毛细管离子色谱-串联质谱法测定热纤梭杆菌发酵液中的低相对分子质量有机酸

建立了一种测定热纤梭杆菌发酵液中的低相对分子质量有机酸的毛细管离子色谱-串联质谱方法。探索优化了色谱和质谱的检测条件,在最佳分析条件下同时检测8种有机酸。离子色谱以KOH水溶液作为流动相进行梯度洗脱;用IonSwift MAX-100毛细管柱进行分离;在喷雾电压为3.0 kV、喷雾气压强为2 000 kPa、成源温度为275℃的条件下,选择离子监测(SIM)模式下运行质谱。结果表明,柠檬酸和异柠檬酸两种同分异构体能够得到很好的分离,8种有机酸在一定浓度范围内具有良好的线性关系,相对标准偏差为1.45%~5.99%,相关系数为0.9696~0.9986,平均加标回收率为89.0%~110.0%,8种有机酸的检出限为0.01~0.50 mg/L。该方法进样量少,灵敏度高,重现性好,能够满足实际样品的检测要求,可用于嗜热厌氧菌发酵液中低分子量有机酸的测定。     

高效液相色谱法同时测定多维元素片中9种水溶性维生素

采用更简便的流动相体系,建立了高效液相色谱法同时测定多维元素片中9种水溶性维生素的快速分析方法。以酸水解与离心的方法处理样品,用C8柱分离,流动相A为0.1%三氟乙酸的水溶液,B为甲醇,梯度洗脱,二极管阵列检测器(DAD)检测。28min内实现了9种水溶性维生素的同时分离测定。各维生素线性关系、精密度、回收率均良好。并使用美国国家标准技术研究院(NIST)的SRM3280多维元素片标准物质对方法进行了确认,运用此法测定了市售多维元素片中的水溶性维生素含量。该法可作为维生素片剂中水溶性维生素分离测定的质控方法。     

婴儿配方奶粉中8种水溶性维生素的高效液相色谱同时测定

采用改进后的流动相体系,建立了高效液相色谱同时测定婴儿配方奶粉中8种水溶性维生素(盐酸硫胺素、核黄素、烟酰胺、烟酸、吡哆胺、叶酸、氰钴维生素、抗坏血酸)的快速分析方法.以马尿酸作为内标,Inertsil-ODS-SP柱分离,采用含1 mmol/L七氟丁酸的磷酸二氢钾水溶液和乙腈作为流动相,梯度洗脱,紫外检测器,16 min内实现8种维生素的同时分离测定.对4种婴儿配方奶粉中的8种维生素进行测定,加标回收率在97%～105%,相对标准偏差在0.2%～2.3%.     

梯度洗脱高效液相色谱法快速检测厌氧菌代谢物中的有机酸

提出了一种快速分析厌氧细菌代谢物中5种有机酸的高效液相色谱方法。该方法采用乙腈-0.02mol/L磷酸二氢钾缓冲溶液(pH 2.8)作为流动相,流速和流动相中两种组分的比例均采用四元泵程序梯度洗脱方法控制,检测波长为215 nm,柱温30℃时,能够快速、准确地分离和测定细菌培养基中的甲酸、乙酸、乳酸、琥珀酸和丙酸等5种有机酸,总分析时间只需4 m in。方法的相对标准偏差为0.26%~1.26%,回收率95.0%~100.8%,各种有机酸的线性相关系数r≥0.99981,具有较高的精密度和准确度,可以用于细菌代谢物中有机酸的分析。     

高效液相色谱法测定1,3-丙二醇发酵液中的有机酸

采用高效液相色谱法在Kromasil C18色谱柱(5 μm,250 mm×4.6 mm i.d.)上测定了1,3-丙二醇发酵液中的有机酸,流动相为0.2%(V/V)磷酸和乙腈混合溶液(体积比为96.53.5),发酵液经氯仿处理后直接分离定量,8 min内可将发酵液中的甲酸、乳酸、乙酸、琥珀酸、柠檬酸及延胡索酸完全分离定量.流动相流速为1.0 mL/min,紫外检测波长为214 nm,柱温为20℃.方法的回收率为97.7%～100.5%;RSD为0.98%～2.35%.实验结果表明,该法是测定发酵液中有机酸的快速、有效的定量分析方法.     

RP-HPLC法测定SO_2处理前后新疆无核葡萄干中的B族维生素

建立了高效液相色谱同时测定SO_2处理前后无核葡萄干中4种B族维生素(V_(B1),V_(B2),V_(B3)和V_(B6))的分析方法。考察了流动相组成、p H值及梯度洗脱程序对分离效果的影响。最终采用pH 4.4缓冲溶液和乙腈作为流动相进行梯度洗脱,4种B族水溶性维生素的线性范围为0.1~20 mg/L,r20.999,检出限为0.013~0.064 mg/L,方法的平均回收率为83.0%~101.4%,相对标准偏差为0.6%~4.8%。同时利用该法对SO_2处理前后无核葡萄干中4种维生素含量的影响进行研究。结果表明,空白无核葡萄干中V_(B6)的含量最大,V_(B1)含量较低;但SO_2处理对葡萄干中V_(B1)的含量影响最大,其它3种B族维生素的含量变化不大。该方法简便,快速,准确性和重现性均较好,可用于葡萄干中B族维生素的测定。     

固相萃取-超高效液相色谱法同时测定乳制品中6种有机酸

建立了固相萃取-超高效液相色谱(UPLC)同时测定乳制品中苹果酸、酒石酸、乳酸、乙酸、柠檬酸、富马酸等6种有机酸的分析方法。样品用体积分数1%氨水溶液提取,调节至中性后经MAX柱净化,用Acquity UPLC HSS T3色谱柱(2.1 mm×100 mm,1.8μm)分离,以乙腈和0.02 mol/L KH2PO4缓冲溶液(pH 2.0)作为流动相进行梯度洗脱,二极管阵列检测器检测。6种有机酸在其相应范围内(0.05~5000 mg/L)线性关系良好(r2≥0.999),方法的定量限(信噪比为10)为0.05~25.0 mg/kg,3个不同水平的添加浓度回收率为80.1%~103.2%,相对标准偏差(n=8)在1.9%~11%之间。方法适合于乳制品中6种有机酸的同时检测。     

微乳液相色谱法同时分离7种水溶性维生素

采用微乳液相色谱法同时分离7种水溶性维生素(V_(B1)、V_(B2)、V_(B6)、VB_(12)、叶酸、烟酰胺和VC)。考察了微乳流动相体系中表面活性剂、油相、助表面活性剂的种类以及流动相的pH值、柱温等对水溶性维生素分离的影响。优化后微乳体系的组成为:十二烷基硫酸钠(SDS)/聚氧乙烯月桂醇醚(Brij35)/正丁醇/乙酸乙酯/水(质量比为2∶60∶66∶8∶864)。色谱柱为Agilent TC C18(250 mm×4.6 mm,5μm),柱温为30℃,检测波长为254 nm,流速为0.5mL/min。7种水溶性维生素在20 min内达到基线分离。在4~36 mg/L范围内,7种水溶性维生素的质量浓度与峰面积的相关系数均大于0.999 1。不同添加水平下,V_(B1)、V_(B2)、V_(B6)、VC和烟酰胺的平均回收率为93.9%~102.9%。该方法可用于食品和药品中的多种水溶性维生素的分离、鉴别及快速测定。     

高效液相色谱-串联质谱法同时测定配合饲料中维生素B_1和维生素B_2

采用高效液相色谱-串联质谱法同时测定配合饲料中维生素B1和维生素B2。样品经20mmol·L-1甲酸铵溶液提取后,采用Tigerkin C8色谱柱分离,以甲醇-20mmol·L-1甲酸溶液为流动相进行梯度洗脱,采用电喷雾正离子源-选择多反应监测模式检测,外标法定量。维生素B1和维生素B2的质量分数在20.0~500μg·kg-1范围内与其峰面积呈线性关系,检出限(3S/N)均为50μg·kg-1。对虾饲料进行加标回收试验,回收率在88.0%~120%之间,测定值的相对标准偏差(n=6)为0.90%~2.7%。方法已应用于市售配合饲料中维生素B1和维生素B2的测定。     

反相HPLC同时测定产琥珀酸放线杆菌发酵液中的有机酸与葡萄糖

提出了一种利用高效液相色谱法同时分析产琥珀酸放线杆菌发酵液中葡萄糖和有机酸的方法。在EclipseXDB C8(150mm×Φ4.6mm,5μm)色谱柱上,以5mmol LH2SO4溶液(pH2.5)作流动相,流速为1mL min,采用示差折光检测器,一次进样可同时定性及定量分析待测试样中的有机酸及葡萄糖,每一样品的分析时间不超过9min。确定了测定各物质的工作曲线的回归方程、线性范围、相关系数和检出限。测定发酵液中葡萄糖、琥珀酸和副产物乳酸的相对标准偏差在0.41%～0.89%范围内,平均回收率在99.6%～100.8%之间。     

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.