啤酒风味物质及游离脂肪酸的气相色谱研究

啤酒中含量极低、极不稳定的游离脂肪酸(FFAs)是影响啤酒风味的主要因素。实验采用气相色谱技术,对形成啤酒的主要风味(如药物味、水果味、酒精味和哈喇味等),重点是不良风味的风味物质进行了检测。啤酒样品经两次酸化处理,酯化后薄层分离的方法测得游离脂肪酸的含量具有较好的重复性和较高的回收率,以癸酸和亚油酸为代表测得回收率分别为85%和114%。     

气相色谱法测定面包中三种单甘油酯含量

建立了气相色谱法检测面包中3种单甘油酯(单辛酸甘油酯、单癸酸甘油酯和单月桂酸甘油脂)含量的分析方法。样品以二氯甲烷-正己烷(1∶1)提取,提取液经浓缩后,用正己烷饱和乙腈萃取,气相色谱测定,外标法定量。3种单甘油酯在20～1 000 mg/L范围内呈良好线性,相关系数(r)大于0.999。3种单甘油酯的定量下限分别为35.2、23.3、12.8 mg/kg,加标回收率为81.1%～95.7%,相对标准偏差(RSD)为2.9%～8.8%。该法操作简便、灵敏度高、重现性和选择性好,可用于面包中3种单甘油酯的检测。     

气相色谱-质谱法测定染整助剂中19种有害有机溶剂

建立了同时测定染整助剂中19种有害有机溶剂残留量的气相色谱-质谱方法。以甲醇为萃取溶剂,样品经常温超声萃取后,萃取液直接进气相色谱-质谱联用仪进行定性定量分析。19种有机溶剂在0.5~50.0 mg/L范围内线性关系良好,相关系数不小于0.999,检出限为0.03~0.10 mg/kg,加标回收率为94.3%~101.3%,相对标准偏差均小于8.7%(n=10),符合残留分析的技术指标要求。该方法准确、稳定,可测定染整助剂中有害有机溶剂的残留量。     

农产品中6种有机溶剂残留的气相色谱-质谱检测方法

建立了蔬菜、粮食等农产品中6种有机溶剂残留(甲苯、邻二甲苯、间二甲苯、对二甲苯、N,N-二甲基甲酰胺(DMF)和二甲基亚砜(DMSO)的液液萃取/气相色谱-质谱分析方法。不同类型的样品经乙腈-水溶液或乙腈溶剂提取后,用Agilent DB-624(30.0 m×250μm×1.4μm)毛细管色谱柱分离,在GC-MS选择离子监测(SIM)模式下检测,以保留时间和特征离子丰度比定性,外标法定量。结果表明,该方法对不同样品中4种苯系物在0.005~0.500 mg/L,DMF在0.025~0.125 mg/L,DMSO在0.050~0.500 mg/L浓度范围内线性关系良好,相关系数(r)为0.992 0~0.997 1。6种有机溶剂的平均加标回收率为60.1%~115.2%,相对标准偏差不大于11.0%。苯系物、DMF和DMSO的方法检出限(S/N=3)分别为0.002~0.050,0.010~0.025,0.060~0.150 mg/kg。该方法准确、快速、灵敏,可用于各种农产品中有机溶剂残留的监控。     

椰子油甘油三酯的高温气相色谱/质谱分析

以HP 5MS毛细管柱 30m× 0 .2 5mm× 0 .2 5 μm分离椰子油中各甘油三酯 ,通过各自EI质谱确定其组成。进样量 1μL(以 10g L溶于正己烷 ) ,分流比为 1∶5 0 ,温度程序为 :柱温 30 0℃ ,保持 3min ,以 2℃ min速率升至 35 0℃ ,保持 12min。扫描范围m z 30～ 80 0amu。共鉴定出 36种甘油三酯。其中以辛酸双月桂酸甘油酯 (12 .4 8% ,峰面积百分比 ,下同 ) ,癸酸双月桂酸甘油酯 (7.6 9% ) ,辛酸月桂酸肉豆蔻酸甘油酯 (10 .81% ) ,三月桂酸甘油酯和癸酸月桂酸肉豆蔻酸甘油酯 (15 .34% ) ,双月桂酸肉豆蔻酸甘油酯和癸酸月桂酸棕榈酸甘油酯 (17.0 1% ) ,双月桂酸棕榈酸甘油酯和癸酸月桂酸硬脂酸甘油酯 (11.0 9% )为主。     

微波辅助萃取/气相色谱-质谱联用法同时测定皮革及其制品中12种乙二醇醚类有机溶剂残留量

以甲醇为溶剂,85℃下微波萃取皮革及其制品中的乙二醇醚类有机溶剂,萃取物经固相萃取柱净化后进行气相色谱-质谱/选择离子监测法测定,外标法定量,从而建立了同时测定皮革及其制品中12种乙二醇醚类有机溶剂残留量的气相色谱-质谱联用方法。该方法的加标回收率为81.1%~95.9%,相对标准偏差(RSD,n=9)为1.4%~9.6%。在信噪比(S/N)为10的条件下,各组分的定量下限(LOQ)为0.05~0.20mg/kg。该方法操作简单、方便快速、灵敏度高,可满足皮革及其制品中乙二醇醚类有机溶剂残留量检测的技术要求,并为制定相关检测标准提供了参考。     

固相微萃取-高效液相色谱-荧光检测法测定番茄中的多菌灵和噻菌灵

建立了应用固相微萃取(SPME)-高效液相色谱(HPLC)-荧光检测法测定番茄中多菌灵(MBC)和噻菌灵(TBZ)的分析方法。考察了萃取纤维、萃取时间、萃取温度、解吸时间、解吸液组成、解吸模式、pH值、有机溶剂和离子强度对MBC和TBZ萃取效率的影响,对SPME条件和色谱条件进行了优化。SPME在室温下进行,采用65 μm聚二甲基硅氧烷/二乙烯苯（PDMS/DVB）萃取纤维,萃取溶液中加入100 g/L NaCl,搅拌速度为1100 r/min,萃取时间为50 min。将该法用于番茄中MBC和TBZ的测定,MBC和TBZ的定量线性范围均为0.01~1.0 mg/kg;线性相关系数分别为0.9958和0.9967;检出限分别为0.003和0.001 mg/kg;回收率分别为83.5%和85.6%(n=5),相对标准偏差(RSDs)分别为6.5%和3.8%。该方法操作简单,无需使用有机溶剂,适于分析番茄样品中的MBC和TBZ。     

气泡微萃取-气相色谱-质谱法测定尿中咖啡因

建立了气泡微萃取结合气相色谱/质谱技术(GC-MS)测定尿中咖啡因的方法.对影响萃取效率的实验条件进行了优化,确定了最佳萃取条件:三氯甲烷作为萃取溶剂,萃取溶剂暴露体积1 μL,气泡体积1.6 μL,搅拌速度300 r/min,萃取时间5 min,盐度15%(m/V),气泡与磁子间距离1 cm.在优化条件下,所建立方法在咖啡因浓度0.005~10 mg/L范围内有较好的线性关系,相关系数可达0.986,检出限为0.003 mg/L.在人尿液中添加不同浓度的咖啡因(0.050、0.500和5.000 mg/L),回收率为89.2%~107.5%,相对标准偏差小于8%(n=6).     

气相色谱-质谱法测定尿中有机磷代谢产物

建立了测定尿中有机磷农药代谢产物-二烷基磷酸酯(DAPs)类化合物的气相色谱-质谱(GC-MS)分析方法。样品经乙腈-乙醚(1:1,V/V)萃取,五氟溴苄苯衍生,再由正己烷提取衍生物,固相萃取净化,气相色谱-质谱(GCM S)结合选择离子监测模式(SIM)定性,内标法定量。各种二烷基磷酸酯的衍生物在0.05~10 mg/L范围内线性关系良好,相关系数r≥0.993;平均回收率为51.6%~90.8%,相对标准偏差(n=6)小于29%;方法检出限为0.001~0.002 mg/L。     

液相微萃取-气相色谱法测定尿液中氨基比林、安替比林和巴比妥的研究

建立了一种以液相微萃取(Liquid Phase Microextraction,LPME)与气相色谱-氢火焰(LPME-GC-FID)联用技术为基础的测定尿样中氨基比林、安替比林和巴比妥的方法。考察了萃取溶剂、萃取时间、pH对萃取效果的影响。氨基比林、安替比林、巴比妥线性范围分别为1.67~333、133~667、60~300 mg/L,检出限分别为1、4、12 mg/L。     

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%.     

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.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.