聚氨酯泡沫塑料吸附-电感耦合等离子体质谱(ICP-MS)法测定地球化学样品中的痕量金

探讨了聚氨酯泡沫塑料的预处理、样品浓度、水洗条件、基体元素对金吸附率的影响等因素。结果表明,用泡沫塑料吸附含金量为5 ng~500μg的溶液,吸附率均在90%以上。影响聚氨酯泡沫塑料吸附率的重要条件是振荡前要用水充分浸透,水洗基体元素,矿渣宜在酸性环境下进行。铁、钛等离子可以提高吸附率,钠、钙、锌、矿渣等影响不显著,铝离子有微弱的抑制作用。ICP-MS的灵敏度与介质的雾化率有一定的相关性,应当使用硫脲介质的工作溶液作工作曲线,内标元素可用103Rh或185Re,但是对于高含量W样品,只能使用103Rh作内标。用金矿石国家标准物质做精密度与准确度验证,测定值与标准值无显著差异,相对标准偏差(RSD)均小于10%,精密度能满足地球化学样品中痕量金的分析要求。     

石墨炉原子吸收光谱法测定化探样品中痕量金

化探样品经650 ℃高温灼烧1.5 h后,用HNO3-HCl(1+1)溶解.取一块聚氨酯泡沫塑料(3 cm×2 cm×1 cm)吸附富集样品溶液中痕量金,通过将上述富集金的聚氨酯泡沫塑料置于硫脲溶液中沸水浴保持20 min,使金被释放出来,所得溶液供石墨炉原子吸收光谱仪测定.对石墨炉原子化条件和基体改进剂抗坏血酸的用量进行了试验并予以优化.方法的检出限(3S/N)为0.06 ng·g-1.方法用于测定国家标准样品,测得值的相对标准偏差(n=11)小于6.0%.     

聚氨酯泡沫塑料富集-电感耦合等离子体发射光谱法测定地质样品中的金

建立聚氨酯泡沫塑料富集–电感耦合等离子体发射光谱法测定地质样品中金的方法。泡沫塑料预处理:用5%NaOH溶液浸泡60 min,再用10%HCl溶液浸泡120 min。金矿样品用王水溶解,再用预处理的泡沫塑料吸附其中的金,灰化后用王水溶解,在选定的仪器工作条件下进行测定。金的质量浓度在0.00~20.00μg/mL范围内与光谱强度呈良好的线性关系,相关系数为0.999 5,方法的检出限为9.9 ng/mL。测定结果的相对标准偏差为1.15%~3.99%(n=10),用该法测定金矿石国家标准物质,测定值与标准值基本一致。该方法准确、可靠,能够满足地质样品中金的分析测试要求。     

聚氨酯泡沫塑料富集-电感耦合等离子体质谱法测定地质样品中痕量铂和钯

以聚氨酯泡沫塑料为吸附剂于静态操作条件下,对痕量铂和钯的选择性吸附分离的方法进行了研究。试验表明,泡塑在3.6～4.8mol·L-1HCl溶液与40g·L-1SnCl2溶液构成的吸附介质中,对铂、钯的吸附性能很好,饱和吸附容量为12.90～19.24mg·g-1,钯平均吸附率为95.81%,铂平均吸附率为98.35%,吸附到泡塑中的铂、钯可用灰化法回收,富集倍数可达100倍。结合电感耦合等离子体质谱法,可用于地质样品中痕量铂、钯的富集分离和测定。方法经标准样品分析验证,铂、钯的测定结果与推荐值吻合,标样及样品分析的RSD≤6.5%(n=12)。     

电感耦合等离子体质谱(ICP-MS)法测定地质样品中的金

建立了王水溶解-聚氨酯泡沫塑料吸附-电感耦合等离子体质谱(ICP-MS)法测定地质样品中的金。探讨了振荡时间对回收率的影响,最终确定振荡时间为1h。在优化条件下,方法的相对标准偏差(RSD,n=12)在4.2%~9.0%,加标回收率在92.00%~114.6%,方法检出限为0.11ng/g。方法操作简单,测定精密度高,检出限低,满足大批量地质样品的分析需要。     

聚氨酯泡沫塑料富集-ICP-MS测定化探样品中微量金

试样经王水分解后,在铁盐作用下,用经过酸、碱、无水乙醇处理后的聚氨酯泡沫塑料振荡吸附金,硫脲快速解脱,待溶液澄清后用ICP-MS进行测定。结果表明,本方法的检出限为0.36 ng/g、精密度(RSD,n=10)为7.7%,回收率为80%~119%,经国家标准物质的分析验证,测得的结果与标准值符合。     

快速石墨炉原子吸收光谱法测定尿铊

尿样用硫酸-硝酸混合酸消化,并用溴水将溶液中铊(Ⅰ)氧化至铊(Ⅲ),用盐酸(1 4)介质使铊(Ⅲ)以络阴离子Tl(Cl)4-状态存在。用聚氨酯泡沫塑料吸附铊(Ⅲ),从而与尿液分离,且达到消除尿液中无机盐的干扰和一定的富集效果。将聚氨酯泡沫塑料取出并洗净后置于沸水中使铊(Ⅲ)从泡沫塑料上解吸,所得溶液供石墨炉原子吸收光谱法(GF-AAS)测定。在方法中不加任何基体改进剂且在石墨平台升温程序中省略了灰化步骤,使测定达到快速的要求。方法的测定限达到0.1μg.L-1,测得回收率在91%~97%之间。     

泡沫塑料富集-火焰原子吸收光谱法测定金矿石中金

采用聚氨酯泡塑富集硫脲洗脱-火焰原子吸收光谱法测定金矿石中金。对样品称样量、硫脲洗脱时间、磷酸三丁酯的吸附效果和铁元素的干扰等工作条件进行了优化,解决了泡沫塑料吸附效率低和铁元素的干扰等技术性难题,提高了分析结果的精密度和准确度,弥补了传统的泡沫塑料富集-火焰原子吸收光谱法测定金矿石中金量的不足,方法检出限为0.06 μg/g,测定范围为 0.2 μg/g～100 μg/g,测定结果与标准值符合性较好,无显著性差异,精密度(RSD, n = 9) 小于2%。方法具有快速、简便、实用等优点,分析误差满足常规化学分析法的要求,能满足金矿石中金量的快速、准确测定。     

双孔石墨管原子吸收法测定化探样品中的痕量金

建立了双孔石墨管原子吸收法测定化探样品中痕量金的方法。以王水溶解样品,泡沫塑料吸附,10 g/L的硫脲溶液解脱,2%抗坏血酸作为基体改进剂,用双孔石墨管原子吸收法测定化探样品中的痕量金。该方法仪器分析时间由65 s缩短到32 s,提高了工作效率,方法标准曲线线性相关系数为0.999 8,检出限为0.045 ng/g,测定结果的相对标准偏差为4.1%~6.9%(n=7),标准样品测定值与推荐值的相对偏差小于3.24%。该法适合批量化探样品中金的测定。     

TNA负载聚氨酯泡塑富集ICP-MS测定地球化学样品中痕量金、铂、钯

研究提出了负载聚氨酯泡沫塑料富集ICP—MS测定地球化学样品中的金、铂、钯的方法,研究了样品经灼烧、王水溶样后,负载泡沫塑料吸附条件、干扰的消除、仪器的最佳化、内标元素的选择等。在本工作的实验条件下获得的方法检出限分别为Au：0．12ng／g,Pt：0．10ng／g,Pd：0．08ng／g。本法测定了国家一级地球化学标准物质中的痕量Au,Pt,Pd,测定值与标准值相吻合。     

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.     

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.     

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.