氢化物发生-原子荧光光谱法测定高纯铝酸钙粉中砷

采用氢化物发生-原子荧光光谱法对高纯铝酸钙粉中砷的测定进行了研究。样品以盐酸(1+1)、硝酸(1+1)溶解,研究了酸介质及酸浓度、硫脲-抗坏血酸用量对砷测定的影响。在优化的实验条件下,得到砷标准曲线的线性相关系数大于0.999 5。对样品进行了精密度和加标回收实验,得到测定砷相对标准偏差为1.8%～2.6%,加标回收率在98.5%～108%。方法能满足高纯铝酸钙粉中砷的测定。     

高效液相色谱法测定蜈蚣草中二苯砷酸

建立了高效液相色谱法测定蜈蚣草中二苯砷酸的分析方法。样品采用0.1mol·L-1磷酸氢二钠溶液振荡提取4h,高速离心,上清液以Shimadzu VP-ODS反相C18柱为分离柱,以乙腈-0.02mol·L-1磷酸二氢钾溶液(16+84)作为流动相进行洗脱,检测波长为220nm。二苯砷酸的质量浓度在0.20~2.0 mg·L-1范围内与其峰面积呈线性关系,方法的检出限(3S/N)为2.8mg·kg-1。对空白样品进行加标回收试验,加标回收率在98.5%~98.8%之间,测定值的相对标准偏差(n=5)为0.97%~4.6%。方法可应用于蜈蚣草中二苯砷酸的检测。     

原子荧光光谱法测定中药材中砷

试样用硝酸加压消解(测总砷),或用盐酸(1+1)溶液在60℃浸取(测无机砷)。以硫脲溶液作为预还原剂,以硼氢化钾溶液作为还原剂,利用原子荧光光谱法测定中药材中砷的含量。分析中采用载气及屏蔽气的流量依次为400mL·min-1及900mL·min-1。砷(Ⅲ)的荧光强度与其质量浓度在80.0μg·L-1以内呈线性关系,方法的检出限(3s/k)为31ng·L-1。应用此法对中药材样品进行分析,样品中总砷测定值在139～372ng·g-1之间,加标回收率在89.0%～93.3%之间;无机砷测定值在41～103ng·g-1之间,加标回收率在86.0%～92.0%之间。     

氢化物发生原子荧光结合计算法测定大气颗粒物中砷的形态

运用碱式消解法对样品进行前处理,采用氢化物发生-原子荧光光谱数学计算法测定大气颗粒物中As(Ⅲ)和As(Ⅴ)的含量。探讨了还原剂用量、酸介质及其酸度、载气及屏蔽气流量和观测高度等对荧光强度的影响,分析了共存离子对砷测定的干扰。在选定的最佳条件下,得到检出限为0.34μg/L,加标回收率为87.8%～108.2%。方法可用于测定大气颗粒物中不同形态的砷。     

电感耦合等离子体原子发射光谱法测定玻璃澄清剂中砷的前处理方法研究

研究了几种常规前处理方法对玻璃澄清剂中砷测定的影响,建立了一种预氧化处理、后酸式湿分解的前处理方法.较传统碱熔法而言,该方法简单方便且可操作性强,同时可避免传统酸溶分解过程中可能造成的砷挥发损失.对预氧化处理使用的氧化剂和预氧化过程进行了筛选与优化,确定了4种湿式预氧化-酸消化分解方法,并利用端视电感耦合等离子体发射光谱实现了砷的直接测定.通过精密度和准确度实验,得到4种方法的相对标准偏差均小于2%,样品的加标回收率为98% ～106%,表明该前处理方法准确度高、精密度好.将所建立的分析方法用于玻璃澄清剂样品的测定,结果令人满意.     

ICP-MS测定西藏热泉水中总砷

西藏地区热泉水矿化度较高,不同类型热泉水砷含量差异大。为快速准确测定其中砷的含量,建立了碰撞模式-电感耦合等离子体质谱测定热泉水中总砷的方法。研究了样品保存条件、样品稀释倍数、KED气流量等条件对测定结果的影响。通过优化仪器的工作条件、样品稀释等方法,消除了低分压和高矿化度的影响,运用碰撞池技术,有效消除⁴⁰ Ar³⁵Cl⁺、⁴⁰Ca³⁵Cl⁺、³⁹ K³⁶Ar⁺对砷的干扰。在样品中加入乙醇溶液,提高砷的灵敏度。结果表明:砷的检出限(3s)为0.22μg·L^-1,加标回收率在91.01%～108.96%之间,测定值的相对标准偏差(n=6)为2.2～4.5%,方法可以快速、准确测定西藏热泉水中总砷。     

动物排泄物中无机砷和有机砷测定方法研究

本文建立了微波辅助提取-氢化物发生-原子荧光光谱法测定服用有机砷饲料后猪排泄粪便中的无机砷和有机砷的方法.研究了微波辅助提取的最佳条件,考察了酸介质、还原剂的选择及共存离子的干扰及消除方法.方法的检出限为0.20 μg\5L-1,相对标准偏差(RSD)为1.3%,样品加标回收率为95.2%～97.2%.     

高效液相色谱-电感耦合等离子体质谱联用技术测定水产类膳食中5种砷形态的方法研究

采用高效液相色谱(HPLC)和电感耦合等离子体质谱(ICP-MS)联用技术建立了三价砷As(Ⅲ)、砷甜菜碱(AsB)、二甲基砷酸(DMA)、一甲基砷酸(MMA)、五价砷As(Ⅴ)5种砷形态的分析方法。采用超声溶剂提取法对水产类膳食样品和带鱼等水产品进行前处理后,对砷形态进行分析。实验表明,5种砷化合物的线性范围为2.5~500μg/L,相关系数(r)均大于0.999 0,检出限为0.6~0.9μg/L,RSD均小于5%。采用加标回收考察方法的准确性,加标回收率为87%~124%。样品的测定结果显示,水产品及水产类膳食中砷形态的主要存在形式为砷甜菜碱。     

高效液相色谱-电感耦合等离子体质谱联用技术测定花茶中砷形态

应用高效液相色谱-电感耦合等离子体质谱(HPLC-ICP-MS)联用技术,建立了花茶中6种砷形态:亚砷酸根、砷酸根、一甲基砷酸、二甲基砷酸、砷胆碱、砷甜菜碱的分析方法。样品在真空条件下采用水-磷酸进行提取,用Hamilton PRP-X100阴离子交换柱,以碳酸铵溶液和硝酸铵+磷酸氢二铵作为流动相进行梯度洗脱,电感耦合等离子体质谱进行定性和定量分析。方法学验证表明:在0.5～50μg/L范围内各砷形态线性良好,线性相关系数(r2)都大于0.999,定量限为0.5μg/L,加标回收率在89.9%～104.1%之间,相对标准偏差(RSD)在1.4%～4.2%之间。方法适用于各类花茶中的6种砷形态分析。     

微波消解–原子荧光光谱法测定卷烟中的砷

采用微波消解、氢化物发生–原子荧光光谱法测定烟丝、过滤材料和接装纸样品中的砷,确定了样品前处理的最佳条件与仪器测定条件。砷浓度在0～40 ng/mL之间时,标准工作曲线的线性相关系数大于0.999,砷的检出限为1 ng/g。通过测定国家标准物质和加标回收试验进行了方法验证,精密度和准确度均能满足样品的测试要求。在试验条件下,测定样品中砷的加标回收率为92%～102%,测定结果的相对标准偏差小于4.0%(n=5)。     

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.