石墨炉原子吸收光谱法测定磷矿石中微量铅

研究了石墨炉原子吸收光谱法测定磷矿石中微量铅，探讨了熔样过程，基体效应，共存元素及载气流速等干扰，并进行了干扰抑制试验，提出了最优方式对磷矿石中微量铅进行测定，回收率为90．5％～107．0％。     

微波消解-原子吸收光谱法测定槐花和大黄中微量元素

采用微波消解-火焰原子吸收光谱法和石墨炉原子吸收光谱法测定了中药槐花和大黄中铜、铁、锌、镉、铬和铅。研究了槐花和大黄的微波消解试剂和消解条件。在原子吸收光谱测定的最佳条件下测定槐花和大黄中铜、铁、锌、镉、铬和铅。方法的回收率在89．2％～112．0％之间。     

原子吸收光谱法测定铅的进展

对近年来国内原子吸收光谱法测定铅的进展进行了评述，内容包括火焰原子吸收光谱法、石墨炉原子吸收光谱法和氢化物发生原子吸收光谱法。     

氢化物发生-原子吸收光谱法测定食盐中微量铅

食盐中铅测定采用萃取-原子吸收光谱法，方法使用有机试剂，操作也复杂。采用石墨炉原子吸收光谱法直接测定，氯化钠干扰很大。本文提出氢化物发生-原子吸收光谱法测定食盐中铅。采用WHG-102A2型流动注射氢化物发生器与原子吸收光谱仪配合，载气压力作为自动化能源，流动注射方     

土壤中铅的分析方法比对

对不同的样品消解方法及电感耦合等离子体质谱、电感耦合等离子体原子发射光谱、石墨炉原子吸收光谱法测定土壤中铅的测定结果进行比对。采用电热板、微波及水浴3种加热方式,选择硝酸、氢氟酸、双氧水、王水、高氯酸、盐酸的不同组合进行土壤样品消解,通过分析测定值的精密度和准确度,考察消解体系对电感耦合等离子体质谱、电感耦合等离子体发射光谱、石墨炉原子吸收光谱法测定结果的影响。结果表明采用电感耦合等离子体质谱法测定土壤中的铅,最适宜的消解体系是硝酸-氢氟酸-高氯酸(微波加热),采用电感耦合等离子体原子发射光谱法测定最适宜的消解体系是硝酸(电热板加热),采用石墨炉原子吸收光谱法测定最适宜的消解体系是硝酸-盐酸-高氯酸(微波加热)。电感耦合等离子体质谱法的精密度和准确度优于另外两种方法。     

石墨炉原子吸收光谱法测定尿中铅含量

近年我国铅污染事件呈高发态势,严重威胁群众健康。铅能引起几乎所有器官系统的功能紊乱,尤其是血液和神经系统,尿铅水平是评价体内铅含量的重要指标,石墨炉原子吸收光谱法测定尿铅具有灵敏、快速和准确的特点,本工作在卫生部推荐方法WS/T 18-1996尿铅的石墨炉原子吸收光谱法     

电感耦合等离子体原子发射光谱法(ICP-OES)与石墨炉原子吸收光谱法测定饮用水中重金属元素的比较

通过对比电感耦合等离子体原子发射光谱法(ICP-OES)与石墨炉原子吸收光谱法(AAS)测定水中重金属的检出限、重复性、加标回收率等实验,验证两种方法的准确性,从而为饮用水中重金属的测定提供可靠的方法。结果表明,石墨炉原子吸收光谱法测定饮用水中砷、镉、铬、铅、汞、硒的检出限均低于ICP-OES法,但ICP-OES法测定线性范围宽,重复性和加标回收率均优于石墨炉原子吸收光谱法,分析速度快,操作便捷,结果满意,是目前饮用水中重金属测定非常可靠的方法。     

石墨炉原子吸收法测定豆豉中铅和镉

豆豉样品经微波消解后,采用石墨炉原子吸收光谱法快速测定铅、镉。实验优化了石墨炉原子吸收光谱法的测定条件。以磷酸为基体改进剂可提高灰化温度,消除样品中的氯化钠等复杂基体的干扰。该法铅、镉的回收率分别为95.0％、94.6％,精密度（RSD）分别为8.7％和5.1％。结果表明豆豉中铅、镉含量较低。本方法简便、快速、准确,适合于实际的分析工作。     

石墨炉原子吸收光谱法测定蘑菇中的镉、铅

采用石墨炉原子吸收光谱法测定蘑菇中的镉、铅，以磷酸二氢铵和硝酸镁作混合基体改进剂，提高了测定的灰化温度，消除了基体干扰。方法简便，快速，准确度高。镉和铅的相对标准偏差为3．7％-6．0％和7．3％-7．9％；回收率为98％-106％和98％-104％；检出限为0．009μg/g和0．032μg/g。     

石墨炉原子吸收光谱法测定硒的条件研究

硒是人类和动物的必需微量营养元素之一，过量摄入则会引起急性或慢性中毒。近几十年来，人们对硒的测定方法进行了很多有益的探讨，应用较多的有原子荧光法、氢化物发生原子吸收光谱法、石墨炉原子吸收光谱法和中子活化法等，其中石墨炉原子吸收光谱法测定硒具有操作简便、分析速度快、灵敏度高等优点而得到了较快的发展。但由于硒是易挥发元素，     

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.     

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.     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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.     

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.