Teflon AF 2400管冷蒸气发生-原子荧光法分析烟草中的痕量汞

采用具有高气体渗透性和紫外光透过性的无定形聚四氟乙烯管(Teflon AF-2400)作为蒸气发生原子荧光系统的气液分离器和检测池,建立了微型化汞蒸气发生原子荧光检测系统。考察了Teflon AF-2400管长度、还原剂种类和浓度、酸介质种类和浓度、进样流速以及氩气流速对测量体系的影响。在优化实验条件下,该方法的线性范围为0.07~10μg/L(r=0.998 0),检出限为0.02μg/L,相对标准偏差(n=11)为3.3%。该系统体积小、样品消耗少、灵敏度高。方法已成功应用于卷烟样品中汞含量的检测,回收率为97%~102%。     

紫外光诱导化学蒸气发生-氩/氢火焰原子荧光光谱法测定丹参中硒

以紫外光诱导化学蒸气发生装置作为原子荧光光谱仪的进样系统,建立了光化学蒸气发生原子荧光光谱法测定中药材丹参中总硒含量的分析方法。研究了试剂浓度、光化学蒸气反应管等因素对硒化学蒸气发生效率的影响。仪器对硒的检出限为6.60 ng/mL,精密度(RSD)为0.6%(n=10),回收率为98%～107%。     

蒸气发生火焰原子吸收法测定面粉中的铜

用自制的蒸气发生装置,在强还原剂存在下,对铜蒸气的生成进行了详细研究,并通过该装置测定非蒸气发生元素镁和在络合剂掩蔽下测铜两种不同的方法进行了验证。对酸的种类及浓度、NaBH4溶液流速及浓度、反应管道长度的影响等实验参数和干扰情况进行了研究。用该方法测定了面粉中铜的质量分数,检出限为6μg L。     

原子荧光光谱进样技术的研究进展

原子荧光光谱已成为检测金属或类金属的重要手段,其仪器进样方式与所用原子化器类型直接相关。根据进样原理的不同,综述了原子荧光光谱仪器的直接进样、喷雾进样、化学蒸气发生进样和电热蒸发进样4种进样技术,详细介绍了原子荧光光谱各进样技术特别是化学蒸气发生进样和电热蒸发进样的发展历程、原理及优缺点,展望了原子荧光仪器进样技术的发展前景。引用文献75篇。     

原子荧光光谱技术在我国发展及标准化应用现状

简单介绍了原子荧光光谱技术的建立及其在国内的发展历程,重点介绍了蒸气发生-原子荧光光谱(VG-AFS)仪在我国的技术研究、仪器研制及应用;详细总结了蒸气发生-原子荧光光谱(VG-AFS)法在我国标准化方面的研究.我国在多通道原子荧光光谱仪、原子荧光形态分析仪等关键技术及其应用等方面取得了开创性的研究成果,并形成了一系列...     

低温等离子体原子荧光光谱法直接测定固体样品中的汞

建立了低温等离子体(LTP)与原子荧光光谱仪(AFS)联用直接检测ABS固体样品中Hg的方法.实验采用介质阻挡放电(DBD)方式产生低温等离子体,剥蚀固体样品后产生的元素蒸气引入到原子荧光光谱仪进行检测.优化的实验条件为:DBD外接电源的放电功率为16～18 W,放电气体流速为400 mL/min;采样距离为1～5 mm;原子荧光光谱仪的原子化器高度为10 mm.本系统测定Hg的检出限为0.91 mg/kg,线性范围为91.5～1096 mg/kg;精密度(RSD,n=7)为1.9％～2.3％,并对标准样品以及实际样品进行测定,测定结果与标准值与ICPMS及CVG-AFS一致,表明本方法可作为直接检测固体样品的新型元素分析技术.     

光化学蒸气发生方法用于水样中汞的可视化检测

汞与碘化亚铜的络合显色反应已被广泛应用于汞的可视化检测。然而,样品中高盐、强酸或强碱性的复杂基质对碘化亚铜及络合物的稳定性影响较大,可视化测定受到了严重干扰。光化学蒸气发生是一种绿色、高效的样品引入技术,可实现待测离子与样品基质的有效分离,并且在蒸气发生过程中不需要添加有毒、强还原性试剂。因此,本实验建立了一种光化学蒸气发生和自制碘化亚铜试纸结合用于可视化检测水样中汞的方法,对反应时间、低分子量有机酸浓度等条件进行了考察。在最优的条件下实现了1 ng·mL^-1~1μg·mL^-1浓度范围内水样中汞的可视化半定量分析,并通过原子荧光光谱法对分析结果进行了验证。     

离子液体双水相萃取-蒸气发生原子荧光法测定痕量镉

研究了离子液体1-异戊基-3-甲基咪唑溴代盐-K2HPO4-水双水相体系对镉-双硫腙络合物的萃取性能,建立了测定痕量镉的蒸气发生-原子荧光光谱法.经离子液体双水相萃取后,在离子液体相中的镉-双硫腙络合物经酸化后可直接与还原剂(NaBH4)混合进行蒸气发生反应,并经气液分离后将蒸气引入原子化器中进行原子荧光检测,离子液体的存在不影响蒸气发生过程.考察了双水相系统的组成以及相关实验条件对镉-双硫腙络合物萃取的影响.在最佳实验条件下,样品体积为1 mL时,测定痕量镉的线性范围为0.25～5.0 μg/L,检出限为0.07 μg/L; 相对标准偏差为3.4%(n=9, 2.0 μg/L Cd2+).用国家标准物质GBW08608(水中镉、铬、铜、镍、铅、锌成分分析标准物质)验证了方法的准确性,并对实际水样中的痕量镉进行了测定.     

中国30多年来原子荧光光谱仪器的发展与应用

主要简述了原子荧光光谱仪器的发展历史,对我国30多年来原子荧光商品仪器在激发光源、石英管原子化器、蒸气发生反应系统等方面的发展作了详细论述,还就近年来新开发的原子荧光光谱仪器在多元素同时测定、多功能化、—机多用、形态分析等方面的技术发展和应用进行了全面阐述,并对原子荧光光谱分析领域的发展作出了展望。     

电化学冷蒸气发生-原子荧光光谱法测定人发中的痕量汞

采用自制的电化学流通池作为汞蒸气发生器,以玻碳为阴极材料,结合原子荧光光谱法,在断续流动条件下,建立了电化学冷蒸气发生法-原子荧光光谱联用技术(ECVG-AFS)对汞的分析方法.在优化的实验条件下,汞在0～5.0μg/L范围内荧光强度与浓度呈良好的线性关系,汞的检出限为1.2 ng/L.对1μg/L Hg测定的相对标准偏差为1.8%(n=11).可用于人发标准样品中汞的测定.     

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.     

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.