固相萃取-电感耦合等离子体原子发射光谱（ICP-AES）法测定地下水中三种重金属

为拓宽固相萃取技术在生态环境监测领域应用范围,建立了树脂固相萃取前处理ICP-AES法测定地下水中铅、铬、镉含量的方法。经前处理条件优化,硝酸洗脱液浓度5%、缓冲溶液pH 7、洗脱速率10 mL/min及进样体积为500mL条件下,铅、铬、镉等三种重金属回收率均可以达到95%以上。该方法中各目标元素在0.02~20 μg/L范围内线性关系良好,相关系数均大于0.999;铅、铬、镉方法测定下限分别0.56μg/L,0.04μg/L,0.24μg/L满足评价要求;方法精密度RSD值在0.44%~5.49%;加标回收率范围分别在98.55%~101.84%、98.5%~104%、95.5%~105%。经监测井实样测试,铅、铬、镉结果处于《地下水质量标准》（GB/T14848-2017）I类限值范围内。该方法干扰小,易操作,为相关国家标准修订提供参考。     

催化极谱法测定痕量铬的研究

本文研究了含氨介质中铬(Ⅲ、Ⅵ)-α,α’-联吡啶-亚硝酸钠体系的电化学行为。建立了测定痕最铬的方法。测定铬的范围为0.004～0.028μg/mL和0.04～0.23μg/mL,检测下限为2.0×10~(-3)μg/mL,用以测定生物样品中良量铬,变异系数为0.8%。     

胶束增敏催化动力学光度法测定土壤中的总铬量

在HAc-NaAc缓冲溶液介质中,在乳化剂OP存在下,痕量铬(Ⅵ)对过氧化氢氧化中性红的褪色反应有很强的催化作用,据此建立了测定微量铬(Ⅵ)的催化动力学光度法。该方法测定铬(Ⅵ)含量的线性范围为0.0~40.0μg/(25 mL),检出限为2.7×10-4μg/mL。该方法用于土壤中总铬量的测定,加标回收率为95.0%~101.0%,相对标准偏差为0.11%~0.17%。     

环境水样中六价铬的化学发光测定新方法

罗丹明B和过氧化氢在碱性介质中反应产生化学发光。本文研究了铬(Ⅵ)对该化学发光反应的发光强度的影响。实验表明,化学发光强度与铬(Ⅵ)的浓度在0.04—8μg/mL的范围内有线性关系。同时该法用于电镀废水中铬(Ⅵ)的测定。该法简单、适用、方法相对标准偏差3％,测定铬(Ⅵ)的检出限0.028μg/mL。     

电感耦合等离子体发射光谱法测定不锈钢中的铬、镍、锰、铜、钛、铝

建立电感耦合等离子体发射光谱仪同时测定不锈钢中铬、镍、锰、铜、钛、铝6种元素含量的方法。用20mL王水溶解样品,铬、镍、锰、铜、钛、铝的分析谱线分别为283.563,231.604,259.373,324.754,334.941,308.215 nm。铬、镍、锰、铜、钛、铝的质量浓度与其信号强度均呈良好的线性关系,线性相关系数均不小于0.999,检出限分别为0.007,0.009,0.002,0.007,0.002,0.008μg/mL。测定结果的相对标准偏差为0.17%～2.80%(n=6),加标回收率为96.50%～103.70%。用该法测定国家标准物质,测定值与标准值一致,相对误差为0.05%～3.03%。该方法准确、可靠,可用于不锈钢中铬、镍、锰、铜、钛、铝的测定。     

电感耦合等离子体原子发射光谱法测定牙科修复体产品中的铍、镉

建立电感耦合等离子体原子发射光谱法测定牙科镍铬合金、钴铬合金烤瓷修复体产品金属部分中铍、镉含量的分析方法。以6 mL浓硝酸、2 mL浓盐酸和0.5 mL氢氟酸为消解液,采用微波消解法消解样品。铍、镉的质量浓度在5～50 mg/L范围内与光谱强度呈良好的线性关系,线性相关系数均为1.000,铍,镉的检出限分别为0.8,1.8μg/L。加标回收率为96.2%～104.6%,测定结果的相对标准偏差为2.1%～4.4%(n=10)。该方法具有良好的精密度与准确度,可用于牙科镍铬合金、钴铬合金烤瓷修复体产品金属部分中铍、镉的测定。     

浊点萃取-石墨炉-原子吸收光谱法测定镍铬合金牙冠在人工唾液中浸出的铬(Ⅵ)

将镍铬合金牙冠样品置于人工唾液10mL中,于37℃浸泡4周。分取此唾液2.00mL,加入2g·L~(-1)二苯碳酰二肼(DPC)溶液0.1mL,Triton X-114(5+95)溶液0.6mL及硫酸(1+1)溶液0.5mL,加水定容为10 mL后,于40℃加热20min,使铬(Ⅵ)与DPC络合并溶入Triton X-114相中,实现铬(Ⅵ)的浊点萃取分离。将黏稠的Triton X-114液相分出,加入硝酸与甲醇(1+99)混合液定容至1mL。按所述仪器工作条件用石墨炉-原子吸收光谱法测定其中的铬(Ⅵ)量,进样量为10μL。铬(Ⅵ)的质量浓度在5.0μg·L~(-1)以内与相应的吸光度呈线性关系,检出限(3s/k)为0.088μg·L~(-1)。分别加1.0μg·L~(-1)铬(Ⅵ)标准溶液于6件牙冠样品溶液中,按方法测定后求得平均回收率为96%。对同一样品重复测定6次,计算其相对标准偏差为3.8%。     

双波长双指示剂催化动力学光度法测定微量铬(Ⅵ)

基于在pH=4.5的HAc-NaAc缓冲介质中,微量铬(Ⅵ)催化过氧化氢氧化混合指示剂(中性红和亚甲基蓝)褪色的指示反应,建立了双波长双指示剂催化动力学光度法测定微量铬(Ⅵ)的新方法。方法的线性范围为0.005～0.3μg/mL,检出限为8.7×10-4μg/mL。该方法操作简单,灵敏度高,选择性好,用于环境水样中微量铬(Ⅵ)的测定,回收率在98.5%～102.5%之间,结果满意。     

流动注射-化学发光法测定血浆中盐酸阿霉素

在碱性介质中,K3[Fe(CN)6]与鲁米诺产生化学发光反应,盐酸阿霉素对该体系的发光强度具有显著的抑制作用,且光信号的减小值(△I)与盐酸阿霉素的浓度在一定的范围内成正比。基于此建立了一种流动注射化学发光法测定盐酸阿霉素的新方法。在最优实验条件下,该方法的线性范围为0.4～2.5μg/mL,检出限为2.9×10-2μg/mL。对1.2μg/mL的盐酸阿霉素连续平行测定11次,其相对标准偏差为2.1%。该方法用于血浆中盐酸阿霉素的分析,回收率在98.4%～102.0%之间。     

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     

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%.     

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.     

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.     

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

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.     

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.     

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.