离子色谱法检测酸性镀铜液中的微量氯离子

采用Na2CO3-NaHCO3为淋洗液和抑制电导检测,对酸性镀铜液中的微量氯离子进行检测。采用AgNO3作为沉淀剂使Cl-分离富集,再用Na2S2O3溶液溶解沉淀后进行检测,可以很好地消除酸性电镀液中高浓度SO4^2-的干扰。该方法线性良好,Cl^-的检出限为0.01μg/mL,回收率在98.6%-101.7%之间,由于该方法能够很好地消除大量SO4^2-的干扰,在电镀铜工业中对酸性镀铜液中氯离子的监控可发挥作用。     

火焰原子吸收法间接测定二氧化硅中的氯

在酸性环境中,氯离子与银离子生成沉淀,经氨水溶解后,以火焰原子吸收法测定银,从而间接测定氯离子的含量。本方法测定氯的线性范围为1.0~30μg/mL,检出限为0.059μg/mL,回收率为95%~105%。将此法应用于二氧化硅中氯离子的测定,结果满意。     

过氧化氢氧化酸性铬兰K催化动力学光度法测定溴离子

在中性条件下,游离的Br-对H2O2氧化酸性铬兰K褪色反应具有催化作用。基于此建立了测定微量Br-的催化光度分析方法。结果表明,该方法最大吸收波长为525 nm,测定的线性范围为0.4μg/mL～11.2μg/mL,检出限为0.321μg/mL。方法用于河水中微量Br-的测定,结果令人满意     

离子色谱法同时测定蛋白胨中氯离子、硫酸根离子、碘离子

建立离子色谱法测定蛋白胨中氯离子、硫酸根离子、碘离子3种阴离子的含量。采用氢氧化钾淋洗液发生器产生的KOH溶液为流动相,进行梯度淋洗,流量为1.0 mL/min。氯离子、硫酸根离子的质量浓度分别在0.5～200μg/mL范围内与色谱峰面积呈良好的线性关系,碘离子的质量浓度在0.75～50μg/mL范围内与色谱峰面积呈良好的线性,线性相关系数均不小于0.999,检出限分别为0.003,0.01,0.22μg/mL。样品加标回收率为92.94%～96.59%,测定结果的相对标准偏差为2.42%～5.70%(n=9)。该方法灵敏、高效,可用于蛋白胨中氯离子、硫酸根离子、碘离子的快速准确测定。     

悬浮进样阻抑火焰原子吸收光谱法测定甘薯粉条中的微量铝

本文利用铝对钙吸收的阻抑效应,建立了悬浮进样-火焰原子吸收光谱法快速测定甘薯粉条中微量铝的方法。结果表明,当底液中的钙为20.0μg/mL时,测定铝的线性范围是0.5~8.0μg/mL,检出限为0.25μg/mL。本法用于三种不同粉条中铝的测定,相对标准偏差为0.7%~1.9%,加标回收率为95%~104%。     

酸性铬兰K催化光度法测定水中的氟含量

研究了稀硫酸介质中,游离的F-对溴酸钾氧化酸性铬兰K褪色反应具有催化作用,基于此建立了测定微量F-的催化光度分析的方法。结果表明,有色溶液的最大吸收波长为523 nm,测定的线性范围为0.2～6.0μg/mL,检出限为0.1031μg/mL。方法用于水中微量F-的测定,相对标准偏差为0.65%～0.76%,回收率99.5%～105%。     

催化光度法测定水中的氟

在中性溶液中,游离的F-对H2O2氧化酸性铬兰K褪色反应具有催化作用,基于此建立了测定微量F-的催化光度分析的新方法.结果表明,有色溶液的最大吸收波长为522 nm,测定的线性范围为0.4～11.2 μg/mL,检出限为9.9×10-4 μg/mL.该法用于水中微量F-的测定,结果令人满意.     

罗丹明6G催化动力学荧光光度法测定水中氟化物

在弱酸性条件下,NaF对KBrO3氧化罗丹明6G的反应具有催化作用,使罗丹明6G的荧光减弱。基于此建立了测定微量氟化物的催化动力学荧光光度分析新方法。结果表明:罗丹明6G溶液的荧光激发波长和发射波长分别为535nm、556nm,测定的线性范围是0.04~2.8μg/mL,检出限为0.038μg/mL。该法可用于水中微量氟化物的测定。     

Cu(Ⅰ)-烯丙基硫脲的络合吸附波

在pH3.3的邻苯二甲酸氢钾底液中,Cu(Ⅰ)-烯丙基硫脲体系有一灵敏的还原波,其单扫导数峰电位E_p=-0.32V(vs.SCE),可用于微量铜的测定。工作曲线线性范围为0.002—0.12μg/mL,检测极限为0.001μg/mL。文中探讨了该波的还原机理,认为是络合吸附波。     

微波消解-端视ICP-AES测定茶叶中微量重金属元素

采用微波消解-端视等离子体原子发射光谱(ICP-AES)测定茶叶中微量重金属元素Pb、As、Cd、Cu、Fe,并对ICP-AES工作参数及条件进行了优化和选择。Pb、As、Cd、Cu、Fe的检出限分别为2.9×10-3μg/mL、5.2×10-3μg/mL、0.056×10-3μg/mL、0.55×10-3μg/mL、0.59×10-3μg/mL,线性范围为0~10000μg/L,相对标准偏差为1.7%~8.5%;回收率为90%~104%。该方法与国标法比较,结果无显著性差异。本法能用于茶叶测定。     

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%.     

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.