A new room temperature ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate as a solvent for extraction and preconcentration of mercury with determination by cold vapor atomic absorption spectrometry

A new room temperature ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate abbreviated as [C₄tmsim][PF₆] was synthesized and developed as a novel medium for liquid/liquid extraction of inorganic mercury in this work. Under optimal condition, o-carboxyphenyldiazoamino-p-azobenzene abbreviated as CDAA reacted with inorganic mercury to form a neutral Hg-CDAA complex, the complex was rapidly extracted into ionic liquid phase. After back-extracting into aqueous phase with sulfide sodium solution, the mercury concentration was detected by cold vapor atomic absorption spectrometry. The extraction and back-extraction efficiencies were 99.9 and 100.1% for 5.0 μg L⁻¹ standard mercury in 1000 mL of water solution, respectively. The detection limit, calculated using three times the standard error of estimate of the calibration graph, is 0.01 ng of mercury per milliliter water sample. The proposed method has been used to the determination of trace inorganic mercury in natural water with satisfactory results. Moreover, Zeta potential and surface tension of [C₄tmsim][PF₆] solution were measured and applied to explain the extraction mechanism of [C₄tmsim][PF₆] system.     

Conductivity of solvated electrons in hexane investigated with terahertz time-domain spectroscopy

We present investigations of the transient photoconductivity and recombination dynamics of quasifree electrons in liquid n-hexane and cyclohexane performed using terahertz time-domain spectroscopy (THz-TDS). Quasifree electrons are generated by two-photon photoionization of the liquid using a femtosecond ultraviolet pulse, and the resulting changes in the complex conductivity are probed by a THz electromagnetic pulse at a variable delay. The detection of time-domain wave forms of the THz electric field permits the direct determination of both the real and the imaginary part of the conductivity of the electrons over a wide frequency range. The change in conductivity can be described by the Drude model, thus yielding the quasifree electron density and scattering time. The electron density is found to decay on a time scale of a few hundred picoseconds, which becomes shorter with increasing excitation density. The dynamics can be described by a model that assumes nongeminate recombination between electrons and positive ions. In addition, a strong dependence of the quasifree electron density on temperature is observed, in agreement with a two-state model in which the electron may exist in either a quasifree or a bound state.     

Sensitive Determination of Cyanide in Cigarette Smoke by Capillary GC with a MicroECD

A sensitive method using capillary gas chromatography coupled with a micro electron capture detector (μECD) has been developed for the determination of cyanide in cigarette smoke. The procedure is based upon the conversion of cyanide to cyanogen chloride by chloramine-T. Cyanogen chloride, dissolved in n-hexane, was analyzed by GC–μECD. Under optimum conditions, the detector response was linear from 25.0 ng mL^?1 to 15.0 μg mL^?1 with relative standard deviation between 0.07 and 3.30%. Recovery ranged from 86.0 to 116.0%. The method was shown to be precise, accurate and linear over the range of concentration of analytes.     

Bandunamide, a Novel Cyclopeptide from the Streptomyces Griseovariabilis bandungensis

A new cyclic octapeptide, bandunamide, was isolated from the acetone extracts of streptomyces griseovariabilis bandungensis. This cyclic octapeptide exhibits strong antimicrobial activity against Phytophthora drechsleri (IC50=15 ng/mL), Colletotrchum higginsiannum(IC50=15.6 ng/mL), Piricularia oxyzae (IC50=0.2 μg/mL), and Fusarium oxysporum f. Sp.(IC50= 100μg/mL). The structure elucidation of bandunamide is herein reported.     

用高分辨率电感耦合等离子体-原子发射光谱仪测定高纯铬中的杂质元素

本文报道了高分辨率、高灵敏度的顺序扫描型电感耦合等离子体原子发射光谱仪(ICPS-8100)在高纯物质分析中的应用。对元素分析线进行优化选择;采用轴向观测方式,对高纯铬中μg/g级的杂质元素As、Sn、Sb、Pb进行直接同时测定,分析结果令人满意。     

序加实验理论模型误差修正的研究

针对序进应力加速实验理论模型中数学算法的误差,提出一种新的计算模型,新模型利用计算机编程辅助计算,显著地减小了模型误差.利用新、旧模型算法对理论数据进行计算,表明原模型算法存在13%以上的激活能计算误差以及150%以上的寿命计算误差（Q≤10　eV）,而新模型算法可以将激活能误差控制在1%以内,寿命计算误差控制在-41%以内.     

A modified image enhancement algorithm based on color constancy

According to the color constancy theory, a modified variation Retinex is proposed for improving the visibility of the dark regions in images under insufficient and/or non-uniform lighting conditions. A new penalty functional based on nonlinear diffusion and correlation between the reflectance and the given image is designed for the intensity image enhancement, followed by adaptive color compensation. With high computational efficiency achieved by an improved multi-resolution algorithm, simulation results prove that the proposed method shows more colorful and vivid visual performance, and achieves wider dynamic range with higher objective standard values.     

Syntheses and oxidation of methyloxorhenium(V) complexes with tridentate ligands

Four new methyloxorhenium(V) compounds were synthesized with these tridentate chelating ligands: 2-mercaptoethyl sulfide (abbreviated HSSSH), 2-mercaptoethyl ether (HSOSH), thioldiglycolic acid (HOSOH), and 2-(salicylideneamino)benzoic acid (HONOH). Their reactions with MeReO(3) under suitable conditions led to these products: MeReO(SSS), 1, MeReO(SOS), 2, MeReO(OSO)(PAr(3)), 3, and MeReO(ONO)(PPh(3)), 4. These compounds were characterized spectroscopically and crystallographically. Compounds 1 and 2 have a five-coordinate distorted square pyramidal geometry about rhenium, whereas 3 and 4 are six-coordinate compounds with distorted octahedral structures. The kinetics of oxidation of 2 and 3 in chloroform with pyridine N-oxides follow different patterns. The oxidation of 2 shows first-order dependences on the concentrations of 2 and the ring-substituted pyridine N-oxide. The Hammett analysis of the rate constants gives a remarkably large and negative reaction constant, rho = -4.6. The rate of oxidation of 3 does not depend on the concentration or the identity of the pyridine N-oxide, but it is directly proportional to the concentration of water, both an accidental and then a deliberate cosolvent. The mechanistic differences have been interpreted as reflecting the different steric demands of five- and six-coordinate rhenium compounds.     

千层塔挥发油成分的气相色谱-质谱法(GC/MS)分析

通过将千层塔挥发油经气相色谱-质谱法(GC/MS)分析,首次研究其化学成分.结果表明:千层塔挥发油成分复杂,含量较高的为3-羟基-2-甲基戊二酸二甲酯、苹果酸二甲酯、3-羟基-正丁酸甲酯、3-(4-羟苯基)-2-丙烯酸甲酯与4-羟基-α,α,4-三甲基-环己甲醇.此外,还鉴别到一种石松生物碱.千层塔挥发油中分子量较小的酯类与醇类物质较多,并含有一种生物碱Luciduline.     

Synthesis, Crystal Structure and Thermal Property of a Manganese(II) 4-Carboxyphenoxyacetate Complex

1 INTRODUCTION Organic aromatic carboxylic acids which com-monly possess multiple coordination modes are ex-cellent candidates for constructing supramolecularmetal complexes[1～6]. 4-Carboxyphenoxyacetic acid(4-CPOAH2), widely used in biological activitystudies, is a multidentate flexible ligand that not onlyhas versatile binding possibilities but also can formregular hydrogen bonds as both hydrogen-bond donorand acceptor. However, there have been few reportson the coordination chemistr…