微型柱现场预富集流动注射火焰原子吸收光谱法测定环境水样中钴

以负载8-羟基喹啉(Oxine)、二乙基二硫代氨基甲酸钠(DDTC)和吡咯啶二硫代氨基甲酸铵(APDC)三种螯合剂的活性炭为微型柱的吸附材料,采用微型柱现场采样分析技术实现了连续现场富集环境水样中痕量钴,并在实验室中采用在线解吸流动注射火焰原子吸收光谱法对吸附柱中富集的钴进行了测定.该方法用于环境水样中钴的测定,10 mL富集水样的检出限(3σ)为1.13μg·L-1,分析了3件水样中的钴,测定结果的RSD(n=6)值均小于1 %.     

环境水样中镍的微型柱现场预富集流动注射火焰原子吸收测定

以负载8-羟基喹啉(Oxine)、二乙基二硫代氨基甲酸钠(DDTC)和吡咯啶二硫代氨基甲酸铵(APDC)3种螯合剂的活性炭(AC)为微型柱的吸附材料,采用微型柱现场采样(MFS)分析技术实现了连续现场富集环境水样中的痕量Ni,并在实验室中采用流动注射(FI)-火焰原子吸收(FAAS)联用技术对吸附柱中富集的Ni进行了测定。该方法用于环境水样中Ni的测定获得了满意的结果。10 mL水富集Ni的检出限(3δ)为2.62μg.L-1,相对标准偏差为1.02%。     

硅藻土吸附在线柱富集-火焰原子吸收光谱法测定环境水样中痕量铜

提出了硅藻土吸附在线柱富集-火焰原子吸收光谱法测定环境水样中痕量铜的方法。利用硅藻土对环境水样中痕量铜在线预富集,浓集因子达到27.6,使火焰原子吸收光谱法的检测能力达到测定环境水样中痕量铜的要求。方法检出限为0.32μg.L-1,RSD(20μg.L-1)为3.52%,加标回收率为97.0%~105.0%。     

地质样品中金银的连续快速测定——二苯硫脲-三正辛胺棉富集分离液珠萃取比色法

采用二苯硫脲(DPTU)—三正辛胺(TNOA)棉富集分离金、银已有报道。本文采用该吸附剂制备了DPTU—TNOA棉吸附柱,并研究了动态法富集分离金、银的条件。研究表明.吸附柱富集金、银的最佳酸度(体积分数)为5％～20％王水。当含金溶液以1～6ml·min~(-1)流速通过0.1g吸附剂制备的吸附柱时,金、银的吸附率均在98％以上。采用硫代米蚩酮(TMK)液珠萃取比色法连续测定了地质样品中的金、银。方法的检出限为0.5×10~(-9),银为5×10~(-9)。经样品验证,其分析结果满足化探找金工作的需要。     

流动注射微柱预富集等离子体原子发射光谱法测定高纯锌中痕量稀土元素

本文报道以DCS-偶氮胂固定于活性炭上作为固定相,用于流动注射微柱预富集体系和等离子体原子发射光谱测定痕量稀土元素.测定了吸附材料对稀土元素的静态和动态吸附容量,分别达几十和几个mg/g吸附材料;对影响柱预富集的PH、上柱速度、洗脱酸度、柱尺寸等因素进行了详细考察;在优化条件下,富集倍数为10倍左右.对La、Nd、Eu、Gd、Tb、Dy、Ho和 Lu等元素的检出限为 μg/L级,RSD在 1.5％～3.9％之间(n=6,单一稀土浓度0.085 mg/L).该法应用于高纯锌中痕量稀土元素的测定,试样加入回收率在 84.5％～97.6％之间,分析结果满意.     

磷酸三丁酯萃淋树脂富集水中痕量酚类化合物的研究

本文对磷酸三丁酯（ＴＢＰ）萃淋树脂为柱填料，研究了富集水中酚类化合物及其洗脱条件。结果表明，以ＴＢＰ萃淋树脂为富集剂，水样ｐＨ值为１－７，以３０ｍｌ／ｍｉｎ的流速通过吸附柱，用８ｍｌ０．１ｍｏｌ／Ｌ的ＮａＯＨ洗脱，多种酚类化合物回收率在９７％－１０３％。此外还试验了地面水中常见干扰物的影响，该方法富集倍数达１２５倍，最低检测限０．５μｇ／Ｌ。对实际样品１－１００μｇ／Ｌ范围内的测定相对标准偏差４．     

固相萃取-高效液相色谱法测定水中的多环芳烃

建立了固相萃取-一高效液相色谱法测定水中多环芳烃的方法。水样经L-18固相萃取柱吸附后用二氯甲烷洗脱,氮吹干后换甲醇溶剂。反相C18柱为色谱柱;水、甲醇为流动相进行梯度洗脱,流速为1．0mL／min;柱温为30℃;检测器为荧光检测器、紫外检测器。方法的检出限为0．00006-0.03μg／L,回收率为80％～110％,测定结果的相对标准偏差为0．1％～3．6％（n=5）。方法适合于水中16种多环芳烃的测定。     

四-（对甲氧基苯基）-卟啉柱前衍生，固相萃取高效液相色谱法测定痕量铁、钴、铜、锌和锰

研究了用固相萃取富集，高效液相色谱法测定环境水样中痕量Fe、Co、Cu，Zn和Mn的方法。环境水样中的Fe、Co、Cu、Zn和Mn用四-(对甲氧基苯基)-卟啉(T4MPP)柱前衍生，用Waters Sep—Pak—C18固相萃取小柱萃取富集Fe、Co、Cu、Zn和Mn的T4MPP络合物，富集倍数达50倍；然后用甲醇和四氢呋喃梯度洗脱为流动相，Waters Xterra^TM RP18色谱柱为固定相分离，用二极管矩阵检测器检测。Fe、Co、Cu、Zn和Mn的检测限分别为：3．2、1．8、2．0、2．0和4．5ng/L。方法相对标准偏差为2．1％～3．7％，标准回收率为94％～107％。该方法用于环境水样分析，结果令人满意。     

海带吸附法分离富集水样中痕量铅和镉

研究了用海带吸附法分离富集水中痕量Pb2 和Cd2 的方法.在25℃下,pH4.0～5.0,水样经过预先用海带制成吸附柱后,用10mL 1 mol/L的HCl,流速为1 mL/min对吸附柱进行洗脱,采用原子吸收光谱法测定洗脱液中Pb2 和Cd2 .Pb2 和Cd2 的饱和吸附量分别为164.67和8.73 mg/g,回收率在95.8%～103.1%之间.     

活性炭富集二苯偶氮羰酰肼分光光度法测定水中痕量钒

采用粒径≤９０μｍ 活性炭吸附富集天然水中痕量钒,并用二苯偶氮羰酰肼分光光度法测定。研究了钒在活性炭上的吸附行为和解吸条件。采用在ｐＨ３～４．５ 的条件下吸附,１ ｍ ｏｌ／ＬＮａＯＨ 溶液洗脱,本法富集倍数达１００ 倍,样品中钒的检出下限为３．９×１０－ ９ｇ／Ｌ ,标准加入回收率为８８％ ～１０３％ ,相对标准偏差小于１０％ 。方法已用于自来水,漓江水等环境水样中痕量钒测定。     

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.