常见饮料中痕量铝的分光光度法研究

新试剂5-溴水杨基荧光酮可在pH5.5～6.8的六次甲基四胺缓冲溶液中,与铝,溴化十六烷基吡啶形成稳定的红色三元配合物。最大吸收波长约为568nm,摩尔吸光系数高达1.7×10~5L mol~(-1)·cm~1,常见金属离子很少干扰。据此,建立了测定微量铝的方法。其线性范围为0～6μg/25ml回收率在96％～103％之间。本文测定了常见饮茶,饮料及饮水中的微量铝。     

甲基膦酸二甲庚脂-HBr体系萃取色层法分离微量镉及其应用

本文提出了以 P350为固定相,硅胶为载体,1.0mol/L HBr 为流动相,采用水作洗脱液的萃取柱色层分离微量镉的新方法。研究了分离条件,萃取保留机理和干扰等。用制定的方法对铅锌矿和冶炼电转尘中微量镉进行了分离测定,均获得良好结果。回收率在95～102％之间。     

Photovoltaic and spectral properties of tetraphenyloporphyrin and metallotetraphenyloporphyrin dyes

Spectroscopical properties and photocurrent (or photovoltage) of tetraphenyloporphyrins and metallotetraphenyloporphyrins in nematic liquid crystal have been studied. Photoelectric response has been measured in an electrochemical cell made of the semitransparent semiconducting and golden electrodes with porphyrin dyes embedded in liquid crystal. Fluorescence, time-resolved luminescence in microsecond time scale and photoacoustic spectra have also been measured. The competition between radiative, non-radiative processes and charge transfer is discussed. It has been shown that effectivity of porphyrins for photocurrent generation depends on the presence/absence of central metal in the macrocycle of porphyrin skeleton and the kind of metal. The schematic model of the contributions of the dye molecule and semiconducting electrode in the electron transfer process is shown.     

A new stereoselective synthesis of 2-amino-4,5-dihydrothiophene-3-carbonitrile derivatives

A new stereoselective method for the synthesis of trans-isomers of 2-amino-4-aryl-5-benzoyl-4,5-dihydrothiophene-3-carbonitriles was proposed. The method involves base-catalyzed reactions of phenacyl thiocyanate with 3-(het)aryl-2-cyanoprop-2-enethioamides. (4R,5S/4S,5R)-2-Amino-5-benzoyl-4-(2-chlorophenyl)-4,5-ihydrothiophene-3-carbonitrile was structurally characterized by X-ray diffraction analysis. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1379–1383, July, 2007.     

Chemometric data analysis of pollutants in wastewater—a case study

In this study, chemometric techniques such as cluster analysis (CA), discriminant analysis (DA), principal component analysis (PCA) and partial least squares (PLS) were used to analyse the wastewater dataset to identify the factors which affect the composition of sewage of domestic origin, spatial and temporal variations, similarity/dissimilarity among the wastewater characteristics of cis- and trans-drains and discriminating variables. Samples collected from 24 wastewater drains in Lucknow city and from three sites on Gomti river in the month of January/February, May, August and November during the period of 5 years (1994-1999) were characterized for 32 parameters. The multivariate techniques successfully described the similarities/dissimilarities among the sewage drains on the basis of their wastewater characteristics and sources signifying the effect of routine domestic/commercial activities in respective drainage areas. Spatial and seasonal variations in wastewater composition were also determined successfully. CA generated six groups of drains on the basis of similar wastewater characteristic. PCA provided information on seasonal influence and compositional differences in sewage generated by domestic and industrial waste dominated drains and showed that drains influenced by mixed industrial effluents have high organic pollution load. DA rendered six variables (TDS, alkalinity, F, TKN, Cd and Cr) discriminating between cis- and trans-drains. PLS-DA showed dominance of Cd, Cr, NO₃, PO₄ and F in cis-drains wastewater. The results suggest that biological-process based STPs could treat wastewater both from the cis- as well as trans-drains, however, prior removal of toxic metals will be required from the cis-drains sewage. Further, seasonal variations in wastewater composition and pollution load could be the guiding factor for determining the STPs design parameters. The information generated would be useful in selection of process type and in designing of the proposed sewage treatment plants (STPs) for safe disposal of wastewater.     

Electroreductive polymerization of trans-[RuCl 2(vpy) 4] on Nd-Fe-B magnets: electrochemical impedance spectroscopy interpretation, Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy analysis

The electropolymerization of trans-[RuCl₂(vpy)₄] (vpy=4-vinylpyridine) monomer on Nd-Fe-B magnets was studied by electrochemical impedance spectroscopy (EIS). Impedance diagrams obtained during the polymerization process were used to monitor film formation. The EIS results gave insight into the electrochemical phenomena occurring at the magnet surface as the polymerization process progressed. The film structure and morphology were also studied by X-ray photoelectron spectroscopy, scanning electron microscopy and Raman spectroscopy. The Raman spectroscopy results showed that the polymerization takes place at the vinyl groups of the monomer and also that the redox polymer structure is very similar to that of the monomer. The ratio of the intensity of the XPS peaks for fluorine (from the electrolyte PF₆ ^–) and ruthenium present in the film showed that the polymer on Nd-Fe-B contained an equal proportion of Ru²⁺ and Ru³⁺, indicating that part of the film is positively charged, i.e. {[RuCl₂(vpy)₄]⁺} _n .     

An in situ STM study on the long-range surface restructuring of Au(1 1 1) in a non-chloroaluminumated ionic liquid

We report an in situ STM study of a potential-dependent long-range surface restructuring of Au(1 1 1) electrode in neat 1-butyl-3-methylimidazolium tetrafluoroborates (BMIBF₄) ionic liquid. Au(1 1 1) undergoes a significant long-range surface restructuring upon cathodic excursion to −1.0 V vs. Pt quasi-reference. The restructuring involves the formation of tiny pits, which then develops into a stable worm-like network with an average width of the network grids 2 nm. Electrochemical annealing occurs at the cathodic limit with the presence of a reduction product of cation BMI⁺. A smooth surface is recovered with the appearance of the typical (√3 × 22) reconstruction of Au(1 1 1). The surface restructuring is reestablished upon anodic excursion to −1.3 V after the adsorbed reduction product is oxidized. The long-range surface restructuring phenomenon is tentatively explained as a result of partial charge transfer to the weakly adsorbed BMI⁺, which reduces the metal–metal cohesive energy. In addition, the synergetic effect of the counter anion BF₄⁻ may also be involved. The results provide a knowledge of Au(1 1 1) electrode behavior in the neat ionic liquid and are beneficial to understanding in situ STM results involving surface morphological changes in such a media.     

Counterpoise-corrected potential energy surfaces of simple H-bonded systems

Geometries and stabilization energies of various simple H-bonded complexes (water dimer, hydrogen fluoride dimer, formamide dimer, formic acid dimer) have been determined by a gradient optimization that eliminates the basis set superposition error (BSSE) by the counterpoise (CP) method in each gradient cycle as well as by the standard gradient optimization. Both optimization methods lead to different potential energy surfaces (PES). The difference depends on the theoretical level used and is larger if correlation energy is considered. Intermolecular distances from the CP-corrected PES are consistently longer, and this difference might be significant (∼0.1 ?); also angular characteristics determined from both surfaces differ significantly. Different geometries were obtained even when passing to larger basis sets (aug-cc-pVDZ). The standard optimization procedure can result in a completely wrong structure. For example, the “quasi-linear” structure of the (HF)₂ (global minimum) does not exist at the standard MP2/ 6-31G** PES (where only cyclic structure was detected) and is found only at the CP-corrected PES. Stabilization energies obtained from the CP-corrected PES are always larger than these from the standard PES where the BSSE is added only a posteriori for the final optimized structure; both energies converge only when passing to a larger basis set (aug-cc-pVDZ). Received: 11 March 1998 / Accepted: 19 June 1998 / Published online: 4 September 1998 RID=" ID=" <E6>Acknowledgements.</E6> The project was supported by the Grant Agency of the Czech Republic (Grant No. 203/98/1166). RID=" ID=" <E5>Correspondence to</E5>: P. Hobza     

乙二醛双缩(2-羟基苯胺)(GBHA)在稀土离子分析中的应用

利用乙二醛双缩（2－羟基苯胺）（GBHA）对Ln^3 系离子进行分组分析，同时以GBHA为显色剂，用分光光度法分别测定了Ho^3 ,Yb^3 ,Er^3 ,Dy^3 和Tb^3五种离子，其检出限为10^-6mol/L，工作曲线线性范围为10^-5－－10^-3mol/L。     

Ab initio through‐space/bond interaction analysis of the long C–C bonds in Bi(anthracene‐9,10‐dimethylene) photoisomers

The bi(anthracene‐9,10‐dimethylene) photoisomer has remarkably long C–C single bonds. To examine the lengthening of the C–C bond, we propose a novel procedure for quantitatively analyzing orbital interactions in a molecule at the level of the ab initio molecular orbital method. In this procedure, we can cut off the specific through‐space/bond interactions in a molecule by artificially increasing the absolute magnitude of the exponents in a Gaussian function. Then, the spatial orbital interactions were perfectly cut off, and, each term that makes up the total energy, that is, the nuclear–electron attractions, the electron–electron repulsions, and the nuclear–nuclear repulsions cancel each other. Several model molecules of the photoisomer were analyzed by this procedure. It was found that the orbital interaction between the p orbital on the benzene ring and the σ* orbital on the C–C bond in question, σ→σ* electron transfer through π orbital, weakens the C–C bond efficiently when these orbitals were located in the “periplanar” conformation. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001