激光剥蚀-电感耦合等离子体质谱:双外标结合基体归一定量校准策略

定量校准策略是激光剥蚀电感耦合等离子体质谱(AICP-MS)分析技术的重要组成部分,直接影响分析数据的质量.本研究评估了现有玻璃标准物质定值不确定度的相对大小,并探究了NIST、MPI-DING和USGS系列玻璃标准物质之间的基体效应.结果表明,NIST610的定值不确定度优于其它玻璃标准物质,在本实验条件下,NIST、MPI-DING和USGS系列玻璃标准物质之间的基体效应可忽略不计.在此基础上提出了双外标结合基体归一定量校准策略,外标分别为NIST610和StHs6/80-G.此策略克服了由于NIST610主量成分与地质样品差别大而造成的主量元素准确度差以及StHs6/80-G中某些微量元素含量低、定值不确定度较大等缺点.对比采用3种定量校准策略(单外标NSIT610基体归一法、单外标StHs6/80G基体归一法和双外标基体归一法)校准的ML3B-G数据可知,双外标基体归一法有效避免了单外标基体归一法的不足,并提高了分析数据的准确度.采用双外标结合基体归一定量校准策略校准了BCR-2G、CGSG-2和KL-2G中的主量元素和微量元素.结果表明,绝大多数分析数据在定值不确定度范围内,验证了此校准策略的实用性.同时,本研究得到的主量微量元素数据进一步补充了BCR-2G、CGSG-2和KL-2G的定值数据库.     

激光剥蚀电感耦合等离子体质谱法中生物样品的元素分馏效应研究

采用213 nm-纳秒激光剥蚀系统对生物基体样品的剥蚀颗粒进行研究,优化了激光剥蚀条件.在剥蚀能量为25%,束斑直径为200 μm,剥蚀速率为20 μm/s,频率为20 Hz,载气为700 mL He + 700 mL Ar时,信号强度及稳定性最佳.以31P为内标元素,最佳剥蚀条件下,考察了56个元素的相对分馏因子.结果表明,生物基体的剥蚀颗粒相较于NIST 610 玻璃标样更大,达到3 μm;生物基体中元素分馏效应相较于玻璃基体小,大多数元素的相对分馏因子达到1.0 ±0.1.探讨了生物基体中元素分馏机理,分析了生物基体相较于玻璃基体剥蚀颗粒大,而相对分馏因子未明显增大的原因.一方面可能是粒径3 μm的颗粒进入电感耦合等离子体后能原子化;另一方面,大的剥蚀颗粒的富集效应相对较小.进一步对分馏效应的影响因素进行研究,发现分馏效应与激光剥蚀能量、激光频率和扫描速率相关,并且与元素的氧化物沸点负相关,与氧化物键能和电离能正相关.     

193nmArF准分子激光剥蚀-等离子体质谱测定富钴结壳中的稀土元素

采用193nm ArF准分子(Excimer)激光剥蚀ICP—MS测定了富钴结壳中痕量稀土元素。比较了^27Al、^49Ti作为内标元素时稀土元素的LA—ICP—MS分析信号的响应行为。结果表明,^27Al与稀土元素具有相似的激光剥蚀行为以及等离子体激发、电离特征;以Al为内标元素,NIST610玻璃标准为外标,可有效抑制基体效应和灵敏度漂移的影响。方法的检出限为1．2～15．8ng／g,用于标准参考物质中稀土元素的测定,测定结果的相对标准偏差(n=5)在2．2％～6．4%,测定值与标准参考值的相对误差小于6．5％。     

激光剥蚀-电感耦合等离子体质谱法测定纯钌中19种杂质元素

建立了激光剥蚀-电感耦合等离子-体质谱法(LA-ICP-MS)法测定纯钌中Mg、Al、Fe、Ni、Cu、Zn、Rb、Rh、Pd、Mo、Ag、Cd、Sn、Ba、Ir、Pt、Au、Pb和Si等19种杂质元素的分析方法。优化了仪器参数：给出了激光能量为60%,剥蚀孔径为110 μm,扫描速率为50 μm/s,脉冲频率为10Hz,载气流量为0.74L/min条件下,信号强度和稳定性最佳。由于钌标准样品难以获得,本文选择用纯钌粉样品,高温高压溶解后,采用ICP-MS定值所测元素（除硅外）。根据钌粉样品的ICP-MS定值结果确定了测定元素的相对灵敏度因子（RSF）,对归一法结果进行较正,提高了方法准确度。方法的检出限为：0.001~12.81μg/g,相对标准偏差(RSD)为：10%～30%。采用本方法测定纯钌中杂质元素,结果与ICP-MS测定的结果吻合。     

LA-ICP-MS法测定纯铜及铜丝中的各元素

采用冷等离子体模式,以63Cu为内标,研究了单点激光剥蚀电感耦合等离子体质谱法(LA-ICP-MS)测定纯铜及铜丝中各元素的方法。优化了仪器参数;给出了样品直径对结果的影响,锌的信号随着直径的减小而减弱,硒的信号随着直径的减小而增强;研究了分馏效应,Cd,Sb,Pb,Bi分馏因子(FI)在0.80左右有分馏效应;采用不同系列铜标准物质制作了校准曲线以考察基体效应,Mn,Ni,Zn,Pb,Bi的线性相关系数大于0.99,基体效应不明显,其它元素有基体效应。建立了测定纯铜及铜丝中P,Mn,Fe,Ni,Zn,As,Se,Ag,Cd,Sn,Sb,Pb,Bi等元素的直接测定方法,但硫不能测定,也不能用56Fe作为铁的检测同位素,标准物质的测定值与认定值基本吻合,除Mn含量低外,其它元素的RSD(n=5)在2.1%~16%之间。     

低温等离子体剥蚀-电感耦合等离子体质谱联用对电路板镀层的深度分析

建立了基于低温等离子体(Low temperature plasma)剥蚀系统将固体样品直接引入电感耦合等离子体质谱(ICP-MS)并用于电路板镀层中Au,Ni和Cu的深度分析.此实验中采用介质阻挡放电(DBD)方式产生低温等离子体探针,逐层剥蚀样品表面,由ICPMS检测元素信号.对DBD所用放电气体种类、外加电场功率、放电气体流速和采样深度等实验条件进行优化.在优化条件下,应用LTP-ICPMS在30 s内完成电路板镀层(20 μm Au/10 μm Ni/Cu基底)的逐层剥蚀和深度分析,元素种类和分层顺序与X射线光电子能谱(XpS)相吻合,镀层的分辨率可拓展至微米水平,表明此技术可直接用于固体样品的深度分析.     

激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)法测定涂层氧化锆颗粒铌层中24种微量杂质元素

本文针对涂层氧化锆颗粒涂层分析需求,建立了LA-ICP-MS分析Nb涂层和Zr基质中24种微量杂质元素测试方法,获得了最佳剥蚀条件(激光束斑44微米、能量密度6J/cm2、剥蚀频率5 Hz);并利用NIST610标样作为外标、Nb和Zr作内标分别校正了Nb涂层及Zr基质层;方法检出限: 1.5μg/g (Fe)、1.16 (Cr)、0.36(Ni),其它21中元素检出限0.01 ~695.72μg/g。该方法成功测定了60件Nb涂层和Zr基质样品中24种微量杂质元素;获得了26种元素深度剥蚀信号vs时间轮廓图,激光剥蚀涂层时间为16～110s;建立了涂层厚度测试方法,利用LA-ICP-MS技术结合环境扫描电镜能谱技术测定了球体涂层的厚度, 获得了准确的LA深度剥蚀率0.3714μm/s,并成功测定了60件样品中涂层的厚度(5.942~40.854 μm),实现了涂层氧化锆涂层成分定量。     

激光剥蚀电感耦合等离子体质谱分析硅酸盐矿物基体效应的研究

标样与样品之间基体效应的差异是影响LA-ICP-MS分析结果准确度的重要因素,而元素的相对灵敏度因子(RSF)是基体效应的重要表征.本研究考察了17个玻璃标样中49种常见元素及10个电子探针天然硅酸盐矿物标样中10种主、微量元素RSF的差异,比较了以Ca,Al,Si为内标对基体效应的补偿作用及元素分馏效应的影响.结果表...     

激光剥蚀-电感耦合等离子体质谱法测定土壤中15种微量元素

在土壤标准样品中加入内标元素铼,将其压片后直接进样,将激光聚焦在样品表面下100μm,在以下条件下进行激光剥蚀(LA):(1)剥蚀载气氦气流量为600mL·min-1;(2)剥蚀光斑直径为110μm;(3)剥蚀速率为50μm·s-1。剥蚀后形成的气溶胶进入电感耦合等离子体质谱仪(ICP-MS),对其中15种微量元素(铍、钒、铬、钴、镍、铜、锌、镓、砷、镉、锡、锑、铊、铅、铋)进行测定。采用标准加入法,通过校准曲线外推得到各目标元素的含量。检出限(3s)为0.01～0.08μg·g~(-1);用此方法分析了2个土壤标准样品(GSS-3和GSS-14),除铍、锑和镉,其他元素所得测定值均在认定值的允许不确定度范围内,且相对误差(RE)均不超过10%;对土壤标准样品(GSS-14)重复测定5次,15种元素测定值的相对标准偏差(n=5)均在10%以内。     

激光剥蚀-电感耦合等离子体质谱(ICP-MS)法测定纯钌中19种杂质元素

建立了激光剥蚀-电感耦合等离子体质谱(LA-ICP-MS)法测定纯钌中Mg、Al、Fe、Ni、Cu、Zn、Rb、Rh、Pd、Mo、Ag、Cd、Sn、Ba、Ir、Pt、Au、Pb和Si等19种杂质元素的分析方法。优化了仪器参数,给出了激光能量为60%,剥蚀孔径为110μm,扫描速率为50μm/s,脉冲频率为10 Hz,载气流量为0.74 L/min条件下,信号强度和稳定性最佳。由于钌标准样品难以获得,因此选择用纯钌粉样品,高温高压溶解后,采用ICP-MS法定值所测元素(除硅外)。根据钌粉样品的ICP-MS法定值结果确定了测定元素的相对灵敏度因子(RSF),采用相对灵敏度因子(RSF)对所测结果进行校正,方法准确、快速,检出限为0.007~12.8μg/g,相对标准偏差(RSD)为10%~30%。测定纯钌中杂质元素,结果与ICP-MS法测定的结果吻合。     

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.     

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.