-质谱(HS-SPME/GC-MS)分析方法.实验优化了顶空固相微萃取的...     

顶空固相微萃取气相色谱-火焰光度法测定废水中烷基硫醇化合物

建立了顶空固相微萃取(HS-SPME)-气相色谱法测定人工湿地废水中烷基硫醇化合物的分析方法.详细研究了萃取参数如萃取涂层、萃取时间、萃取温度、样品体积、盐效应及样品pH值等对HS-SPME萃取乙硫醇(EtSH)、2-甲基-2-丙硫醇(Me-PrSH)、1-丙硫醇(1-PrSH)、2-丙硫醇(2-PrSH)、1-丁硫醇(1-BuSH)及环戊硫醇(CycloPeSH)(内标)的影响.富集的硫醇化合物经DB-VRX毛细管色谱柱分离,FPD检测.在优化的实验条件下,测定乙硫醇、2-甲基-2-丙硫醇、1-丙硫醇、2-丙硫醇、1-丁硫醇的线性范围介于0.12～16.21 μg/L之间; 检出限(3σ)介于0.97～22.11 ng/L之间.以环戊硫醇为内标物质,将本法用于废水中硫醇化合物的测定,获得满意结果.     

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.     

HS-SPME–GC–MS法测定水中2-甲基异冰片及土臭素

采用顶空固相微萃取–气质联用(HS-SPME–GC–MS)的方法对地表水中2-甲基异冰片(2-MIB)和土臭素(GSM)进行分析测定。通过试验确定了HS-SPME的最佳萃取条件:萃取头为DVB/CAR/PDMS,萃取时间为30 min,萃取温度为70℃,NaCl的加入量为30%(质量分数),萃取纤维在GC上的解吸温度为250℃。用内标法进行定量,2-MIB,GSM的质量浓度在5~100 ng/L范围内与色谱峰面积呈良好的线性关系,线性相关系数(r2)分别为0.999 7,0.997 0,检出限分别为0.8,1.7 ng/L。采用该法对水样进行测定,2-MIB,GSM测定结果的相对标准偏差为2.6%~6.3%(n=6),加标回收率为92%~112%。该方法能简单、快速地测定水中痕量嗅味物质。     

海水和大气中挥发性硫化物分析方法的研究

建立了大气和海水中挥发性硫化物的气相色谱分析方法,确定了最佳实验条件.为了适应不同的基质和保存方式,大气和海水样品采用了不同的分析方法.测定大气样品时,采用大气采样罐及三级冷阱预浓缩气相色谱-质谱联用技术,而海水样品采用吹扫捕集-气相色谱测定.本方法测定大气挥发性硫化物的线性范围较好,精密度为7.7%~15.1%,检出限为0.23~4.7 ng;海水中挥发性硫化物的精密度为3.5%~5.3%,检出限为2.5~3.5 ng.将本方法用于青岛近海海水和大气中硫化物的测定,测得海水中羰基硫、二甲基硫和二硫化碳的平均浓度分别为(268±58)pmol/L、(1264±0.2)pmol/L、(19±2)pmol/L,大气中的平均浓度为543±39、39±9和56±20(×10-12,V/V).本方法可准确测定海洋环境中的挥发性硫化物.     

顶空固相微萃取/气相色谱-三重四极杆串联质谱法测定地表水与饮用水中的挥发性有机物

采用部分因子试验设计筛选出顶空固相微萃取的主要影响参数,利用中心复合设计对主要影响参数的取值进行了优化,建立了顶空固相微萃取(HS-SPME)结合气相色谱-三重四极杆串联质谱(GC-MS/MS)测定地表水和饮用水中55种挥发性有机物(VOCs)的分析方法。取5.0 mL样品于顶空瓶中,加入0.75 g NaCl,使用CAR/PDMS 75μm纤维头,萃取温度40℃,萃取时间40 min,解析温度300℃,在GC-MS/MS选择反应监测(SRM)模式下检测,内标法定量。结果表明,55种VOCs在0.04～0.40、0.4～4.0、4.0～100μg/L质量浓度范围内线性良好,相关系数(r~2)均大于0.99,方法的检出限为0.03～80 ng/L,定量下限为0.1～300 ng/L。55种VOCs在0.2、2.0、40μg/L 3个加标水平下的平均回收率为77.3%～124%,相对标准偏差(RSD,n=6)为1.3%～17%。对3种地表水和3种饮用水进行测定,地表水中有37种VOCs被检出,饮用水中有25种VOCs被检出。实验证明,建立的HS-SPME和GC-MS/MS相结合的检测方法具有准确可靠、简单快速、灵敏度高等优点,适用于地表水和饮用水中VOCs的同时测定。     

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。     

微萃取瓶富集-高效液相色谱法测定海水中多环芳烃

采用自制微萃取瓶富集-反相高效液相色谱法同时测定海水中的萘、菲、荧蒽。实验选择DiamonsilC18(250×4.6mmi.d.,5μm)色谱柱,体积比为88∶12的甲醇-水作流动相,流速1.0mL/min,检测波长280nm,柱温30℃。最佳萃取条件:400mL水样,300μL正辛烷作萃取剂,NaCl浓度100g/L,萃取时间15min。在10～5×104μg/L范围内,萘、菲、荧蒽呈现良好线性关系(相关系数均大于0.9997)。萘、菲、荧蒽检出限分别为13.3、13.3、7.0ng/L;加标回收率分别为94.50%、94.05%、92.59%;相对标准偏差分别为1.60%、1.82%、0.90%。     

气相色谱-质谱法及嗅探技术分析蓝藻水华水体中挥发性成分

采用顶空固相微萃取富集蓝藻水华水中挥发性成分,用气相色谱-质谱联用进行定性分析,对色谱峰峰面积进行归一化,计算出各成分相对百分含量,比较了不同萃取涂层、萃取温度及采样时间对分析结果的影响.确定了固相微萃取的最佳条件:CAR/PDMS涂层,萃取温度45℃,采样时间25 min.鉴定出丁酸、异戊酸、乙酸、二甲基三硫、己酸、邻甲酚、丙酸、二甲基二硫、正戊酸、β-柠檬醛、硫代丁酸甲酯、3-甲基吲哚、异戊醇、甲硫醇、1-丁醇等82种化学成分.采用质谱检测器与嗅探分析器并联方式,有效鉴别得到引起人体嗅觉反感的蓝藻水华主要异味物质18种,其中二甲基三硫、二甲基二硫及β-柠檬醛为蓝藻水华暴发后增加最明显的恶臭物质.     

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.     

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.     

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.     

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.     

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.     

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.