电感耦合等离子体原子发射光谱(ICP-AES)法测定锡铅焊料中11种微量元素

根据目前市场上常见锡铅焊料中主元素的特性(锡含量范围0.X%~95%,铅含量范围X%~99%),合理选择了有效的样品前处理方法。参考铸造锡铅焊料牌号及化学成分和仪器工作条件,确定了待测元素的测定范围。应用电感耦合等离子体原子发射光谱法同时测定锡铅焊料中锑、铋、铁、砷、铜、银、锌、铝、镉、磷、金11种元素的含量,方法操作简单。选择了合适的分析谱线,进行了基体元素对待测元素以及各待测元素之间的干扰研究,基体效应小,各待测元素之间基本无干扰,11次独立的测定数据相对标准偏差为1.0%~11.3%,方法的加标回收率为90.2%~105%。完全能满足现实生产中对锡铅焊料杂质元素的测定要求。     

悬浮体进样/氟化电热蒸发(ETV)/ICP-AES直接测定二氧化钛粉末中痕量钇

以聚四氟乙烯(PTFE)悬浮体为氟化剂,悬浮体制样/氟化辅助电热蒸发(ETV)/ICP-AES直接测定TiO₂陶瓷粉末中痕量杂质钇;考察了影响基体和待测元素的蒸发过程的各种因素;对比研究了待测元素和基体的氟化蒸发行为;实现了基体和待测元素的预分离,显着降低了基体效应。本法的检出限为0.26μg/L,相对偏差为3.8%(n=5,c=0.5mg/L).     

新型D-238树脂色层分离-ICP/AES法测定4N光学级La_2O_3中Co、Cr、Cu、Fe、Mn、Ni、Pb和V

本文采用新型D-238树脂,使待测元素与基体La分离。用6mol/L HNO_3解脱非稀土杂质,ICP-AES法同时测定4N光学级La_2O_3中8个痕量非稀土杂质。方法的检出限为0.2～2.8μg/g,相对标准偏差<8%。     

微波消解-ICP-AES法测定拟薄水铝石中11种微量或痕量杂质元素

采用微波消解,ICP-AES法测定了拟薄水铝石中Si,Fe,Na,K,Ca,Mg,Zn,Ti,V,P,Li等11种微量和痕量杂质元素含量。样品用王水溶解,在200℃密闭消解30 min,冷却定容后进行测定。用各元素标准溶液绘制校准曲线,用高纯铝基体匹配校正基体效应。在选定的仪器工作条件下,11种被测杂质元素的检出限范围0.0024~0.42μg/m L,当杂质元素含量大于0.001%时,本法测定值与XRF法和AAS法的测定值相符,不同元素测定值的相对标准偏差(n=10)在0.70%~4.8%之间。     

膜去溶-ICP-MS法测定高纯Eu_2O_3中14种痕量稀土杂质

研究了不需基体分离,膜去溶-ICP-MS法直接测定高纯Eu2O3中的14种痕量稀土杂质的分析方法。讨论了Eu基体产生的多原子离子对被测元素的质谱干扰。使用膜去溶后,待测元素灵敏度提高3倍左右,EuO/Eu产率从去溶前的0.016%降低为0.0007%。建立了Tm的数学校正方程,通过膜去溶结合数学校正可将Eu基体对Tm干扰完全消除。14种稀土杂质的检出限和(∑RE)为70 ng/L,测定下限和(∑RE)为0.54μg/g。对6N高纯Eu2O3样品进行了分析,样品回收率为96%~109%,RSD小于10%。所建立的方法对Eu2O3标准样品的测定结果与国家标准方法测定结果相一致。     

微波消解-石墨炉原子吸收光谱法测定纳米二氧化钛中痕量砷

建立了微波消解-石墨炉原子吸收光谱法（GF-AAS）测定纳米二氧化钛中痕量杂质元素砷的分析方法。采用由一定浓度和比例的氢氟酸、硝酸组成的混合试剂,结合应用高压密闭微波加热技术快速完全消解纳米二氧化钛样品,优选了最佳微波加热控制程序,不仅解决了二氧化钛难消解和待测元素砷高温消解过程中易挥发损失等难点,而且检测溶液酸度低,避免对GF-AAS石墨管的侵蚀。并且,通过基体效应影响实验,优化选择了石墨管类型、石墨炉升温原子化控制程序以及原子吸收光谱仪检测参数,消除热稳定性强的二氧化钛基体对测定易挥发痕量元素砷的影响。方法检出限为0.02μg/L,加标回收率为93.0%~106.0%,相对标准偏差9.4%,与ICP-MS检测方法结果对照一致。     

共沉淀分离-氢化物发生-原子荧光光谱法测定高纯偏钨酸铵中痕量铋

提出了以氢氧化镧为共沉淀剂,对高纯偏钨酸铵中痕量杂质元素铋进行共沉淀分离富集后以HG-AFS进行测定的方法。在强碱性环境中进行两次共沉淀,能使铋元素定量分离回收,偏钨酸铵残留量降至很低水平。选择了适宜的反应条件以及仪器的最佳工作条件,考察了钨基体对被测元素的干扰。铋的检出限0.020 ng/mL,测定下限0.012μg/g,相对标准偏差4.6%,回收率在92.8%~108.4%之间,方法适用于高纯偏钨酸铵中痕量铋的测定。     

电感耦合等离子体发射光谱法测定二硼化锆中26种杂质

建立微波消解样品,电感耦合等离子体发射光谱法测定二硼化锆中26种杂质元素含量的方法。根据二硼化锆的化学组成对杂质检测的影响,确定了各元素最佳分析线;通过考察不同浓度的锆基体对待测元素的影响来确定最佳锆基体浓度;通过萃取法分离硼元素,消除硼对杂质检测的干扰;采用基体匹配法、多谱拟和技术消除了锆基体的干扰。在选定的仪器工作条件下,各待测元素的质量浓度与信号强度成良好的线性关系,线性相关系数均大于0.999。测定结果的相对标准偏差不大于6%(n=11),样品加标回收率为94%~101%。该方法操作简便,测定结果准确,可用于二硼化锆中26种杂质元素的测定。     

电感耦合等离子体质谱(ICP-MS)法测定高纯砷中痕量磷和硒

通过对样品前处理方式、内标元素及质量数的选择、仪器检测模式等方面进行优化,采用串联四级杆电感耦合等离子体质谱仪直接测定高纯砷中痕量的磷和硒.实验室使用电子级盐酸、硝酸配制王水直接溶解样品,在不除基体的情况下,以铑作为内标补偿校正砷基体的抑制效应,在调试好的仪器上进行测定磷、硒含量.磷、硒的测定结果相对标准偏差(RSD)...     

石墨炉原子吸收法测定高纯硒中痕量铁

研究了石墨炉原子吸收直接进样法和石墨炉内富集法测定高纯硒中痕量铁的条件,建立了石墨炉原子吸收法直接测定高纯硒中痕量铁的分析方法.直接进样法的检出限为0.008 μg/g,石墨炉内富集法的检出限为0.004 μg/g,相对标准偏差分别为:5.2%和4.6%,两种方法检测样品结果基本一致.测定含铁0.3 μg/g的高纯硒,测定值的RSD为4.6～5.2%.     

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.