用阳极溶出内标法测定高纯铝中杂质

本文利用阳极溶出法和内标法的基本原理和方法,在pH3.5左右的三氯化铝支持电解质中,加入定量内标离子,然后利用被测杂质离子与内标离子的波高比与浓度作图,进行定量测定高纯铝中锌、镉、铅、铜杂质元素。试验结果表明,方法准确度和精密度良好。微克/h_(Zn、Pb、Cu)/h_(Cd)(以下简称K)基本为一常数。采用镉作内标元素。     

高纯硫酸镉中杂质的化学光谱分析

本文报导用离子交换-光谱法测定高纯硫酸镉中铜、铅、锌、蛇、锰、镁、钙和铝等八个杂质元素,操作简便,方法的相对标准偏差不大于±30％,灵敏度为3×10~(-5)-5×10~(-6)％。     

电感耦合等离子体质谱法测定铅锌矿区土壤中微量元素

铅锌矿区土壤样品经高压密闭消解罐消解处理,采用电感耦合等离子体质谱法测定其中铬、砷、镉、镍、铜、锰、锌、钴和铅等9种微量元素的含量。通过加入盐酸降低硫对铜测定的干扰,运用干扰方程校正光谱干扰,用内标校正消除基体影响。砷的检出限(3s)为1×10-4mg·g-1,其余8种元素的检出限(3s)均为1×10-5mg·g-1。9种元素的回收率在90.1%~109.1%之间。方法用于土壤标准物质(GBW 07401、GBW 07404、GBW 07406)分析,测试结果与标准值相吻合。     

ICP-OES内标法同时测定纺织品中砷、锑、铅等9种可提取元素

建立了ICP-OES内标法同时测定纺织品中砷、锑、铅、镉、铬、钴、铜、镍、汞等9种有害元素的检测方法.采用钇(Y)作为内标添加物,有效补偿了酸性汗液中钠元素造成的背景干扰.结果表明:砷、锑、铅、镉、铬、钴、铜、镍、汞等9种元素的谱线强度与其浓度在(0.03～0.30)～10 mg/L范围内均具有良好的线性关系,检出限分...     

石墨消解-动态反应池模式-电感耦合等离子体质谱法测定烟用香精和料液中5种元素的含量北大核心CSCD

将烟用香精和料液样品0.3 g(精确至0.001 g)置于全自动石墨消解仪消解罐中,分3次加入消解液(共计10 mL硝酸、1 mL高氯酸),在170℃的最高消解温度下,样品消解完全.所得溶液用水定容至50 mL,采用电感耦合等离子体质谱法(ICP-MS)测定其中砷、铅、镉、铬、镍等元素的含量.以铟为内标,铬、镉、镍、铅、砷元素的测量同位素分别为^(52)Cr、^(111)Cd、^(60)Ni、^(208)Pb、^(75)As,使用动态反应池(DRC)模式消除了铬、砷元素的质谱干扰,铬、镉、镍、铅等元素的测定选择氦气碰撞模式,砷元素的测定选择氢气反应模式.结果表明,5种元素的质量浓度在一定范围内与各元素与内标计数值的比值呈线性关系,检出限(3s)为0.016~0.035 mg·kg^(-1).按标准加入法进行回收试验,各元素回收率为91.5%~111%,相对标准偏差(n=6)为0.28%~3.1%.方法用于10个烟用香精和料液样品的分析,铬、砷、镍的检出量分别为0.019~0.061 mg·kg^(-1),0.039~0.061 mg·kg^(-1)和0.022~0.031 mg·kg^(-1),镉和铅未检出.     

应用内标的PAN-Ni体系快速共沉淀分离富集和火焰原子吸收光谱测定食盐中铅

应用1-(2-吡啶偶氮)-2-萘酚(简写作PAN)-镍(Ⅱ)共沉淀体系,以锰(Ⅱ)为内标,在pH 9的氨性缓冲溶液中对食盐中痕量铅(Ⅱ)进行快速共沉淀富集,并用火焰原子吸收光谱法测定铅的含量,对共沉淀条件作了优选。在优化的条件下,试液中作为内标的锰(Ⅱ)及铅(Ⅲ)离子均定量地与PAN-Ni(Ⅱ)共沉淀析出。锰(Ⅱ)、铅(Ⅱ)及镍(Ⅱ)均匀地存在于沉淀中,而且在铅(Ⅱ)、锰(Ⅱ)之间或镍(Ⅱ)、锰(Ⅱ)之间存在着一定的比例关系。因此,根据共沉淀中铅(Pb1)及锰(Mn1)的吸光度APb1,AMn1的比值即可求得铅的含量(w%),原试样中铅含量(Pb0)可由下式计算:mPb0=APb1/AMn1.mMn0。试验结果表明,经过共沉淀分离,基体干扰已予消除。此方法的检出限为3.18×10-2mg.L-1。应用于3种不同来源的食盐的分析,算得铅含量测定值的RSD(n=6)均小于4.3%,回收率测得值在95.4%至101.6%之间。     

电感耦合等离子体质谱法测定铅锌矿尾矿渣中铜、铅、锌和镉

采用硝酸-氢氟酸-高氯酸溶解样品,用电感耦合等离子体质谱法测定了铅锌矿尾矿渣中的铜、铅、锌和镉。以铑为内标元素,选择63 Cu,66Zn,208 Pb,114 Cd作为测量同位素。铜、铅、锌的线性范围为200μg·L-1,镉的线性范围为1.0μg·L-1,检出限(3s)分别为0.04,0.10,0.03,0.003μg·g-1。测定值的相对标准偏差(n=11)在0.39%~2.2%之间。用此方法分析标准物质,测定值与认定值相符。     

Ni(Ⅱ)-PAR共沉淀-原子吸收光谱法测定水样及奶茶粉中的锌

研究了用4-(2-吡啶偶氮)-间苯二酚(PAR)为沉淀剂,以Ni(Ⅱ)为载体离子的共沉淀体系快速共沉淀分离富集水样和奶茶粉中的锌,并用火焰原子吸收光谱(FAAS)测定。共沉淀过程受体系酸度、载体镍、沉淀剂PAR的用量及陈化时间的影响。结果显示,在pH 5.0的条件下,能够定量共沉淀试样中的锌。方法检出限为3.77μg/L,用于水样及奶茶粉的加标回收率为97.0%～99.1%,相对标准偏差为1.3%～4.1%。     

用悬汞电极阳极溶出法测定高纯铝中杂质

应用悬汞电极阳极溶出法测定高纯材料中数量级为10~(-4)—10~(-7)％微量杂质(或更低含量),在1956年以后才被应用于分析化学中。本文利用悬汞电极阳极溶出法直接测定高纯铝中微量锌、镉、铅、铜,灵敏度分别为:锌:3×10~(-5)％,镉:2×10~(-6)％,铅:2×10~(-6)％,铜:3×10~(-5)％。 (一)仪器     

电感耦合等离子体质谱法测定高纯铝中杂质元素

高纯铝样品经盐酸(1+1)溶液微波消解,采用电感耦合等离子体质谱法测定所得样品溶液中钛、铁、铜、锌、镓、银、镉、铟和铅等杂质元素的含量。选择适当的待测元素的同位素克服了质谱干扰,定量加入50μg·L~(-1)铯和锗内标元素有效地校正了基体效应。选用碰撞室技术消除了多原子离子对部分被测元素的干扰。结果表明:方法的检出限(3s)在0.003～0.042μg·L~(-1)之间。高纯铝样品中9种元素测定结果的相对标准偏差(n=10)在2.9%～9.5%之间。方法用于精铝标准样品(R11C)的测定,结果与认定值基本相符。     

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.     

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.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

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.