TODGA树脂小柱分离-多接收电感耦合等离子体质谱（MC-ICP-MS）法测定岩石样品中Nd同位素比值

通过改进岩石样品分析物Nd的化学分离,实现Nd同位素比值的准确分析,为研究青藏高原岩石成因,揭示物质来源提供技术支持。采用TODGA萃淋树脂分离基体及其与Nd相邻的稀土元素,多接收电感耦合等离子体质谱（MC-ICP-MS）法测定Nd同位素比值,建立了简捷实用的地质样品Nd同位素分析方法。样品HF-HNO3分解, HNO3(3 mol/L )- H3BO3(0.12 mol/L)提取,上柱后,先用6 mL HCl(2.8 mol/L)淋洗干扰轻稀土,再用6 mL HCl(2.2 mol/L)淋洗分析物Nd,Nd淋洗液由MC-ICP-MS测定其同位素比值。分析国际岩石标准物质BCR-2、BHVO-2和AGV-2,所得143Nd/144Nd同位素比值（平均值 ± 2σ）分别为0.512638 ± 0.0000007、0.512990 ± 0.0000012和0.512792 ± 0.000016,这些同位素数据在误差范围内,与推荐值和文献值完全一致。方法适合各种类型地质样品,为西藏不同地区不同岩石提供了可靠的Nd同位素分析数据。     

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。     

天然样品中锂的分离及其同位素比值的测定

以锂元素标准样品和K、Na、Ca、Mg元素标准样品的混合溶液为主要研究对象,采用阳离子交换树脂AG-50W X8(0.032~0.098 mm粒径)来分离富集L i,探索不同淋洗介质(包括盐酸、硝酸以及与甲醇、乙醇的混合)对L i分离纯化的最佳效果。在对比研究的基础上,建立了一种有效分离提纯天然样品中L i的方法。用本方法分离了水体、土壤、岩石等天然样品中的L i,并用MC-ICP-MS准确测定了L i同位素组成。研究结果表明,该方法的精度在0.1‰~1.0‰,与目前文献报道的分析方法具有相似的精度。经过流程前后单元素标准L i同位素比值(7δL i)的比较,发现化学处理过程所产生的同位素分馏约为0.3‰,化学处理的流程空白可以忽略不计。该方法测定海水7δL i值为(31.6±1.0)‰,与前人的分析结果吻合。因此,本方法可用于测定天然样品中的L i同位素组成。     

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.     

地质样品中钛的化学分离及双稀释剂法钛同位素测定

建立了玄武岩和橄榄岩样品中钛(Ti)的化学分离方法,特别是对于含低Ti而高Fe和Mg的橄榄岩样品中Ti的化学分离方法进行了探索。实现了通过双稀释剂技术校正的多接收器等离子体质谱(MC-ICP-MS)法测定玄武岩和橄榄岩的Ti同位素组成。玄武岩样品Ti的化学分离采用DGA和AG1-X8两柱法;橄榄岩样品Ti的化学分离采用DGA和AG1-X8三柱法。Ti同位素比值使用MC-ICP-MS测定,测定过程中的仪器质量分馏使用双稀释剂法校正。采用SRM 979 Cr同位素标准物质的~(53)Cr/~(52)Cr=0.11339对Ti同位素标准溶液SRM 3162a和~(47)Ti-~(49)Ti双稀释剂进行标定。而后,测定分别加入了~(47)Ti-~(49)Ti双稀释剂的Alfa Ti相对于SRM 3162a Ti的δ~(i/46)Ti,并用于监控测试过程。使用双稀释剂法测定Alfa Ti的结果为:δ~(49/46)Ti=-1.77‰±0.08‰(2sd),δ~(48/46)Ti=-1.20‰±0.05‰(2sd),δ~(47/46)Ti=-0.61‰±0.03‰(2sd),本方法的外部精度≤0.03‰/amu,优于样品-标样交叉法。     

气相色谱同位素比质谱测定不同产地鱼油中5种不饱和脂肪酸碳同位素比值

以IAEA-600咖啡因(δ13C-27.771‰)作为溯源标准,建立了气相色谱同位素质谱技术测定鱼油中功能因子亚油酸(LIA)、亚麻酸(LNA)、花生四烯酸(ARA)、二十碳五烯酸(EPA)、二十二碳六烯酸(DHA)等5种不饱和脂肪酸碳稳定同位素比值δ13C的分析方法。鱼样品先经HCl水解,乙醚液液萃取脂肪,提取的脂肪在2 mol/L KOH-甲醇溶液中反应生成脂肪酸甲酯,采用强极性毛细管气相色谱柱(Sil-88 100 m×0.25 mm×0.2μm)分离,稳定同位素比质谱测定。方法经日内、日间和人员比对验证,表明测定结果稳定,标准偏差小于0.82%。收集了不同产地的241个淡水鱼和深海鱼,对于提取的天然鱼油进行5种不饱和脂肪酸同位素比值分析,测得天然鱼油中5种不饱和脂肪酸同位素比值(δ13C)在-32.87‰~27.07‰之间,经计算,鱼油中不饱和脂肪酸δ13C值与硬脂酸δ13C值之比在-5.79~1.88之间,同时测得了相同的产地、品种鱼油中不饱和脂肪酸δ13C的分布范围,构建了天然鱼油的同位素指纹特征数据库,用于鉴定鱼油真伪。将不同浓度玉米油添加至天然金枪鱼油中进行测定,证明δ13C值的变化与掺入C4植物油量呈良好的线性关系,方法可根据δ13C值的变化鉴别掺假的鱼油。     

HAc溶解碳酸盐岩测定87Sr/86Sr值实验方法研究

传统的碳酸盐岩的sr同位素比值测定因为采用HCl溶样,往往导致非碳酸盐组分的溶解,引起测定值偏高,采用HAc溶样可以防止样品中非碳酸盐组分的溶解,同时也避免过多的杂质离子进入溶解液,从而使^87Sr／^86Sr测定值趋于准确和可靠;通过2.5mol/L HAc溶解碳酸盐矿样和4.0mol/L HCl溶解残渣样的最后质谱测定的^87Sr／^86Sr值比较,证实碳酸盐岩中非碳酸盐组分的^87Sr／^86Sr值较碳酸盐组分高。     

红酒中的~(87)Sr/~(86)Sr同位素比测定

研究了多接收电感耦合等离子体质谱(MC-ICP-MS)测定红酒样品中87Sr/86Sr同位素比的分析方法,并用建立的分离测定方法参加了欧洲参考物质与测量研究所(IRMM)组织的CCQM-P105国际比对,即红酒中87Sr/86Sr同位素比的分析比对.红酒样品经微波消解后,采用Dowex 50W×8树脂分离纯化锶,用MC-ICP-MS精确测定锶组分中的87Sr/86Sr同位素比,同时对测量结果的不确定度进行了分析和评定.     

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.     

生物体中氨基酸单体碳稳定同位素测试方法研究

氨基酸作为蛋白质的基本组成单位,是重要的生命物质,其单体碳同位素研究在生物地球化学、生态学、生物体代谢和环境科学等领域具有重要意义。该文优化了海参和海藻氨基酸提取和纯化流程,通过N-新戊酰基-O-异丙酯(NPP)方法衍生化后,分别用气相色谱-质谱(GC-MS)和气相色谱-燃烧-同位素比值质谱(GC-C-IRMS)测试其浓度和碳同位素组成。结果显示,15种氨基酸单体的分离效果较好,回收率为46.4%～96.3%,各氨基酸在1.0～16.0μmol/L范围内线性关系良好(r²为0.987～0.999)。15种氨基酸单体衍生物δ¹³C值的标准偏差均小于0.30‰(n=10),在0.6～2.0 mmol/L浓度范围内δ¹³C的平均误差为±0.24‰,方法检出限为0.6 nmol。海参和海藻样品各氨基酸单体δ¹³C值的范围分别为-31.10‰～-8.58‰和-30.53‰～-13.76‰,标准偏差均在0.33‰以内,可满足生物体氨基酸单体碳同位素的测试精度需求。     

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.