脂胺泡沫塑料富集火焰原子吸收法测定化探样品中痕量镉的研究

镉在地壳岩石中和土壤中的平均含量分别为0.2和0.5ppm,区域化探扫面和成矿区(带)样品的分析结果要求为0.2ppm。而等离子光谱法测定化探样品中低温易挥发元素镉尚存在一定困难;目前多采用电热石墨炉原子吸收法测定,但该法的精密度较差,且工效低;溶剂萃取火焰原子吸收测定镉可以满足化探要求,但因有机溶剂易挥发和产生毒害,所以在日常生产分析上难以推广。因此研究一个快速、准确且无环境污染的富集化探样品中的痕量镉,与火焰原子吸收相结合的测定方法是一项具有实际意义的工作。     

微波消解-石墨炉原子吸收法快速检测葡萄酒中铅、镉

葡萄酒样品采用电热消解仪140 ℃预消解30 min后,经过微波消解仪处理,消解条件为:V(HNO3)∶V(H2O2)＝7∶1,180 ℃,800 W,10 min,然后采用石墨炉原子吸收法对其中铅、镉含量进行测定.研究表明,将本法应用于葡萄酒样品中Pb、Cd的测定,结果令人满意,Pb和Cd的检测限分别为3.0 μg/L和0.5 μg/L,RSD均小于5.0%,回收率Pb 74.5%～101.5%,77.3%～104.3%.     

微波消解ICP-AES法测定螺蛳肉中镉

镉是一种对人体有害的微量元素 ,即使存在于香烟中的微量镉经呼吸道进入人体 ,蓄积到一定程度也会危害健康[1] ,国家标准明确规定了食品中镉的限量[2 ] ,对食品中镉的测定方法有石墨炉原子吸收光谱法、火焰原子吸收光谱法、比色法[3] ,香烟中镉的测定已报道的有阳极溶出伏安法和微分电位溶出法[4 ,5] 。这些方法普遍存在样品处理时间长 ,试剂用量大 ,有些还使用对环境有污染的试剂。微波消解作为样品分析的新技术 ,由于消化样品能力强、速度快、消耗化学试剂少 ,金属元素不易挥发损失 ,污染小 ,空白值低等优势 ,已被广泛应用于化学分析前处…     

石墨炉原子吸收光谱法直接测定细胞中镉的研究

以镉孵育的肝癌细胞(HepG2)为研究对象,对基体改进剂种类、细胞个数以及原子吸收条件等相关参数进行了研究,在此基础上建立了石墨炉原子吸收光谱直接测定细胞中镉含量的方法.该方法可用于直接测定几百个(约400个)细胞中的镉;还可以用于人全血样品中镉的直接测定,血液样品体积仅需10μL(血细胞约107个).方法 的检出限为...     

快速升温石墨炉原子吸收光谱法直接测定水中铅镉银

水中铅、镉和银的含量均为国家生活饮用水卫生标准中的重要指标。对于铅、镉和银的测定,国标法分别用吸光光度法、火焰原子吸收光谱法和石墨炉原子吸收光谱法。石墨炉原子吸收光谱法具有较高的灵敏度,但由于其常规程序升温时间较长,影响了分析速度。     

双硫腙-乙酸丁酯萃取火焰原子吸收光谱法测定水中痕量银

火焰原子吸收光谱法简便、快速,广泛用于分析环境样品中金属元素。但对于水中痕量银,却因灵敏度低而不能直接测定。因此人们寻求其它的技术途径[1],如离子交换分离 火焰原子吸收光谱法,虽然它可以满足痕量银的测定要求,但其样品处理复杂,测定时间较长;APDC MIBK萃取火焰法因其生成的络合物不稳定,测定有困难;石墨炉技术则因仪器昂贵、操作要求严格而难以推广普及。本法在文献[2]的基础上探讨了双硫腙 乙酸丁酯萃取火焰原子吸收光谱法测定水中痕量银。本法灵敏度高,操作简便、快速,回收率和精密度较好。1　试验部分1.1　原理样品溶液…     

石墨炉原子吸收法直接测定全血中镉和铅

直接测定人体血镉和血铅较为困难。本文介绍用铂作基体改进剂以提高镉、铅的灰化温度,在灰化阶段除去产生高背景吸收的蛋白,而不发生镉、铅的挥发损失。实现了不需消化样品、络合提取等复杂的化学前处理,用石墨炉原子吸收法和校正曲线直接测定。同时应用衬钽技术,大大延长了石墨管的使用寿命。     

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。     

分离富集-原子吸收光谱法测定锌锰电池中铅和镉

对用原子吸收光谱法测定锌锰电池中铅和镉结果的可靠性进行了研究。对于典型的4R25电池,试液中主要成分锌和锰总量超过40 g.L-1,直接用普通稀释法得不到准确的结果。采用CL-7301萃淋树脂微色谱柱将电池试液中铅和镉与基体快速分离,用火焰原子吸收光谱法测定铅和镉,当铅和镉的含量较高时,可以将样品预稀释后采用在线稀释技术直接测定铅和镉。     

浊点萃取分光光度法测定水中痕量镉

镉是环境中广泛存在的有害元素之一,具有强烈的致畸和致癌毒性,是环境监测中常规分析的项目之一。因此测定环境水样中镉的含量具有重要的应用价值。目前,测定镉的方法主要有电感耦合等离子体质谱法[1]、石墨炉原子吸收光谱法[2]、火焰原子吸收光谱法[3]和分光光度法[4]等。相对于前几种分析方法,分光光度法具有操作简单、价格低廉等特点。     

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.     

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.     

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.     

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.     

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.     

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.     

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.