微波消解-双通道原子荧光光谱法同时测定家禽内脏中的硒和汞

最佳分析条件下,采用微波消解样品,以HCl为预还原剂和测定介质,用氢化物发生-原子荧光法同时测定了家禽内脏中硒汞的含量。硒、汞的质量浓度分别在12.00～24.00μg/L范围与相应的荧光强度呈线性关系,方法的检出限分别为0.065μg/L和0.010μg/L,相对标准偏差(RSD)分别在1.3%～2.8%和2.4%～4.3%(n=5)之间,回收率范围分别为93.6%～101.1%和92.2%～98.6%。     

共沉淀富集氢化物发生-原子荧光光谱法同时测定山药中砷和硒

建立了共沉淀富集氢化物发生-原子荧光光谱法同时测定山药中痕量砷、硒。考察了共沉淀剂种类、用量,pH值及硼氢化钾浓度的影响。在优化实验条件下,在0～40μg/L范围内,砷、硒的线性相关系数分别为0.994、0.9967,检出限分别为0.0007μg/L、0.0011μg/L,相对标准偏差砷为1.06%、硒为0.77%。该法用于山药中砷、硒的测定,其平均加入回收率分别为95.4%和90.6%。该方法样液用量少,操作简便,适用于食品中痕量砷、硒的测定。     

微波消解试样-原子荧光光谱法测定土壤中硒碲

应用HG-AFS法及微波加热试样消解法测定了土壤中硒和碲的含量,对试样消解参数、仪器工作条件及氢化物发生反应条件等作了试验并讨论.该方法测定硒及碲的检出限均为0.01μg·g-1,荧光强度与硒及碲的质量浓度在5～100μg·L-1及0.5～10μg·L-1范围内呈线性关系.应用此方法分析了3个土壤试样,测定值的相对标准偏差(n=6)均小于5%.用标准加入法作了回收试验,硒的回收率在92.0%～102.6%之间,碲的回收率在90.1%～98.8%之间.     

AE-HG-AFS测定长期汞暴露人群补硒后尿中硒的形态

建立了一种利用阴离子交换高效液相色谱与氢化物发生原子荧光光谱联用同时测定四、六价硒及硒代半胱氨酸(SeCys)形态的方法。优化了六价硒的还原条件及仪器检测参数,以不同浓度的柠檬酸铵作为流动相,在10 min内同时分离了四、六价硒及硒代半胱氨酸(SeCys)。采用加标法定量,加标回收率在90%～119%之间,相对标准偏差为1.6%～3.1%(100μg/L),四、六价硒及硒代半胱氨酸(SeCys)的检出限分别为0.32μg/L、0.47μg/L和0.44μg/L(进样量为100μL)。应用该法对长期汞暴露人群补硒后尿中的小分子硒的形态进行了分析,仅检测到硒代半胱氨酸(SeCys)。     

氢化物发生-原子荧光光谱法(HG-AFS)测定特硬铅合金中硒和碲

建立了氢化物发生-原子荧光光谱法(HG-AFS)测定特硬铅合金中硒和碲的分析方法。试样经硝酸和酒石酸溶解,硫酸沉淀分离基体铅元素。移取部分试液,在40%盐酸介质中直接用氢化物发生-原子荧光光谱法(HG-AFS)测定样品中的硒;另移取部分试液,加入氢溴酸挥发除去砷、锑、锡、硒等元素,在40%盐酸介质中用氢化物发生-原子荧光光谱法(HG-AFS)测定样品中的碲。考察了测定的最佳条件、铅及共存元素对测定的影响。测定硒和碲的相对标准偏差分别为7.5%～9.3%和3.6%～13.0%,加标回收率分别为88%～92%和98%～102%。准确度和精密度均能满足分析需要,具有较强的实用性。     

顺序注射HG-AFS法测定富硒农产品中无机硒和有机硒

本文建立了顺序注射氢化物发生原子荧光法测定硒的分析方法.探讨了富硒农产品中无机硒和有机硒的分离及提取方法.优化了仪器的工作条件,考察了KBH4浓度和酸介质浓度对硒原子荧光强度的影响.方法的线性范围为1～100μg/L,检出限为0.02μg/L,无机硒的回收率为95.0%～104.0%.     

断续流动氢化物发生原子荧光法测定富硒食品中的微量硒

建立了断贯流动氢化物发生原子荧光法测定富硒食品中微量硒的方法。样品用硝酸高氯酸混酸消化，在优化的实验条件下，标准曲线的线性范围为0-100μg/L，相关系数为0.9999。检测限0.06545μg/L。应用于测定鸡蛋，富硒米和富硒盐中微量硒的测定。回收率分别为90.6%,98.5%和104.3%。     

电感耦合等离子体质谱（ICP-MS）法与氢化物发生-原子吸收光谱（HG-AAS）法测定土壤中硒含量的对比研究

基于氢化物发生器与原子吸收光谱联用(HG-AAS),测定土壤样品中硒的含量,并与电感耦合等离子体质谱(ICP-MS)法测定值进行了对比。在两种仪器的最佳工作条件下,测定土壤硒的含量,实验结果表明:ICP-MS法和HG-AAS法对土壤硒含量测定的线性范围分别为0.85~100.00μg/L和0.08~16.00μg/L,检出限分别为0.25μg/L和0.02μg/L,精密度分别为1.3%和2.1%;用加标回收实验和测定国家标准土壤样品(GSS-7)对这两种方法的准确性进行了验证,ICP-MS法和HG-AAS法的加标回收率分别为96.7%~99.4%和94.9%~99.5%,GSS-7标准土样的结果均在标准值范围内,说明这两种测定土壤中硒含量的方法是准确可靠的。HG-AAS法测定线性范围窄,部分样品需要稀释,而且氢化物发生系统是手动进样,导致操作复杂,分析周期长;ICP-MS法仪器测定快速,但是仪器昂贵。     

氢化物原子荧光光谱法测定水中微量砷和硒

研究了氢化物发生-原子荧光光度法测定水中微量砷和硒的方法。结果表明,检出限:砷为0.0518μg/L,硒为0.0524μg/L;11次测定的相对标准偏差为0.36％～0.62％;标准回收率:砷为96.8％～100.9％;硒为95.9％～103.7％。方法简便、快速、灵敏,适于生活饮用水、地表水和水源水中微量砷、硒的同时测定。     

离子交换色谱-氢化物发生双道原子荧光法同时测定砷和硒形态

建立了离子交换色谱-氢化物发生双道原子荧光联用同时测定4种As形态和3种Se形态的方法,并优化了各种实验参数。采用PRP-X100阴离子交换分析柱可以在10min内同时分离、检测As和Se形态。在8%HCl和1.5%(m/V)KBH4的氢化物反应条件下,进样量100μL,各形态的检出限为:As(Ⅲ)0.2μg/L、DMA0.3μg/L、MMA0.2μg/L、As(Ⅴ)0.3μg/L、SeCys0.6μg/L、Se(Ⅳ)0.5μg/L、SeMet3μg/L。当各As形态浓度为100μg/L、各Se形态浓度为200μg/L,各形态的精密度RSD(n=7)均小于5%。当各As形态浓度范围为5～100μg/L、SeCys和Se(Ⅳ)浓度范围为10～200μg/L、SeMet浓度范围为50～200μg/L时,各形态均可得到良好的线性关系,线性相关系数均大于0.9992。用建立的方法测定了富硒营养品中的As和Se形态,加标回收率在91%～115%之间。     

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.     

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.     

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.     

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 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.