电感耦合等离子体原子发射光谱(ICP-AES)法测定锂云母中的锂、钽、铌等7种元素

采用HNO_3-HF-HClO_4的酸体系将实验样品置于聚四氟乙烯坩埚中进行消解,用稀硝酸定容。用电感耦合等离子体原子发射光谱(ICP-AES)法测定锂云母中的锂、钽、铌等7种常见元素。通过对国家标准物质GBW07154、GBW07152的验证,测定值均在标准值的误差范围内,检出限为0.001 8～0.11μg/g,样品测定的相对标准偏差(RSD,n=6)在0.95%～3.5%,加标回收率在95.0%～108%。方法快速、准确,试剂用量少,适合大批量锂云母矿样品中Li、Ta、Nb等元素的分析测定。     

电感耦合等离子体原子发射光谱(ICP-AES)法测定尼日利亚铌钽锂矿石中的铌、钽、锂

经过三种样品前处理实验对比,选择采取氢氟酸-高氯酸-王水溶样,酒石酸-王水浸取,电感耦合等离子体原子发射光谱(ICP-AES)法测定尼日利亚地区铌钽矿石中铌、钽、锂元素。对元素的分析谱线、酒石酸浓度等工作条件进行了优化,选择各元素的最佳分析谱线,并进行加标回收实验,探讨了各元素的加标回收率。选取Nb 269.7nm、Ta 240.0nm、Li 670.78nm作为仪器分析谱线,计算得到的方法检出限分别为:Nb 0.5μg/g、Ta 1.5μg/g、Li 15.0μg/g。对比各种溶样方法,选取一种最简洁方便的样品前处理途径,经国家一级标准物质GBW07153、GBW07155和GBW07185验证,测定值的相对误差为-2.82%～1.77%,方法精密度(RSD,n=6)为0.11%～1.2%,测定尼日利亚地区铌钽锂矿石中的铌、钽、锂元素,结果无显著性差异,方法能够满足尼日利亚铌钽矿石中相关组分的准确测定。     

电感耦合等离子体原子发射光谱(ICP-AES)法测定尼日利亚铌钽锂矿石中的铌、钽、锂

经过三种样品前处理实验对比,选择采取氢氟酸-高氯酸-王水溶样,酒石酸-王水浸取,电感耦合等离子体原子发射光谱(ICP-AES)法测定尼日利亚地区铌钽矿石中铌、钽、锂元素。对元素的分析谱线、酒石酸浓度等工作条件进行了优化,选择各元素的最佳分析谱线,并进行加标回收实验,探讨了各元素的加标回收率。选取Nb 269.7 nm、Ta 240.0 nm、Li 670.78 nm作为仪器分析谱线,计算得到的方法检出限分别为:Nb 0.5μg/g、Ta 1.5μg/g、Li 15.0μg/g。对比各种溶样方法,选取一种最简洁方便的样品前处理途径,经国家一级标准物质GBW07153、GBW07155和GBW07185验证,测定值的相对误差为-2.82%~1.77%,方法精密度(RSD,n=6)为0.11%~1.2%,测定尼日利亚地区铌钽锂矿石中的铌、钽、锂元素,结果无显著性差异,方法能够满足尼日利亚铌钽矿石中相关组分的准确测定。     

多种酸溶矿ICP-AES测定稀有金属矿中锂铍铌钽锡

为了准确快速地测定不同样品中的锂、铍、铌、钽、锡含量,采用HCl-HNO_3-HClO_4-HF混合酸消解试样,采用经研究效果较好的介质酒石酸-稀盐酸-H_2O_2定容,用ICP-AES测定稀有金属矿中的锂、铍、铌、钽、锡等元素。所加试剂引起的干扰通过空白实验予以消除。锂、铍、铌、钽、锡谱线原子发射强度与P(Li)的在0~20μg·mL~(-1)、P(Be)的在0~10μg·mL~(-1)、P(Nb)和P(Ta)的在0~5μg·mL~(-1)、P(Sn)的在0~1μg·mL~(-1)范围内呈良好的线性关系,相关系数R分别为1.0000、0.99999、0.9998、0.9997和0.9977。检出限分别为1.0μg·g~(-1)、0.5μg·g~(-1)、2.5μg·g~(-1)、5μg·g~(-1)、0.012μg·g~(-1),方法用于稀有金属矿中锂、铍、铌、钽、锡的分析,相对标准偏差(RSD,n=11)在1.22%~6.01%,加标回收率在95.6%~106%;用于标准样品分析,测定值与认定值相符。方法快速、准确,适合大批量稀有金属矿样品的分析测试。     

电感耦合等离子体光谱法测定锂辉石选矿产品中铌和钽

用碘化铵灼烧,氢氟酸-硫酸分解矿样,不经分离,电感耦合等离子体光谱法测定锂辉石选矿产品中铌和钽(以其五氧化物表示)。Nb2O5的检出限为8.4×10-9g,Ta2O5的检出限为1.1×10-8g。相对标准偏差:铌为0.8%,钽为1.2%,测定范围为5×10-4%~20.00%。     

ICP-MS法测定聚酯纤维中TiO2含量

采用湿法和微波法对聚酯纤维样品进行消解,利用电感耦合等离子体质谱联用仪(ICP-MS)对样品中TiO2含量进行了测定,得到湿法消解样品测定值2 857.46μg/g(相对标准偏差为1.08%),微波消解样品测定值2599.21μg/g(相对标准偏差为2.76%).分别测定了两种消解方法的检出限,湿法消解检出限为4.0 ...     

稀土铌钽矿中铌、钽、锆量的电感耦合等离子-原子发射光谱法测定

本文研究了用电感耦合等离子-原子发射光谱(ICP-AES)法测定稀土铌钽矿中的铌、钽、锆。实验考察了不同溶样方法及其对样品的溶解程度,确定了称样量及其熔融物提取的方法,选择了分析线波长,确定了仪器工作条件,考察了共存元素的干扰情况。对方法的准确度及精密度进行了考察。本法测定Nb、Ta和Zr的线性范围分别为0.50~5.00μg/mL、0.10~1.00μg/mL和5.00~50.00μg/mL,对于0.050%~0.20%Nb2O5、0.010%~0.20%Ta2O5、0.50%~5.00%ZrO2测定的相对标准偏差均小于7%。     

电感耦合等离子体质谱(ICP-MS)法测定地质样品中镉、铬、钨、钽和铌

地质样品成分复杂,各元素物理化学性质差异大,在有盐酸介质存在的的情况下,敞口湿法一次消解容易出现易挥发元素Cd、Cr等测定结果不稳定;敞口湿法一次消解,难溶元素W、Ta、Nb等消解不完全。本文以HNO3—HF—HClO4—H2SO4为消解体系,用电热板湿法重复消解样品,建立起了ICP-MS同时测定地质样品种不同性质Cd、Cr、W、Ta、Nb的样品分析方法。通过优化仪器参数条件,选择带碰撞池He气模式（ked）,以50g/L酒石酸为测定介质,采用三通在线加入103Rh和185Re内标补偿基体效应和信号飘逸,解决了难溶元素W、Ta、Nb结果偏低、易挥发元素Cd、Cr结果精密度较差的问题。该方法用国家一级标准物岩石、土壤、水系沉积物质验证,相对标准偏差(RSD)小于8%,准确度(△lgC)均≤0.05,其测定值与标准值一致,用实际样品进行加标回收试验,回收率在89%～110%之间,方法检出限均小于多目标区域地球化学调查规范（DZ/T 0258—2014）。该方法分析流程较简单,结果准确可靠,可满足测定大批量地质样品中Cd、Cr、W、Ta、Nb元素含量的要求。     

电热消解-电感耦合等离子体质谱(ICP-MS)法测定土壤中镱铪钽钨四种高能稀土元素

镱(172 Yb)、铪(178 Hf)、钽(181 Ta)、钨(182 W)四种稀土元素质量数均高于170,第一电离能分别为601、656、759、767kJ/mol,高于平均电离能486kJ/mol,属于难电离元素,且在土壤中含量较低。通过选择合适的消解体系,采用碰撞模式去除多原子离子干扰,选择193Ir内标校正基体干扰,建立了电热消解-电感耦合等离子体质谱法测定土壤中镱铪钽钨四种高能稀土元素的方法。4种元素校准曲线的线性均大于0.999,检出限在0.05～0.5μg/g,用土壤标准物质GSS-8、GSS-13进行验证,平均相对标准偏差(RSD)在3.2%～12.4%,加标回收率为88%～115%,各元素的测定值与标准值吻合。     

纸上层析分离-ICP-AES测定稀有金属矿中的铌钽

采用HF、HNO_3溶解样品,纸上层析分离富集铌、钽,焦硫酸钾分解铌钽氧化物,酒石酸浸取,ICP-AES测定稀有金属矿中铌钽。研究了溶样用酸、色层分离展开剂比例及展开温度、焦硫酸钾用量、酒石酸浓度等对测定结果的影响,结果表明,采用纸上层析法可使铌钽与其他干扰元素彻底分离,焦硫酸钾熔融后,用酒石酸浸取使铌、钽完全进入溶液,以电感耦合等离子体光谱仪(ICP-AES)进行测定。在20 g/L的酒石酸介质中,ICP-AES测定铌钽的线性范围为0~50μg/mL,检出限为铌0.14μg/mL,钽0.16μg/mL;相对误差小于8%,精密度(RSD)小于6%,可测定矿石中0.001%~40%的Nb_2O_5,Ta_2O_5。该方法可同时测定稀有金属矿中铌钽原矿、精矿及尾矿中铌钽的含量,适合基体复杂、含量差别大的批量样品的检测。     

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%.     

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.     

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.