地热水锂组分快捷分离纯化及同位素测定

锂是一种战略性矿产资源, 青藏高原蕴藏着富锂地热水, 锂同位素可以用来示踪其物质来源和演化过程。本文采用AG50W-X8阳离子交换树脂对地热水锂组分进行了快捷分离纯化, 建立了利用多接收电感耦合等离子质谱仪(MC-ICP-MS)测定锂同位素的方法。移取适量的地热水样品加热蒸干, 转化成0.20 mol/L HCl溶液后上柱, 继续使用0.20 mol/L HCl纯化锂组分。当洗脱液中Na/Li比值≤1.2且锂的回收率超过99%时, 可以在MC-ICP-MS上直接测定锂同位素比值。应用该方法测定了标准物质L-SVEC、IRMM-016和标准海水IAPSO的δ7Li值, 结果分别为0.01±0.34‰、-0.02±0.46‰和30.75±0.35‰, 与推荐值相符合。利用L-SVEC配制的标准溶液检查了MC-ICP-MS的长期稳定性, 外精度要好于0.4‰ (2σ)。在测定青藏高原地热水样品时, 本方法获得了准确的δ7Li值, 可为青藏高原富锂地热水的成因机制研究提供技术支撑。     

多接收器电感耦合等离子质谱精确测定钕同位素组成

报道了本实验室近两年来Neptune MC-ICP-MS测试Nd同位素的结果。测试结果显示样品化学分离中伴随的大量铈对钕同位素组成测定没有影响;而分离后残余少量钐,在一定范围内(钐/钕<0.04)可以直接扣除,获得准确的Nd同位素组成。Neptune MC-ICP-MS和热电离质谱(TIMS)平行测定实际地质样品表明,Neptune MC-ICP-MS可以精确测定Nd同位素组成,与经典的TIMS技术相比,MC-ICP-MS可以获得与TIMS相媲美的数据精度,而且分析时间缩短,效率明显提高。     

ICP–OES法测定八氧化三铀中杂质元素钨

以ICP–OES法测定八氧化三铀中杂质元素钨。采用浓HNO3–浓HCl、浓HNO–HF、3 mol/L HNO3三步酸溶方案,利用CL–TBP萃淋树脂将铀基体分离,淋洗液基质为3 mol/L HNO3,淋洗液流速为1 mL/min。弃去最初2 mL死体积淋洗液后接收10 mL,分离回收率平均值为95.93%,线性方程为y=539.71x+16.6,相关系数r2=0.999 7,4水平样品测定结果的相对标准偏差为0.39%~3.12%(n=6)。用该方法对标准物质进行测定,测定结果在参考值范围内。     

酸及其浓度对多接收器等离子体质谱法测定Cu和Zn同位素的影响

运用多接收器等离子体质谱法 (MC-ICP-MS)测定同位素时,必须进行仪器质量歧视校正,而酸浓度对仪器质量歧视的影响是过去被忽视的问题.本实验以Cu和Zn同位素分析为例,研究了在HNO3和HCl介质进样条件下酸浓度对仪器质量歧视的影响.结果表明:HNO3 的浓度对Cu和Zn同位素的仪器质量歧视有显著影响,但二者并不同步;HCl的浓度在0.05 mol/L ～ 0.3 mol/L范围内对Cu和Zn同位素的仪器质量歧视没有影响.这说明与HNO3相比,HCl是一种更好的进样介质.在0.1 mol/L HCl 介质条件下,65Cu/63Cu 和66Zn/64Zn比值测定的长期重现性 (外部误差)均为0.00008 (2sd),比在HNO3介质下的重现性有明显改善.     

多接收等离子质谱高精度测定现代人齿中Mg同位素

Mg是构成牙齿重要组分,其含量和同位素组成可记录居民生活地域、饮食习惯以及口腔健康信息等重要信息.本研究建立了高精度多接收等离子质谱(MC-ICP-MS)测定牙齿中Mg同位素方法.牙齿样品经微波消解仪消解,后采用AG50W-X8阳离子树脂分离溶液中的Mg元素,以1 mol/L HNO3为介质上柱,40 mL1 mol/L HNO3洗脱Na+等杂质离子,再以30 mL 1 mol/L HNO3收集Mg元素,60 mL 1 mol/L HNO3洗去其它杂质,蒸干Mg收集液.MC-ICP-MS进行Mg同位素组成测定.MC-ICP-MS仪器自身的质量分馏利用“样品-标准”交叉技术(“Sample-standard”bracketing technique)解决.实验结果表明,利用AG50W-X8阳离子树脂,可在保证Mg回收率的情况下,将牙齿样品中的Mg和其它基质元素彻底分离,且不造成同位素分馏.采用此方法对现代人离体牙牙釉质中Mg同位素进行分离测定,牙齿的δ25Mg在较大的范围变化(-1.38‰ ～4.59‰).本方法为利用人牙齿中Mg同位素研究Mg的暴露水平、环境污染等信息提供重要的实验和理论依据.     

大气气溶胶中锂的化学分离与同位素比的质谱检测

通过大量条件实验,确定离子交换法分离Li+、Na+的最佳淋洗条件柱填料为Dowex-50w×8阳离子树脂,柱高为12 cm,淋洗液为0.8 mol/mL HCl-50%CH3OH,淋洗速度约为0.48 mL/min.采用离子交换法分离大气气溶胶中Li与其它元素,采用Li3PO3为样品涂样形式的热电离质谱法测量了大气气溶胶中Li的同位素比值.化学分离过程中Li的回收率大于95%,大气气溶胶中稳定Li同位素6Li/7Li比值为0.08206.     

镁同位素分析技术应用于葡萄酒辨别的探索研究

建立了阳离子树脂富集镁的方法.以1 mol/L HNO3为淋洗液、AG W50-X8阳离子树脂富集镁.方法回收率为(101.6±1.2)％.以H2 (2.1 mL/min)、He(7.0 mL/min)混合碰撞气消除12C12 C+,12C21H+等干扰的MC-ICP-MS分析方法.分析了40种葡萄酒中镁同位素组成,结果表明:不同产地葡萄酒中镁同位素组成差异明显;而且,来自同一产区不同葡萄园的葡萄酒中镁同位素组成也有显著差异.这表明镁同位素具有区分不同产地葡萄酒的能力,而且地理分辨率较高.对于部分镁同位素组成差异不明显的样品,结合元素分析手段,可以准确区分.     

三正辛胺(TOA)分离贵金属的系统研究 Ⅰ.反相萃取色层法分离七个贵金属

本文系统详细地研究了七种贵金属彼此分离以及与贱金属分离的可能条件。此种工作尚未见报道。用三正辛胺作固定相。分别用1mol/L HCl、6mol/LHCl、2mol/L HNO_3—2mol/L HCl、3mol/L HNO_3-2mol/L HCl、4mol/L HNO_3-2mo1/L HCl和5％硫脲-1mol/L HCl为淋洗液,可以将Rh、Ru、Pd、Pt、Ir、Os、Au分步淋洗下来,达到彼此完全分离。为了使Rh(Ⅱ)与贱金属分离,必须将RhC1_6~(3-)转化为RhBrb_6~(3-),然后在另一色层柱上使它与贱金属分离。合成矿样的分析结果符合分析要求。     

多接收电感耦合等离子体质谱(MC-ICP-MS)法测定土壤的铁同位素组成

随着分析技术的发展，铁（Fe）同位素（δ56/54Fe）在土壤科学中得到了广泛的应用，可以用来研究铁在土壤圈中的迁移、转化等过程。为了确保不同类型样品中的铁同位素测量的准确性，需要标定一系列标准物质的铁同位素组成。但是目前对于土壤标准物质铁同位素数据的报道几乎没有，这阻碍了不同实验室间铁同位素数据质量进行对比。为了对不同实验室间的铁同位素数据进行比较，需要对土壤标样的铁同位素进行标定。在本研究中，我们使用硝酸-氢氟酸-高氯酸混酸对土壤样品中的硅酸盐和有机质进行消解，利用阴离子交换树脂（AG1-X8，0.038-0.074 mm）对土壤样品中的铁与基质元素进行了分离。为了获得可靠的纯化流程，我们检验了不同浓度的盐酸对基质的淋洗效果。结果表明，当盐酸浓度从4.0 mol/L变化到7.0 mol/L时，基质元素都能有效地被分离干净。最后我们采用5.0 mol/L的盐酸将基质元素从阴离子树脂中淋洗出来，然后利用0.3 mol/L的盐酸将铁元素收集起来。铁同位素组成利用多接收电感耦合等离子体质谱仪进行测定。通过对实验室标准铁溶液（ISS-Fe和USTC-Fe）的长期的监测，本分析方法δ56/54Fe的外精度好于±0.05‰（2SD）。我们分析了两个玄武岩标样（BCR-2和BHVO-2）的铁同位素组成，其δ56/54Fe值分别为0.08±0.05‰和0.09±0.05‰，均与文献值在误差范围内是一致的。此外，我们测量了六个土壤标样（SRM2709，SRM2709a，SRM2710a，SRM2711，SRM2711a和GBW07453）的铁同位素组成，其δ56/54Fe值分别为0.05±0.01‰，0.07±0.02‰，-0.11±0.02‰，0.15±0.03‰，0.14±0.03‰和0.10±0.01‰。该研究为土壤铁同位素研究提供了有用的数据库。     

锶特效树脂萃取色谱耦合热电离同位素质谱法测定海水中锶同位素研究

采用锶特效树脂,以萃取色谱法将锶离子自基体中分离,详细介绍了锶特效树脂萃取原理,进行了实验条件优化。采用HNO3消解海水样品,以HNO3(8.0mol/L)为介质上柱,用HNO3(8.0mol/L)淋洗,样品中的锶离子被强烈吸附在树脂柱上,再以HNO3(0.05mol/L)洗脱,Sr被解吸。收集淋洗液,蒸干,采用热电离同位素质谱仪测定海水样品中的87Sr/86Sr比值。结果表明,利用锶特效树脂,可将锶与基体元素(K,Na,Mg,Ba)分离,并能有效分离同位素测定中干扰元素Ca和Rb。消除了基体干扰,提高了分离效率,达到灵敏测定。     

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.     

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.     

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.     

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.     

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%).