纳米二氧化钛分离/富集-石墨原子吸收光谱法测定环境样品中痕量镉

以石墨炉原子吸收(GFAAS)为检测手段,研究了纳米二氧化钛(TiO2,锐钛型)对金属Cd(Ⅱ)的吸附性能,考察了吸附和解吸的主要影响因素.结果表明,在较宽的pH范围内,纳米TiO2对Cd(Ⅱ)具有良好的吸附性能,3.0 mol/L HCl能将所吸附的Cd(Ⅱ)完全洗脱.在优化的实验条件下,具有吸附容量大、吸附速度快的特点.本法的检出限(3σ)为10.6 ng/L;相对标准偏差(RSD)为1.5%,(n=7,C=2.0 μg/L),富集50倍.本法测定标准样品的测定值与参考值吻合.用于土壤类样品中Cd(Ⅱ)的测定,结果令人满意.     

纳米二氧化钛分离富集石墨炉原子吸收光谱法测定水样中痕量铅

提出了纳米TiO2分离富集,GFAAS测定水样中痕量铅的新方法。详细考察了纳米TiO2对铅的吸附行为,结果表明：在pH4．0时,Pb^2 可被纳米TiO2定量富集,吸附于纳米TiO2上的Pb^2 可用0．1mol／L的硝酸完全解脱。本法对Pb^2 的检出限为52ng／L,相对标准偏差为4．7％(n=10,C=0．02mg／L)。本法已用于实际水样中铅的测定,结果满意。     

硼氢化钾还原-原子荧光光谱法研究纳米TiO2对Hg(Ⅱ)的吸附行为

以硼氢化钾还原-原子荧光光谱法(KBH4-AFS)为检测手段，研究了纳米TiO2(锐钛型)对Hg(Ⅱ)的吸附行为，考察了影响吸附和解脱的主要因素，并考察了共存离子的干扰影响。在较宽的pH范围内，纳米TiO2对汞具有良好的吸附性能。在优化的实验条件下，具有吸附容量较大和吸附速度较快的特点，该法测定汞的检出限为0．004ng/mL，相对标准偏差(RSD)为3．3％(n=9，ρ=0．05ng/mL)。将本法应用于标准样品GSS-8、GSS-4的测定，其测定值与标准值吻合。已应用于实际水样中汞的测定。     

用等离子体原子发射光谱法研究纳米二氧化钛对钨酸根离子的吸附行为

利用纳米二氧化钛（TiO2)比表面积大，吸附能力强的特点，采用ICP-AES检测手段系统地研究了纳米TiO2对钨酸根离子（WO4^2-）的吸附行为，详细考察了影响吸附和解脱的主要因素，以及共存离子的干扰影响。在优化的实验条件下，本法测定W（Ⅵ）的检出限为0.044μg/g，相对标准偏差RSD=2.3%(n=9,C=5.0mg/L)。本法已应用于水系沉积物（GBW07302）中W的测定，测定值与标准值基本吻合。     

碲化镉纳米晶荧光猝灭法测定痕量铜(Ⅱ)

制备了水溶性的CdTe纳米晶。基于铜（Ⅱ）离子在pH=7,80的磷酸盐缓冲溶液中对该纳米晶的荧光具有较强的猝灭作用,建立了一种测定铜（Ⅱ）离子的新方法。在最佳条件下,体系的相对荧光强度（△F）与铜（Ⅱ）离子的浓度呈线性关系,线性范围为8．0～320．0μg／L,其线性回归方程为：△F=-8．18-0．14c（μg／L）;检出限为3．24μg／L。本方法用于实际样品中痕量铜的测定,结果令人满意。     

纳米氧化铝微柱富集-等离子体发射光谱法测定植物中痕量稀土元素

以负载了1-苯基-3-甲基-4-苯甲酰基-吡唑酮[5](PMBP)的纳米氧化铝为微柱吸附材料，采用等离子体原子发射光谱法(ICP-AES)，系统地研究了其在动态条件下对稀土离子Sc^3 、Y^3 和La^3 的吸附性能，并确定了最佳吸附及解脱条件。实验结果表明：在pH为4．5时，分析物均可被上述吸附材料定量吸附；用0．5moL／L盐酸溶液可将吸附在微柱上的稀土离子完全解脱。本法对Sc^3 、Y^3 和La^3 的检出限分别为0．16、0.19和0．39μg／L；相对标准偏差(RSD)分别为2．7％、3．2％和1．6％(n=9，C=0．5mg／L)。方法应用于植物标样中痕量Sc、Y和La的测定，其测定值与标样值吻合很好。     

纳米TiO2微柱分离富集测定环境样品中的微量硒

以处理过的纳米TiO2为微柱吸附材料,采用流动注射技术进行微量硒的分离富集,考察了纳米TiO2微柱对Se(IV)的吸附性能,探讨了溶液的pH值、试样流速、试样体积、洗脱液浓度和用量以及干扰离子等因素的影响。实验结果表明,pH在1～6范围内,试样流速为0.5 mL/min,纳米TiO2对Se(IV)具有良好的吸附性能,吸附率可达97%,动态饱和吸附容量为7.92 mg/g;选用1 mL 0.1 mol/L NaOH溶液可将吸附的Se(IV)完全洗脱,富集倍数为40。本法的检出限(3σ)为0.13 mg/L,相对标准偏差为1.56 %。将本法应用于国家标准样品GBW07280的分析,测定值与参考值一致。     

Oscillography Double Potentiometric Titration of Cadmium（ll） Using Modified Platinum Electrode

制备了镉修饰铂电极,用循环伏安法表征了Cd（II）在该电极上的吸附特性,探讨了电极的响应机理．通过优化试验条件,建立了一种新的测定Cd（II）的示波双电位滴定法．在1．0mol／L的六次甲基四胺溶液中（pH=6．0）,用制备的修饰铂电极作为双指示电极,以EDTA标准溶液滴定Cd（II）,利用示波器屏幕上荧光点的显著最大位移指示滴定终点．Cd（II）在9．0×10。～3．5×10。mol／L时,回收率为99．8％～100．3％．该修饰电极具有良好的稳定性和重现性,在含有1．0×10。mol／LCd（II）的溶液中,连续13次测定,所得终点电位值均在37mV左右,其相对标准偏差（RSD）0．02％．应用该方法测定含镉样品,RSD值m=71小于0．81％．回收率为99．71％～100．09％．测定结果与指示剂法测定佰相符．     

纳米TiO_2微柱分离富集-分光光度法测定环境样品中的微量硒

以处理过的纳米TiO2为微柱吸附材料,采用流动注射技术进行微量硒的分离富集,考察了纳米TiO2微柱对Se(Ⅳ)的吸附性能,探讨了溶液的pH值、试样流速、试样体积、洗脱液浓度和用量以及干扰离子等因素的影响。实验结果表明,pH在1～6范围内,试样流速为0.5mL/min,纳米TiO2对Se(Ⅳ)具有良好的吸附性能,吸附率可达98.3%,动态饱和吸附容量为7.92mg/g;选用1mL0.1mol/LNaOH溶液可将吸附的Se(Ⅳ)完全洗脱,富集倍数为40。本法的检出限(3σ)为0.13mg/L,相对标准偏差为1.56%。将本法应用于国家标准样品GBW07280的分析,测定值与参考值一致。     

镉-向红菲啰啉体系吸附伏安法测定镉

在pH＝4.1的0．03mol／L邻苯二甲酸氢钾介质中，Cd（Ⅱ）-向红菲啉络合物于悬汞电极上在-0．65V（vs．SCE）电位处产生一灵敏的吸附还原峰，利用1．5次微分技术进行测定，络合物波峰峰值epp与Cd（Ⅱ）浓度在1．0×10－9～1．0×10－7mol／L范围内呈良好的线性关系，检出下限为7×10－10mol／LCd（Ⅱ），本文详细研究了测定镉的最佳条件，对络合物在汞电极上的电化学行为进行了初步探讨。方法用于环境水样中微量镉的测定，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%.     

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.     

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.     

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.     

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.     

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.