柱前衍生化气相色谱法分析豌豆根尖粘液中的多糖

采用三氟乙酸水解豌豆根尖粘液中的多糖,衍生化后用气相色谱分离测定6种单糖.实验表明,根尖粘液用三氟乙酸水解并乙酰化,采用OV-17石英毛细管色谱柱(35 m×0.32 mm, 0.33 μm),利用气相色谱法对6种单糖进行分离测定,6种糖全部达到基线分离,总分析时间为42 min.用保留时间定性,外标法定量.方法线性范围为0.0025～2.5 g/L,各标准曲线相关系数r>0.9991; 检出限0 0216～0.1578 mg/L,加样回收率为96.7%～107.4%.实验结果表明,本方法可有效测定逆境胁迫下植物根尖粘液中的糖类物质.     

气相色谱法测定多糖样品中单糖的含量北大核心CSCD

提出了测定多糖样品中单糖含量的气相色谱法。10.00 mg多糖样品经0.4 mL4mol·L-1三氟乙酸溶液于100℃水解5h变为单糖,再进行乙酰化。所得溶液采用气相色谱法进行分离测定。以DB-5色谱柱为固定相,采用分流比为10∶1的分流模式进样。6种单糖的质量浓度在2.00～100.00mg·L-1内与其峰面积呈线性关系,检出限(3S/N)为0.11～0.18mg·L-1。按标准加入法进行回收试验,回收率为88.0%～110%,峰面积的相对标准偏差(n=6)为1.3%～2.3%。     

气相色谱法测定芦荟及芦荟干粉中的多糖

用气相色谱法测定了芦荟及芦荟干粉样品中的多糖。实验以木糖醇为内标物,采用以OV-225与OS-138为固定液的色谱柱,使多糖水解为单糖后的衍生物得到了分离。结果表明:未经水解的芦荟中含有少量的单糖,主要为葡萄糖;水解后的单糖主要为甘露糖和葡萄糖。这与用乙醇沉淀多糖后的测定结果(即芦荟及芦荟干粉中的多糖主要为甘露聚糖和葡甘露聚糖)是一致的。     

气相色谱法测定芦荟及芦荟干粉中的多糖

提取芦荟及芦荟干粉样品中的多糖，将多糖水解为单糖之后衍生化反应，用气相色谱法进行分析，实验选择了最佳分离条件，以木糖醇为内标物，用OV-225与OS-138为色谱柱固定液，使衍生物得到了很好的分离，结果表明：未经水解的芦荟中含有少量的单糖以葡萄糖的形式存在，水解后的单糖主要为甘露糖和葡萄糖，这与用乙醇沉淀多糖后测定结果一致，即芦荟及芦荟干粉中的多糖主要为甘露聚糖和甘露葡聚糖。     

高效阴离子交换-脉冲安培检测同时分析单糖和糖醛酸

建立了高效阴离子交换-脉冲安培检测(HPAE-PAD)同时分离测定8种单糖和2种糖醛酸的分析方法。以CarboPacPA20阴离子交换柱为分离柱,以2mmol/LNaOH溶液将8种单糖从分离柱上洗脱,而后用NaAc(50~200mmol/L)梯度淋洗2种糖醛酸,淋洗液流速为0.5mL/min,总分析时间为30min。在优化的分离测定条件下,8种单糖和2种糖醛酸的检出限为2.5~14.4μg/L(进样体积25μL,峰面积定量)。5mg/L的10种化合物的混合标准溶液连续7次进样,峰面积的相对标准偏差为0.3%~1.5%。用所建立的方法测定了多糖水解液和木材半纤维素水解液中的单糖和糖醛酸含量。     

气相色谱法测定驱蚊功效印刷品中3种功效化合物

建立了气相色谱–氢火焰离子技术测定功效印刷品中3种驱蚊成分的方法。样品用二氯甲烷进行超声提取,邻苯二甲酸二丁酯为内标,利用毛细管色谱柱HP–5(30 m×0.32 mm,0.25μm)分离,保留时间定性,内标法定量。结果表明,3种驱蚊功效物质色谱分离良好,在质量浓度0.1~1.0 mg/L范围内与色谱峰面积呈线性相关。方法定量限(10S/N)为1.25 mg/kg,样品加标回收率为97%~108%,测定结果的相对标准偏差不大于8.1%(n=6)。该方法快速、可靠、准确、简便,适用于驱蚊功效的印刷品中3种驱蚊功效类化合物的分析检测。     

高效阴离子交换色谱-脉冲安培检测法分析漏芦多糖中单糖组成

采用高效阴离子交换色谱-脉冲安培检测法(HPAEC-PAD),建立了一种测定漏芦多糖中单糖组成的方法.水提、醇沉法提取粗多糖,Sevage法除蛋白,用2mol·L-1硫酸在100℃水解多糖,以CarboPac PA10色谱柱(2mm×250mm)为分离柱,100 mmol·L-1氢氧化钠溶液为淋洗液,流速为1.0 mL·min-1,脉冲安培检测,总分析时间为6min.测定漏芦多糖中单糖组成为阿拉伯糖、葡萄糖和果糖,其摩尔比为1.55:1.00:2.10;加标回收率为93.0%～107.8%,捡出限为2.8～12.3 μg·L-1.     

气相色谱-质谱法测定电子烟烟液中的7种溶剂

提出了测定电子烟烟液中乙醇、1,2-丙二醇、丙三醇、二甘醇、三甘醇、四甘醇和五甘醇等7种溶剂的气相色谱-质谱法(GC-MS)。电子烟烟液经甲醇稀释超声提取后,用DB-ALC1毛细管色谱柱(30m×0.32mm,1.8μm)分离,并用GC-MS进行分析,以1,3-丁二醇为内标物,采用内标法定量。7种溶剂的质量浓度与其峰面积在一定范围内呈线性关系,方法的测定下限(10s)为1.1~5.0mg·L~(-1)。加标回收率在91.2%~107%之间,相对标准偏差(n=5)在1.2%~3.5%之间。     

HPLC-ESI-MS联用法测定灵芝胶囊多糖的单糖组成

建立了测定灵芝胶囊中多糖含量与单糖组分的高效液相色谱-电子喷雾离子源-质谱联用(HPLC-ESI-MS)检测方法,研究了灵芝多糖酸水解为单糖及1-苯基-3-甲基-5-吡唑啉酮(PMP)衍生化的条件,三氟乙酸(TFA)的浓度在0.5 mol/L、水解温度70℃、水解时间30 min时能将灵芝多糖完全水解为单糖,在70℃PMP衍生化反应30 min,4℃冷却,得到双分子PMP单糖衍生物。5种水解后的单糖线性范围为0.1~50 mg/L,检出限为25μg/L(S/N≥3),在3个加标水平(0.1,10,50 mg/g)下,5种单糖平均回收率为95%~105%,精密度(RSD)为0.5%~3.5%。方法能满足对灵芝胶囊质量控制的检测要求。     

毛细管型离子色谱-脉冲安培法检测枸杞多糖的单糖组成

采用ICS-5000毛细管离子色谱仪对枸杞多糖中的10种单糖进行了分离测定.优化了前处理过程中影响多糖水解的酸种类、酸浓度、水解温度和时间等参数,优化条件为使用2 mol/L三氟乙酸溶液在100℃下水解120min,在该条件下,果糖回收率约为50％,其余单糖回收率在84％～104％之间.采用新型淋洗液自动发生装置电解产生淋洗液,Capillary CarborPac PA20色谱柱分离,毛细管安培池检测,10种单糖成分标准曲线线性关系良好,相关系数均大于99.9％;检出限在2.5～75 μg/L之间,为枸杞多糖中单糖组分测定提供了新的可行方法.     

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.     

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.     

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.     

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.