阀切换-离子色谱法测定分析纯硫酸钠中痕量氯离子

建立了阀切换-离子色谱法测定分析纯硫酸钠固体中痕量氯离子含量的方法。ICS-2100离子色谱系统,配置十通阀,用IonPac AS18色谱柱将硫酸钠固体样品中的氯离子和硫酸根离子预分离后,以IonPac TAC-ULP1为富集柱,将氯离子富集后在相同的IonPac AS18色谱柱上进行定量分析。同时以淋洗液发生器产生的不同浓度的KOH作为淋洗液,以抑制型电导检测器测定氯离子的含量。结果表明,阀切换-离子色谱法测定分析纯硫酸钠固体中的痕量氯离子,检出限为10 μg/L,线性相关系数(r2)大于0.999,实际样品的加标回收率为98.0%～103.0%,具有分离度和灵敏度高,选择性好,操作简单等特点。该方法能够准确测定硫酸钠固体中痕量氯离子的含量,适用于高纯化学试剂中痕量氯离子的分离测定。     

单泵柱切换离子色谱法分析复杂基体中痕量阴离子

本文通过离子色谱与柱切换技术联用实现了高浓度样品基体中的痕量阴离子检测.分别研究了不同类型基体的处理方法,使用商品化离子排斥柱和自制的聚合物色谱柱实现多种样品基体中痕量阴离子的检测.同时开发一种简化的单泵柱切换系统,利用抑制器将KOH淋洗液转化为水作为前处理柱的淋洗液,在同一个色谱系统中产生两种淋洗液,实现色谱分离与前...     

超高含量氯离子基体下痕量亚硝酸盐的检测

介绍了一种无需对样品进行除氯处理,采用全新的离子色谱柱,抑制型电导离子色谱法检测,测定超高Cl-基体下痕量亚硝酸盐及其它常见阴离子的方法.其中Cl-浓度与亚硝酸盐浓度比可达到50000:1甚至100000:1,实现良好分离.选择色谱条件为:IonPac AS23阴离子交换柱,手工配制碳酸盐淋洗液等度淋洗,抑制型电导检测.污水样品通过Dionex OnGuardⅡRP柱和0.22 μm微孔尼龙膜处理.该方法采用25 μL进样,8种常见阴离子的检出限为0.2～5.8μg/L,线性范围均超过2个数量级,相关系数r在0.9996～0.9999的范围内,连续11次进样检出所有阴离子的RSD均小于5%,加标回收率结果在93%～106%之间.该方法具有选择性好,灵敏度高,操作简单等特点,从根本上解决了高氯离子基体中痕量亚硝酸盐及其它常见阴离子检测的问题,用于实际污水样品的检测.     

直接进样离子色谱法测定磷酸试剂中痕量无机阴、阳离子

选用亲水性强、柱容量高的阴离子分析柱IonPac AS18,以22 mmol/L KOH为淋洗液作等浓度淋洗,直接进样分析了高浓度磷酸中的痕量无机阴离子.选用柱容量较高的阳离子分析柱IonPac CS12A,H2SO4作为淋洗液直接进样分析了磷酸试剂中的痕量阳离子.该方法无需样品前处理,直接进样,电导检测,高浓度磷酸的存在不影响痕量阴离子或阳离子的测定,对所测的无机阴阳离子的检出限均在2.1μg/L以下,测定范围在两个数量级以上,线性相关系数r在0.994 1～0.999 9范围内,样品中待测离子峰面积的RSD在3.8%以下(n=7),回收率在91%～109%之间.     

柱切换离子色谱法测定丙酮中痕量阴离子

建立了测定丙酮中痕量阴离子的离子色谱分析方法.采用的是高效液相柱切换进样,其中泵的流速为0.5 mL/min,使低浓度的丙酮水溶液在保护柱上富集,通过离子色谱抑制电导法分离和检测丙酮样品中痕量的阴离子.色谱条件为:以IonPacAG9-HC(50 mm×2 mm)型柱串联在定量环中进行富集,IonPacAG9-HC(50 mm×2 mm)保护柱,IonPac AS9-HC(250 mm×2 mm)阴离子分离柱进行分离,流动相为9 mmol/L Na2CO3-1.667 mol/L NaHCO3,所得回收率在96.21%～101.56%之间,线性良好,且具有较好的重现性和较低的检出限.     

毛细管离子色谱-柱切换法测定高纯氢氟酸中痕量阴离子

建立了毛细管离子色谱-柱切换法测定高纯氢氟酸中的痕量阴离子的方法。实验中所考察的保留时间和峰面积的相对标准偏差(RSD)分别为:0.02%～0.12%和0.63%～1.89%,在1～100μg/L线性范围内,线性相关系数大于0.9998,考察的阴离子检出限为2.13～32.61ng/L,加标回收率为85.3%～103.9%,并用于实际样品检测,取得了很好的效果。     

柠檬酸试剂中痕量无机阴阳离子的离子色谱法测定

选用柱容量较高、亲水性较强的阴离子分析柱IonPac AS18,以30mmol／L KOH为淋洗液,等度淋洗分析了高浓度柠檬酸中的痕量无机阴离子。选用柱容量较高的阳离子分析柱IonPac CS12A,以H2SO4作淋洗液分析了柠檬酸试剂中的痕量阳离子。在所选色谱条件下,无需样品前处理,直接进样,电导检测,高浓度柠檬酸不影响痕量阴离子或阳离子的测定。方法具有良好的线性(r=0．9941～1．000),样品中所测离子峰面积的相对标准偏差(RSD)均在9．0％以下(n=7),回收率在82．7％～110％之间,检出限低于3．7μg/L。     

大体积直接进样离子色谱法测定饮用水中痕量溴酸盐

建立了一种无需样品前处理,直接大体积进样,电导检测饮用水中痕量溴酸盐的离子色谱新方法。分析柱为容量高、亲水性强的Dionex IonPac AS19阴离子交换柱,EG40在线产生KOH淋洗液,等浓度泵作梯度淋洗。该方法对溴酸盐的检出限为0．2μg／L;在1～100μg/L范围内具有良好的线性（r=0．9996）。将该方法用于北京市自来水和市售瓶装水样品中痕量溴酸盐的检测,实际样品的加标回收率在90％～106％之间;1μg／L溴酸盐连续进样10次,相对标准偏差（RSD）为5．7％。     

离子色谱柱切换法测定氟化盐高纯试剂中的阴离子杂质

建立了一种测定高纯氟化盐试剂中杂质阴离子的离子色谱柱切换技术分析方法。在纯水流动相下,采用IonPac ICE-AS6离子排斥柱将待测杂质Cl^-,SO₄^2-,NO₄^-及PO₄^3-从高浓度的氟化盐溶液中分离出来,分离出的待测组分富集于IonPac TAC ULP1浓缩柱上。以4.5 mmol/L Na₂CO₃-0.8 mmol/L NaHCO₃为淋洗液,流速1.2 mL/min,经过柱切换,将待测离子从浓缩柱上洗脱下来,通过IonPac AG23（50 mm×4 mm）和IonPacAS23（250 mm×4 mm）色谱柱进行分离,抑制电导检测器检测。本方法在线性范围内,Cl^-,NO₃^-,PO₄^3-和SO₄^2-的相关系数分别为0.9996,0.9999,0.9998和0.9997;加标回收率为92.0%～103.5%;相对标准偏差RSD（n=7）均小于3.0%;检出限（S/N=3）分别为0.2,0.6,3.0和0.5 mg/kg。     

二维离子色谱法同时测定环境水样中的碘离子、硫氰酸根和高氯酸根

建立了二维离子色谱法同时测定环境水样中的碘离子、硫氰酸根离子和高氯酸根离子的方法。先采用常规阴离子色谱柱(IonPac AS16, 250 mm×4 mm)将水样中的碘离子、硫氰酸根离子和高氯酸根离子与干扰离子进行分离。样品溶液通过抑制器后,将含有碘离子、硫氰酸根离子和高氯酸根离子的淋洗液导入富集柱(MAC-200, 80 mm×0.75 mm),再通过毛细管阴离子色谱柱(IonPac AS20 Capillary, 250 mm×0.4 mm)进行分离和定量分析。方法的线性范围为0.05～100 μg/L,相关系数达到0.9999,检出限为0.02～0.05 μg/L。样品中碘离子、硫氰酸根离子和高氯酸根离子的加标回收率在85.1%～100.1%之间,回收率的相对标准偏差(RSD)(n=6)在1.7%～4.9%之间。该法试剂用量小,灵敏度比常规离子色谱提高30～40倍,同时去除了样液中的高浓度基体杂质,适用于水样中低含量碘离子、硫氰酸根离子和高氯酸根离子的检测。     

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.