Trace determination of nitrated polycyclic aromatic hydrocarbons using liquid chromatography with on-line electrochemical reduction and fluorescence detection

An efficient clean-up procedure coupled with a high performance liquid chromatography (HPLC) with on-line electrochemical (EC) reduction and fluorescence detection (FLD) was developed to quantify nitrated polycyclic aromatic hydrocarbons (NPAHs) in the airborne particulate. In this process, NPAHs were extracted ultrasonically followed by analysis by using a reversed phase column with an aqueous eluent containing 70% aqueous acetonitrile and sodium monocholoroacetate as a buffer solution. The extraction efficiencies were above 83% for 1-nitropyrene and 1,3-dinitropyrene (1,3-DNP) 1,6-DNP, and 1,8-DNP, and calibration graphs were linear with very good correlation coefficients (r>0.999) and the detection limits were in the range of 1.0-2.2 pg for dinitropyrenes and nitropyrene. The proposed method provides a relatively simple and convenient procedure for determining the NPAHs samples in airborne particulate.     

Catalytic oxidation of CO,hydrocarbons, and ethyl acetate over perovskite-type complex oxides

The catalytic activity of M^IM^IIO₃] perovskite-type complex oxides (M^I = La, Y, Nd, Yb; M^II = Co, Mn, Ni) in the oxidation of CO, propylene, benzene, ethylbenzene,o-xylene, and ethyl acetate was investigated. The Co-containing catalysts were shown to be more active in the oxidation than the Mn-containing catalysts. A relationship between the catalytic and adsorption properties was established.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 602–605, April, 1994.     

Fluorescence study of the solubilization of benzo[a]pyrene: application to its detection in coal washing waters

The solubilization of benzo[a]pyrene by organic solvents (dioxane, toluene and dichloromethane) and a surfactant (Triton X-100) was investigated. These media were successfully used for the determination of benzo[a]pyrene using fluorescence detection, with excellent limits of detection and large linear analytical ranges. Benzo[a]pyrene was detected in coal washing waters using liquid chromatography with fluorescence detection. The stability of this compound in dioxane was also examined.     

Synthesis and properties of new crystalline poly(arylene ether nitriles)

Crystalline poly(arylene ether nitrile) could be prepared by the polycondensation of 2,6-dihalobenzonitrile with resorcinol at 200°C in N-methylpyrrolidone in the presence of sodium carbonate. A reaction temperature of at least 200°C was necessary to attain high molecular weight polymer. Spectral data indicated that the polymer had the structure of a poly(meta-phenylene ether) with pendent nitrile groups on every other phenylene unit. Despite this structure, the crystallinity and the crystallization rate of the polymer were greater than those of the corresponding polymer with a para-linked structure. The glass transition temperature and the melting temperature of the polymer were almost the same as those of poly(etheretherketone) (PEEK^TM). A series of other new poly(arylene ether nitriles) were also examined. The polymers derived from 4,4′-biphenol, dihydroxytetra-phenylmethane, dihydroxydiphenylsulfone, and 1,5-isoquinolinediol had high glass transition temperatures. The poly(arylene ether nitriles) exhibited excellent tensile strength compared with the corresponding ketone- or sulfone-containing polymers. Comparing the three different kinds of polymers containing the same bisphenol units, the order of glass transition temperature was found to be sulfone- > nitrile- > ketone-containing polymers, while the order of tensile strength was nitrile- > ketone- > sulfone-containing polymers. The excellent mechanical properties are attributable to dipole-dipole interactions of nitrile groups. © 1993 John Wiley & Sons, Inc.     

Benzenoid Molecules with Uniform Distribution of π-Electrons within Rings

Summary. In a recent work it was demonstrated that in linear hexagonal chains the distribution of π-electrons into rings (as computed by means of the Randić–Balaban method) is uniform, irrespective of the nature of the terminal fragments. We now establish that an analogous, yet somewhat more complex, uniformity in the π-electron distribution exists also in double linear hexagonal chains, as well as in some other benzenoid systems.     

Procedures for the enhancement of selectivity in liquid phase chemiluminescence detection

An overview of liquid phase chemiluminescence (CL) processes is presented and the potential for CL detection in liquid chromatography (LC) is discussed, with particular reference to the luminol and peroxyoxalate reactions. Post column ion displacement from a solid phase reagent [a cation exchange resin in the copper(II) form] followed by catalysis of the luminol reaction is used for the quantification of mixtures of weak acids after separation by ion-exclusion chromatography. Polyaromatic hydrocarbons (PAHs) released during the combustion of biomass fuels are separated by reversed-phase chromatography and quantified by their sensitizing effect on the peroxyoxalate reaction. This procedure is also used for the determination of carboxylic acids in non-aqueous media after selective pre-column derivatization with a fluorescent label (9-anthracenemethanol).     

2-取代吡啶半菁染料的无溶剂微波合成及光谱性质的理论研究

在微波促进无溶剂条件下, 由N-甲基-2-甲基吡啶碘盐与取代芳香醛在哌啶作用下合成了一系列2-取代的吡啶半菁染料, 产物结构由元素分析, ¹H NMR, MS, IR, UV得到确认. 该方法操作简便, 收率高. 在此基础上, 对N-甲 基-2-(p-N,N-二甲氨基-苯乙烯基)吡啶半菁染料的光谱性质进行了理论计算.     

手性芳酰胺类分子钳的设计与微波合成

以间苯二甲酸为隔离基, 酰胺键桥联L-氨基酸甲酯构成手臂, 在微波辐射下合成了具有不同手性中心和裂穴的新型手性芳酰胺类分子钳. 结构均经¹H NMR, IR及元素分析确证, 并考察了其对芳香胺类化合物和D/L-氨基酸甲酯的识别性能. 初步研究表明, 这类分子钳受体不仅对中性小分子具有优良的识别性能, 其结合常数(K_a)可达2.66×10³ L•mol^－1, 而且对D/L-氨基酸甲酯亦具有良好的手性识别能力.     

Preparation and characterization of aliphatic/aromatic copolyesters based on 1,4-cyclohexanedicarboxylic acid

A series of biodegradable aliphatic/aromatic copolyesters, poly(butylene terephthalate)-co-poly(butylene cyclohexanedicarboxylate)-b-poly(ethylene glycol) (PTCG), were prepared by a two-step melt polycondensation method and characterized by means of GPC, FTIR, NMR, DSC, TGA, etc. The effects of aliphatic ester content on the physical, mechanical and thermal properties, as well as in vitro and in vivo degradation behaviors were investigated. The decrease in mechanical strength was observed with an increase in poly(butylene cyclohexanedicarboxylate) (PBC) molar fraction. DSC results showed one melting point and two glass transition temperatures in all samples, and the melting temperature was found to go down gradually as more cyclohexanedicarboxylic acid (CHDA) was added. During the in vitro and in vivo degradation processes, erosion of the surface was dominant as evidenced by scanning electron microscopic observations. The copolyesters containing many CHDA units were featured by the higher water uptake and faster degradation due to much richer amorphous phase within them.     

官能化蒙脱土负载双金属催化芳香氯化物水相脱氯

用PVP(聚乙烯吡咯烷酮)络合双金属Pd^2 ,Sn^4 后，再负载于用PEG400(平均分子量为400的聚乙二醇)官能化的蒙脱土上，制成双金属催化剂PVP—PdCl2-SnCl4/Montk10-PEG400,用于催化难溶于水的芳香卤化物水相脱卤，芳香族氮化物转化率达100％，该催化剂可重复使用。对催化剂进行了IR及TEM表征。