X射线荧光光谱铝环-双层压片法测定土壤中常量和微量元素

本文提出用铝环-双层压片法制片,经验系数法校正吸收-增强效应,对少量土壤样品中的常量和微量元素进行了定量测定。取样量为500 mg,制样与测量精确度好于5%,用本法对标样的分析表明,分析值与推荐值基本一致,本法具有简单、快速、成本低的特点,适用于少量样品的分析。     

透明胶纸制样法X—射线荧光光谱测定蒙脱石中的化学元素

本文提出以透明胶纸作为少量粉末样品的支持物来制备样片,采用透空照射法,在日本理学3080E3型X-射线荧光光谱仪上实现了蒙脱石中化学元素的定量测定。本法样品实际用量约10mg,制样与测量精度较好,标样及样品的分析结果与推荐值及AAS法分析结果基本一致,方法具有简单、快速、准确和成本低的特点,适用于少量样品和单矿物的分析。     

矿石中铀的精密电位滴定

本文提出的精密电位滴定法,采用HF-HNO_3-HClO_4溶矿,不过滤、不分离,缩小了滴定液的体积;同时还重视了电极对滴定精度的影响,提出了有效的处理方法;在确定终点所消耗的NH_4VO_3体积时,采用二次电位差分法进行精确计算,提高了方法的精密度。本法对铀矿石标准样品和铀矿石样品的分析,其准确度和精密度均小于±1.5％。操作步骤 1.样品处理:准确称取矿样1.000～2.000g于100ml聚四氟乙烯烧杯中,用少量水湿润,加5～     

大洋底多金属结核样品中主、次、微量元素的X射线荧光光谱测定

制定了一个用X射线荧光光谱法测定大洋底多金属结核样品中主、次、微量元素的分析方法。样品用石墨坩埚、混合熔剂低倍稀释熔融,用人工标样作为校准标准。计算了COLA方程的理论α系数,用于校正28个分析元素的吸收-增强效应。本法测定结果与化学法结果相吻合。     

能散X射线荧光光谱法测定烧结预配料中铁硅钙

目前对用XRF法分析样品化学成分研究很多，但大部分是运用进口波散型荧光仪WDXRF进行分析。而使用国产能散型荧光仪EDXRF分析样品化学成分研究很少。本文用国产能谱仪用XRF法对烧结用预配料中铁、硅、钙进行分析，运用了有关数学校正方法，绘制了标准曲线。经试验本法精密度高、速度快，能满足生产控制分析需要。     

ICP—AES法测定化探样品中8种元素

本法用HF+HClO_4+HNO_3混合酸溶样,样品溶后不去溶、不分离,清液直接引入ICP光源摄谱。标液中加入模拟基体元素与样品溶液匹配来消除分析误差。检测限和精度均能满足部颁化探分析要求。     

TBP萃淋树酯反相色层分离ICP—AEP法测定岩石中的微量金

本文介绍采用TBP萃淋树酯萃取分离结合仪器分析测定岩石中微量金的方法。方法包括三部分:样品分解、分离富集、及用ICPQ—100光量计测定。本法样品称量一般为10—20g,用王水分解,经过抽滤,将滤液体积控制在150ml左右,使酸度保持为5—10%。通过萃淋树酯交换柱分离富集,并除去可能产生干扰谱线的元素。测出金的下限为0.10克/吨,经与金的管理样结果对照,本法的准确度与检出限能满足地质勘探样品金测定的要求。     

原子吸收分光光度法测定生物样品中的游离脂肪酸

本文研究了用原子吸收分光光度法间接测定生物样品中游离脂肪酸(FFA)的方法,用氯仿-正己烷-甲醇混合液萃取样品中FFA,用铜溶液与FFA形成“铜皂”,进入有机相,未反应的Cu~(2+)进入水相,用原子吸收法测定有机相中铜,间接求得游离脂肪酸含量。本法线性范围为10～100nmol,对血浆测定结果的相对标准偏差为<6.59％,回收率为96％～102％。本法的测定结果与比色法的结果基本一致。     

一氧化二氮-乙炔火焰原子吸收法直接快速测定钢铁中铝

用自制高效玻璃雾化器代替WYX-401型原子吸收分光光度计的雾化器,并相应改动其预混合雾室的结构。试验确定了火焰原子吸收测定铝的最佳条件。铝的特征浓度值达到0.59微克/毫升/1％吸收;检出限达到0.18微克/毫升.考察了盐酸、硝酸、过氯酸和各种共存元素对铝的干扰。拟定了钢铁中酸溶铝的直接快速火焰原子吸收测定方法。本法测定下限为0.005％。以本法分析硅钢、低合金钢、工业纯铁标准样品和实际生产控制分析样品得到的结果与标准样品的标准值或比色法测定的结果相符合。方法快速、简便、灵敏、可靠。     

关于微量硅的吸咐沉淀分离-分光光度法的研究及其应用之一:钢铁中硅的测定

硅与氢氧化铍共沉淀进行分离,然后以“硅钼兰”显色进行测定。锡、磷和砷一起沉淀,显色时加入酒石酸和草酸消除其干扰。少量三价铬的颜色在波长815毫微米处无吸收,不干扰硅的测定。本法可测一般钢铁中大于0.002％的硅和高合金钢中大于0.005％的硅。对近20种钢铁、纯铁、纯镍等标准样品进行过对照分析,都得到同标准值一致的结果。     

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.     

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.     

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.     

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.