固体基质室温燐光猝灭法测定人发和水中痕量汞

基于水杨基荧光酮羧甲基纤维素铅发光分子微球(Pb(CMC)2-THBF)在滤纸基质上可发射强而稳定的室温燐光,由此建立了Pb(CMC)2-THBF固体基质室温燐猝灭测定痕量汞的新方法.Hg2 的含量在2.5~100.0(pg/mL)内与ΔIp值成线性关系,其线性回归方程为ΔIp=12.73 0.4699CHg2 (pg/mL),r=0.9991,检出限为3.2×10-13g/mL.该方法用于人发和水样中痕量汞的测定,结果满意.同时探讨了固体基质室温燐光猝灭测定痕量汞的机理.     

固体基质室温燐光分析法测定痕量银

基于AgCl·PVA·Ag+ 吸附FIn- 所形成的离子缔合物AgCl·PVA·Ag+ ·FIn- 能在滤纸基质上发射强而稳定的室温光信号的特性 ,建立了以滤纸为基质的固体基质室温光测定痕量银的新方法。该离子缔合物对应于聚乙烯醇 (PVA)存在下Fajans(法扬斯 )法的终点。在一定条件下 ,离子缔合物的光强度与吸附层的Ag+ 含量成正比 ,线性范围为 1.72～ 8.6× 10 - 1 2 g 斑 ,(0 .4 μL 斑 ) ,工作曲线对应的回归方程ΔIp =2 80 .81+35 4 5mAg+ (10 - 1 2 g 斑 ) ,n =6 ,相关系数r =0 .9995。该方法快速、灵敏、准确。用于人发、茶叶中银的测定 ,与AAS法基本相符。     

浊点萃取-胶束增稳室温燐光法测定水样中痕量α-萘乙酸

提出了用非离子表面活性剂Triton X-100作萃取剂的浊点萃取-胶束增稳室温燐光法测定痕量α-萘乙酸的新方法.就溶液pH、试剂浓度、平衡温度和时间等实验条件对浊点萃取的影响及后续使用的胶束增稳室温燐光法的测定条件进行了探讨.在最佳条件下,线性范围为3.0×10-8～2.0×10-6 mol/L;检出限1.3×10-8 mol/L;方法用于强化水样中痕量α-萘乙酸的测定,回收率95%～104%;相对标准偏差2.0%～3.5%.     

钴(Ⅱ)-甲基百里香酚蓝络合剂-亚硝酸根络合吸附波的研究及应用

在pH 8.5、0.04 mol/L NH3*H2O-NH4Cl缓冲溶液中,钴-甲基百里香酚蓝络合剂(MTB)在NaNO2存在下,于-1.23 V(vs.SCE)产生一尖锐、灵敏的二次导数极谱波,峰电流与钴(Ⅱ)浓度在5.0×10-8～2.0×10-6 mol/L范围内呈线性关系;检出限为1.0×10-8 mol/L.研究了该波的性质及电极反应机理,证明该波为络合吸附波.峰电流由中心离子钴(Ⅱ)还原产生.络合物在汞电极上的饱和吸附量为5.18×10-9 mol/cm2,符合Frumkin等温式.测得吸附系数β=6.86×105,自由能ΔGθ=33.30 kJ/mol;电子转移数n=2.不可逆吸附的转移系数α=0.58,反应速率常数ks=2.26/s.方法用于VB12和模拟样中痕量钴的测定,结果满意.     

阻抑-褪色光度法测定痕量硅

基于NH3 NH4 Cl缓冲溶液介质中 ,Si 对H2 O2 氧化十六烷基三甲基溴化铵 姜黄素离子缔合物的褪色反应的抑制作用 ,提出了测定痕量硅新的高灵敏的褪色光度法。该方法的表观摩尔吸光系数ε50 0=5 .70× 10 5L·mol-1·cm-1;线性范围为 0 .4～ 3.6 μg/L ;线性回归方程ΔA =2 .2 3× 10 -4 + 0 .0 2 0 17CSi (μg/L) ;相关系数r =0 .9999;测定下限为 2 0× 10 -8g/L。本法用于人发样和水样中痕量硅的测定 ,结果满意。     

煤矸石中痕量钴的催化光度法测定

研究了在 pH 10.0的 Na2B4O7－ NaOH介质中,痕量 Co(Ⅱ )催化 H2O2氧化桑色素的褪色反应,褪色程度与 Co(Ⅱ )量在一定范围内呈线性相关。基于此,建立了一种测定痕量 Co(Ⅱ )的光度法。结果表明方法的检出限为 7.6× 10－ 2 μ g/L, Co(Ⅱ )质量浓度在 0.0～ 50.0 μ g/L范围内符合比尔定律。结合 N530萃取剂萃取分离,测定了煤矸石中的痕量钴。     

纸基质室温燐光法测定痕量6-苄氨基嘌呤的研究

本文经实验发现6-苄氨基嘌呤吸附在滤纸基质上能够发射出室温燐光。较详细地研究了其室温燐光特性。实验表明,在弱碱性条件下,以KI-NaAc作混合重原子微扰剂时,6-苄氨基嘌呤能产生较强的燐光发射,在此条件下,6-苄氨基嘌呤浓度与室温燐光发射强度之间在1×10~(-5)～9×10~(-4)mol/L范围内呈良好的线性关系。检出限为8ng/斑点。     

氢氧化钴修饰玻碳电极的制备及其电化学行为

采用循环伏安法成功制备了氢氧化钴薄膜修饰玻碳电极。考察了影响膜电沉积的因素 ,确定成膜液最佳pH为7.5 ,最佳扫描电位范围为1.00～ -0.20V。讨论了成膜过程及机理 ,成膜关键是Co2 +在电极表面的氧化。制得的膜修饰电极具有表面吸附反应特征 ,表面覆盖量相当于5～6个单层的氧化还原活性物质。膜修饰电极具有良好的稳定性 ,并对H2O2 表现出较高的电催化活性。线性回归方程为 :ΔIpa(μA)=15.92+4.99×104c(H2O2)(mol·L -1)(r=0.9976 ,n=18) ,线性范围为1.72×10 -5～9.92×10 -3mol·L -1,检出限为4.25×10 -6mol·L -1(S/N=3)。     

用2-QADN2,7-金属络合物示波极谱法同时测定铜镍钴镉

本文研究了2-QADN2,7-金属络合物的极谱特性。在pH9.60的缓冲溶液中,Cu(Ⅱ)、Ni(Ⅱ)、Co(Ⅱ)和Cd(Ⅱ)与2-QADN2,7的络合物在-0.37、-0.69、-0.77和-0.82V产生灵敏的极谱波,利用这些波可测定痕量的铜、镍、钴和镉。铜的检测下限为2.0×10~(-8)mol/L,镍、钴及镉的检测下限为5.0×10~(-8)mol/L。提出的方法用于同时测定头发和茶叶中的痕量铜、镍和钴,结果满意。     

同步扫描-化学除氧胶束增稳室温燐光法同时测定痕量菲和荧蒽的研究

本文利用同步扫描-化学除氧胶束增稳室温燐光法研究了痕量菲和荧蒽的同时测定。考察了菲和荧蒽二元混合物中两组分的相互干扰限量。讨论了在胶束体系中菲和荧蒽相互干扰的机理。实验表明,适宜的△λ为186nm。菲和荧蒽的同步峰分别位于480nm和547nm。该法的线性范围为:菲为2.7×10~7～4×10~(-6)mol/L,荧蒽为2.2×10~(7-)～1×10~(-5)mol/L。检出限为:菲为2.7×10~7mol/L,荧蒽为2.2×10~(-7)mol/L。相对标准偏差小于3％。     

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.