CL-7301微色谱柱分离铀化合物中痕量镉的方法研究

采用CL-730l树脂微色谱柱研究了铀化合物中基体铀和痕量镉的分离条件,并用在线富集法测定了铀化合物中的痕量镉.通过试验选择0.125mol/L的HI酸介质中,镉的吸附率接近100%,而铀不被吸附,分离效率达到99.9%以上.吸附在柱上的镉用10 g/L EDTA 洗脱,原子吸收光度法测定.利用在线富集技术,镉的检出限降低至2.3μg/L.对八氧化三铀和分析纯醋酸双氧铀样品中痕量镉进行测定,方法精密度为1.5%,加标回收率为96%～98%.     

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.     

浊点萃取-石墨炉原子吸收光谱法同时测定生物样品中痕量铅和镉

提出了石墨炉原子吸收光谱法同时测定小鼠肝中痕量Pb和Cd的方法。以8-羟基喹啉为络合剂,在pH 9.0时,用Triton X-100浊点萃取富集样品中的Pb和Cd。用NH4H2PO4作为基体改进剂测定Pb和Cd,Pb和Cd的检出限(3s/k)分别为0.103μg/L和0.0136μg/L,相对标准差(n=6)分别为1.4%,0.73%。对于10 mL样品溶液的富集倍数分别为7.1,9.3。利用该法分别测定了小鼠肝中的Pb和Cd的含量,加标回收率分别为96.4%～97.1%和101.3%～103.2%。     

流动注射-微柱在线富集/电感耦合等离子发射光谱法测定中成药中痕量铅和镉

采用自制固相萃取材料PTFE-g-GMA-PEI纤维填充微柱预富集和流动注射(FI) 与电感耦合等离子发射光谱仪联用, 测定样品中痕量Pb2+和Cd2+.对Pb2+和Cd2+的富集与洗脱条件进行优化,并给出相应离子的分析特性.结果表明: 本方法Pb2+和Cd2+检出限分别为3.5和0.15 μg/L; 富集倍数分别为30和80; RSD分别为1.5%和0.6%(n=9,单个离子浓度为50 μg/L).本方法应用于几种中成药中的痕量铅和镉的同时测定,样品加标回收率在90%～108% 之间, 结果满意.     

新型浓缩柱富集-流动注射光度法测定水中的痕量铜

以二乙氨基二硫代甲酸钠(DDTC)分光光度法为基础,将新型浓缩柱在线富集与流动注射联用以测定水中痕量Cu2+,对浓缩柱的富集、解吸条件以及流动注射参数进行了考察。在最佳条件下,在0.25～45μg/L的范围内,Cu2+的浓度与峰高呈良好线性关系,其线性方程为:y=3.0553ρ+4.2244(R2=0.9984),检出限为0.082μg/L,相对标准偏差(RSD)为3.1%(25μg/L Cu2+,n=10)。利用本方法测定河水中的痕量铜,回收率在95.6%～99.6%之间。     

流动注射在线柱预富集-电感耦合等离子体原子发射光谱测定痕量金属元素

本文报道了流动注射在线柱预富集ICP光谱测定痕量金属的方法,以meso-四(4-磺基苯)卟啉为柱前衍生试剂,硅胶作固定相和盐酸作洗脱液,对痕量金属离子Cu、Mn、Ni、Fe、Pb、Cd进行在线预富集检测。在给定实验条件下,方法的富集倍数为9.3～11.3,检出限和测定的相对标准偏差(n=6)分别在0.32～26.8ng/ml和1.3％～3.0％范围内。方法用于小牛肝和西红柿叶样品分析,结果与参考值吻合。     

流动注射在线置换吸附预富集-火焰原子吸收联用技术测定痕量铅

研究了流动注射在线置换吸附预富集-火焰原子吸收(FAAS)联用技术测定复杂样品中痕量铅的方法。首先使ZnⅡ与二乙基二硫代氨基甲酸钠(DDTC)在线配合形成Zn-DDTC并预先吸附在香烟过滤嘴填充柱上,然后使含PbⅡ的标准溶液或样品溶液流经填充柱与Zn-DDTC发生置换反应而被填充柱富集。被吸附的分析物用乙醇定量洗脱至FAAS进行在线检测。此在线置换吸附预富集过程有效地消除了与DDTC的配合物稳定性较Zn-DDTC弱的共存金属离子的干扰。在样品流速为5.0mL/min和置换吸附预富集90s的条件下,得到铅的吸收信号的增感因子为33,检出限为2.0μg/L。浓度为100μg/L的铅标准溶液11次平行测定的精密度(RSD)为1.2%。本方法已应用于生物样品的分析。     

大体积进样-浓缩柱在线富集-离子色谱法测定水中痕量及超痕量溴酸盐

建立了一种测定水中痕量及超痕量溴酸盐的在线富集大体积进样离子色谱法。采用实验室常备的柱容量较高的Dionex IonPac AG23保护柱作为浓缩柱,连接在定量环处富集溴酸盐。淋洗液自动发生装置在线生成高纯度氢氧化钾淋洗液进行梯度洗脱,抑制电导检测。实验结果表明:溴酸盐质量浓度范围在0.05~51.2 μg/L之间时线性关系良好,相关系数r≥0.9995,方法检出限为0.01 μg/L。与常规进样相比,进样量可高达5 mL,浓缩因子约为240倍。本方法成功应用于市售纯净水中溴酸盐的测定,2个加标水平的回收率在90%~100%之间,RSD(n=6)为2.1%~6.4%。该方法无需前处理,操作简单,准确度和精密度良好。通过大体积进样实现高倍富集,适用于痕量及超痕量溴酸盐的分析。     

共聚物吸附剂富集用ICP-AES法测定痕量铅

建立了马丙共聚物吸附剂富集用ICP-AES法测定痕量Pb2+新方法。马丙共聚物吸附剂对Pb2+具有很高的选择吸附特性,在pH 4.7的HAc-NaAc缓冲溶液中,40 min可达吸附平衡,用0.3 mol/L的HNO3可定量洗脱,富集倍数可达20倍。方法的线性范围为0.002～0.2 mg/L,检出限为0.70μg/L,相对标准偏差为3.1%,加标回收率在92.0%～104.0%之间。     

流动注射在线预分离富集-火焰原子吸收光谱法测定中成药中的痕量镉

应用D-411鳌合树脂作在线分离预富集柱填料,流动注射与原子吸收光谱联用测定中成药中的痕量镉。采样频率28次/h,富集倍数达46倍,线性范围0～0.020mg/L,该方法的检出限(3S,n=10)0.0285μg/L,相对标准偏差5.2%。将该方法用于中成药样品中镉的测定,结果满意。     

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.