用萃取-氢化物发生-原子荧光光谱法测定海带中的无机砷

利用无机砷在强酸性下能溶于氯仿,在弱酸性下能溶于水的特点,将其与其他干扰物质分离,采用氢化物发生-原子荧光光谱法测定海带中的无机砷.利用9mol/L HCl溶解海带样品后用三氯甲烷萃取其中的无机砷,再反萃取于1 mol/L HCl溶液中,干燥-消化后,用氢化物发生-原子荧光光谱法测定其中无机砷的含量.重要干扰物-二甲基亚砷酸不会被同时萃取,方法的回收率在80%以上.     

无机填料表面改性剂的成分分析

无机填料的表面改性剂以氯仿为溶剂进行溶解,所得滤液采用气相色谱-质谱法分离测定各种成分,采用峰面积归一化法定量。按其总离子流图共鉴定了17种化学成分,其中3种主要成分及含量为棕榈酸(48.50%),石蜡(29.88%)和硬脂酸(11.97%)。滤渣采用红外光谱法分析,其主要成分为氧化聚乙烯蜡。     

一次性塑料餐具中风险物质的筛查

研究筛查和识别了一次性餐具(餐盒、杯子和吸管)中向食品模拟物10%乙醇和化学替代溶剂95%乙醇迁移的物质种类,以评估迁移物及一次性塑料餐具的安全风险。采用10%乙醇或95%乙醇在特定迁移条件下浸泡样品,浓缩浸泡液,用气相色谱-质谱仪(GC-MS)测定浓缩液中的物质,通过比对质谱数据库并结合红外光谱仪得到的样品信息,推测迁移物结构,并通过对比对照品或三重四极杆质谱分析方式确认。利用Cramer规则预测识别迁移物的毒性,结合测定的迁移量判断迁移物安全风险。在测试样品中识别出19种迁移物,其中有意添加物包括聚乳酸树脂及共混树脂的合成原料、润滑剂、增塑剂等,非有意添加物包括聚酯及有机硅树脂中的低聚物和增塑剂、抗氧剂中的杂质或副产物等。聚丙烯材质餐具中迁出的物质种类较少,而聚乳酸材质餐具以及无机填充聚丙烯餐具中迁出的物质种类相对较多;多数迁移物在95%乙醇中迁移量高于在10%乙醇中迁移量。安全评估结果显示,在含油脂食品模拟物中,聚乳酸或无机填充聚丙烯餐具中环状硅氧烷等低聚物和抗氧剂副产物等非有意添加物的迁出危害需引起关注。     

气相色谱-场电离-高分辨飞行时间质谱联用法测定火箭煤油的烃类组成

采用气相色谱分离与场电离和高分辨飞行时间质谱法(FI-TOF-HRMS)联用研究了火箭煤油的烃类组成、类型分布和碳数分布。分析时将煤油样品直接进样。分析结果表明:此火箭煤油中烃类的碳数分布在C8~C16之间;含直链烷烃量占19.9%(w/%,下同),含总环烷烃量达77.7%(其中包括一环烷烃42.9%,二环烷烃33.4%),含芳烃类杂质(均为单环芳烃)含量仅占2.4%;样品中未测得含硫、氮及氧杂环化合物的杂质。该分析结果与气相色谱-质谱法的分析结果完全一致。     

广东遂溪泥煤蜡和云南寻甸褐煤蜡的化学组成研究

泥煤蜡和褐煤蜡的主要组成物为纯蜡和树脂物质。纯蜡经皂化和溶剂萃取分离,分离物分别用气相色谱和色谱一质谱联合检定,表明进溪泥煤蜡和寻甸褐煤腊中均含有C_(24)～C_(34)偶碳烷醇和C_(16)～C)(34)烷酸。树脂物经皂化和柱层析分离,所得的氯仿洗脱物经红外光谱和~1H校磁热振谱检定证明其中含有β-谷甾醇。泥煤蜡树脂物中的β-谷甾醇主要以α-型形式存在,而褐煤的则为β-型。此外,泥煤蜡树脂物中还检出有雌二醇和雌酚酮类物。     

在线样品制备技术耦合液相色谱-质谱系统在食品危害物检测中的应用进展

食品安全检测具有重要意义,但食品样品基质复杂,测定其中危害物时,通常需要以下几个步骤：样品制备,即采用适合的样品前处理方法,在不同基质中将目标物分离出来;分离纯化,利用色谱系统进一步分离纯化目标物;定性定量分析,基于目标化合物的性质选择合适的检测器进行分析。其中样品制备是关键步骤之一,将样品制备过程与液相色谱系统耦合可以实现样品的在线自动化分析。与传统人工处理过程相比,在线分析不仅能够减少人工操作误差,保证良好的精密度和重复性,而且可以降低溶剂消耗,避免样品间交叉污染,同时节约分析时间,提高检测效率。本文主要介绍目前常用的在线样品制备技术,包括在线固相萃取(on-line SPE)、管内固相微萃取(in-tube SPME)、湍流色谱法(TFC),详细阐述了其基本原理和耦合设备。在线样品制备技术耦合液相色谱-质谱系统分为两个维度,主要依赖于阀切换技术,将样品制备(第一维度)和液相色谱系统(第二维度)之间建立物理连接,随后采用相应的检测器进行分析。第一维度的作用主要是去除样品杂质,净化分离目标物,为第二维度对目标物进行定性定量检测做准备。此外,文章对3种在线净化系统适用的不同净化填料进行...     

高效液相色谱-质谱联用分析洛伐他丁中的杂质

利用高效液相色谱-二极管阵列检测器-质谱联用方法对洛伐他丁及其杂质成分进行分离分析和结构鉴定。实验采用D iamonsil C18(5μm,4.6 mm×250 mm)为分离柱,乙腈-水(含0.1%乙酸)(65∶35)为流动相,分离并检测了洛伐他丁及其杂质;通过与DAD检测器和离子阱质谱联用,获得了它们的紫外光谱和质谱数据;紫外光谱表明除氢化洛伐他丁外其余杂质与洛伐他丁基本结构相同,利用MS和MS2数据确定了杂质的分子量和侧链结构,由此鉴定了其中10个杂质的结构。实验结果表明,高效液相色谱-二极管阵列检测器-质谱联用技术可以快速鉴定洛伐他丁中的杂质化学成分。     

Suwannee河腐植酸光化学生成溶解无机碳的研究

溶解有机质矿化为溶解无机碳是全球碳循环中的一个重要过程.利用模拟太阳光对Suwannee河腐植酸的光氧化过程模拟,研究了溶解氧浓度、模拟太阳光波长范围和铁浓度对溶解无机碳产量的影响.研究表明,基于前24 h空气饱和的无机碳矿化速率4.40μmol/(L.h),氧气饱和条件下照射增加1.56倍,氮气饱和条件下照射下降36%.UV-B,UV-A和可见光部分分别占溶解无机碳产量的31.8%、32.6%和25.6%.当加入20μmol/L铁络合剂DFOM时(初始样品Suwannee河腐植酸铁含量为5.46μmol/L),溶解无机碳产量下降55.6%.     

用二维色谱技术测定丙烯中痕量总硫

]本文利用二维色谱技术,开发了一种新的总硫分析方法。本方法以CuO作陷阱,在650-700温度下,捕捉样品中经氧化生成的SO2,SO3。然后使其在900-950℃温度下变为SO2释放出来。被释放的SO2用载气携入色谱柱,用火焰光度鉴定器FPD测定。同时,CuO起预分离柱的作用,使样品主体成分及其它杂质与含硫化合物分离。由于CuO的富集和分离作用,分析时可以加大进样量浚,提高了方法的灵敏度和准确性。文中还报道了丙烯中加入硫化氢,硫氧碳;乙醇中加入二硫化碳、噻吩、乙硫醚等六种化合物的测定结果。实验表明,气体样进样量为100ml液体样品进样量为100μl时,最低检测庀限可达到PPb级,偏差小于10％。     

X射线衍射法钾混盐无标样定量相分析

采用EVD、TOPAS应用软件和TOPAS结构数据库以及无机晶体结构数据库,对一些混合盐样品(如钾混盐、尾矿等)进行了X射线粉末衍射无标样定量相分析全谱拟合模拟研究。在用Rietveld分析法对上述样品中无机盐成分的X射线衍射谱进行模拟过程中,选择基本参数函数为峰形函数,并通过March-Dolase择优取向校正拟合,提高了拟合精度。测得钾混盐样品中钾盐镁矾相含量为72.44%,岩盐相含量为27.56%,误差值Rwp(17.45),Rp(12.21)和拟合度S(4.91)均有所降低。     

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.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.