电感耦合等离子体原子发射光谱法(ICP-AES)测定无定形硼粉中的镁

提出了使用电感耦合等离子体原子发射光谱法(ICP-AES)测定Mg元素的方法。采用硝酸、盐酸溶解样品,用硝酸和盐酸的混合酸作为测定介质,在选定的仪器条件下直接测定Mg元素的检出限为0.0044μg/mL,相对标准偏差RSD(n=6)为0.49%～0.60%,样品加标回收率在94.0%～102.0%之间。经对比试验证明,电感耦合等离子体原子发射光谱法(ICP-AES)测定无定形硼粉中Mg的测定值与美国军用标准重量法测定值一致。     

电感耦合等离子体原子发射光谱法(ICP-AES)测定红土镍矿中的Cd、Co、Cu、Mg、Mn、Ni、Pb、Zn、Ca9种元素

提出了使用电感耦合等离子体-原子发射光谱法同时测定红土镍矿中Cd、Co、Cu、Mg、Mn、Ni、Pb、Zn、Ca的分析方法.采用盐酸、硝酸和氢氟酸处理样品,以盐酸作为测定介质,在选定的仪器工作条件下直接测定.各元素的测定检出限为0.0001～0.0033μg/mL,相对标准偏差(RSD,n=6)为0.15%～1.89%...     

电感耦合等离子体原子发射光谱(ICP-AES)法测定铜原矿和尾矿中的杂质元素

采用盐酸+硝酸+氢氟酸+高氯酸溶解试样,通过样品酸浓度条件、分解条件、共存元素干扰等实验,建立了电感耦合等离子体原子发射光谱法测定铜原矿和尾矿中的铜、铅、锌、镍、钴、镉、镁和锰含量的方法.测定范围:ω(Cu):0.010％～2.50％,ω(Pb):0.005％～1.00％,ω(Zn):0.005％～1.50％,ω(Ni):0.005％～0.05％,ω(Co):0.005％～0.05％,ω(Cd):0.005％～0.015％,ω,(Mg):0.010％～8.00％,ω(Mn):0.005％～0.50％.经加标回收实验,各元素的加标回收率为86％～103％(n=3),方法准确、可靠,适用于铜原矿和尾矿的铜、铅、锌、镍、钴、镉、镁和锰量的同时测定.     

不同混合酸消解样品对电感耦合等离子体原子发射光谱法测定土壤中重金属含量的影响

为探究不同混合酸对电感耦合等离子体原子发射光谱法测定土壤中重金属元素(铜、锌、铅、镍和铬)的影响,对土壤进行多晶衍射分析,采用硝酸-高氯酸、盐酸-硝酸、盐酸-硝酸-氢氟酸-高氯酸、盐酸-硝酸-氢氟酸混合酸对4种不同类型土壤(黑钙土、褐土、棕壤、红壤)进行了分析。结果表明:该4种混合酸对标准样品的测定都具有较高的准确性与精确性;不同的混合酸的对不同类型土壤中重金属元素的测定具有一定的影响,其中对铬的影响最大;完全消解体系(盐酸-硝酸-氢氟酸-高氯酸、盐酸-硝酸-氢氟酸混合酸)的测定结果不同程度地高于不完全消解体系(硝酸-高氯酸、盐酸-硝酸混合酸)的结果。所以对于土壤重金属元素的测定,混合酸需要针对土壤类型,重金属元素种类等因素进行选择。     

电感耦合等离子体质谱法同时测定植物类新食品原料中14种无机元素北大核心CSCD

0.500 0g样品经硝酸3mL、过氧化氢2mL消解后,采用电感耦合等离子体质谱法同时测定样品溶液中Na、Mg、Ca、Al、Cu、Zn、Fe、Mn、Se、Pb、Cd、As、Hg和Cr的含量。采用0.5%(体积分数)硝酸的基体酸度增强分析元素的信号强度;在两次测试之间用100μg·L-1 Au-5%(体积分数)硝酸溶液清洗仪器,降低Hg的吸附效应;利用甲烷碰撞动态反应池技术消除了分析过程中的质谱干扰,选择Sc、Y、In、Bi为内标元素校正基体效应。14种元素的质量浓度在一定范围内与信号强度呈线性关系,检出限(3s)在0.003~0.039μg·L^(-1)之间。方法用于分析国家标准物质GBW 10027,各元素测定值与认定值相符,测定值的相对标准偏差(n=6)在1.6%~14%之间。     

电感耦合等离子体质谱(ICP-MS)法测定铜铅锌矿中稀土元素

铜铅锌矿石样品中加入硝酸、盐酸、氢氟酸、高氯酸,在封闭消解杯中处理后,再加硫酸冒烟,盐酸提取,稀释后用电感耦合等离子体质谱(ICP-MS)法测定其中的稀土元素,并用铑和铱作内标元素补偿基体效应和灵敏度漂移。根据铜铅锌矿石标准参考物质(GBW07233～GBW07237)的分析结果评价方法的准确度和精密度,对标准物质的测定值与标准值基本一致,方法相对标准偏差(RSD)为1.2%～7.6%,符合地质样品分析规范要求。方法检出限为0.001～0.011μg/g。     

电感耦合等离子体质谱法同时测定植物类新食品原料中14种无机元素

0.500 0g样品经硝酸3mL、过氧化氢2mL消解后,采用电感耦合等离子体质谱法同时测定样品溶液中Na、Mg、Ca、Al、Cu、Zn、Fe、Mn、Se、Pb、Cd、As、Hg和Cr的含量。采用0.5%(体积分数)硝酸的基体酸度增强分析元素的信号强度;在两次测试之间用100μg·L-1 Au-5%(体积分数)硝酸溶液清洗仪器,降低Hg的吸附效应;利用甲烷碰撞动态反应池技术消除了分析过程中的质谱干扰,选择Sc、Y、In、Bi为内标元素校正基体效应。14种元素的质量浓度在一定范围内与信号强度呈线性关系,检出限(3s)在0.003~0.039μg·L~(-1)之间。方法用于分析国家标准物质GBW 10027,各元素测定值与认定值相符,测定值的相对标准偏差(n=6)在1.6%~14%之间。     

微波消解-电感耦合等离子体质谱法测定土壤中10种重金属元素

利用硝酸、盐酸、氢氟酸混合液和微波消解仪密闭消解样品，建立了一种微波消解-电感耦合等离子体质谱（ICP-MS）法同时测定土壤中铜、铅、锌、锰、钒、铬、镉、镍、锡、铊10种重金属的分析方法。取0.100 0 g土壤样品于消解罐中，采用4 mL硝酸+1 mL盐酸+1 mL氢氟酸消解体系按照设定程序进行微波消解，冷却，定容后利用电感耦合等离子体质谱法进行。结果表明，以铑元素作为内标，10种重金属元素在一定的质量浓度范围内与其信号强度呈线性关系，线性相关系数均不小于0.999 8，检出限为0.010～0.92 mg/kg。对3种标准物质进行测定，测定值的相对标准偏差为2.89%～7.72%(n=10)，相对偏差为-5.95%～4.11%。该方法分析流程简单，工作效率高，检出限低，适合大批量土壤样品的多元素同时分析。     

电感耦合等离子体发射光谱(ICP-OES)法同时测定活性炭中铝、钴、镉、铜、铁、镁、锰、钠、磷、硫10种元素

提出了使用ICP-OES同时测定活性炭中Al、Co、Cr、Cu、Fe、Mg、Mn、Na、P和S的分析方法。采用高氯酸和硝酸处理样品,以硝酸作为测定介质,在选定的仪器工作条件下直接测定。各元素的测定检出限为0.002～0.012μg/mL,相对标准偏差(RSD,n=6)为0.32%～1.83%。对样品进行加标回收试验,回收率在92.1%～108.4%之间。实验表明:方法不仅具有较高的灵敏度和较低的检出限,而且快速、准确,能够满足活性炭和以活性炭为载体的催化剂杂质元素分析的要求。     

电感耦合等离子体原子发射光谱法测定石墨烯增强铝合金中13种元素

建立测定石墨烯增强铝合金中Mg、Cu、Si、Mn、Zr、Zn、Ga、Ni、Cr、Ti、Fe、V、Be的电感耦合等离子体原子发射光谱方法。称取0.200 0 g样品，用盐酸溶液和硝酸溶液溶解，定容后用中速滤纸过滤掉黑色残留物，在优化的仪器工作条件下对基体匹配的混合标准工作溶液进行测定。13种元素的质量分数在0%～0.100%范围内与光谱强度具有良好的线性关系，相关系数均不小于0.993，检出限为0.000 01%～0.015%。测定结果的相对标准偏差为1.76%～10.21%(n=6)，样品加标回收率为95.0%～110.0%。该方法适用于石墨烯增强铝合金中多种元素的测定。     

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%.     

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.     

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.