Simultaneous determination of bromide and nitrate in contaminated waters by ion chromatography using amperometry and absorbance detectors

This study describes a new ion chromatography method using a low-capacity anion exchange column with amperometric and absorbance detection for rapid and simultaneous determination of Br⁻ and NO₃⁻ in contaminated waters where one of these ions is present in excess compared to other. The use of two detectors overcomes the problem of baseline separation for Br⁻ and NO₃⁻ for accurate quantification, which was commonly encountered when using a low-capacity anion exchange column and suppressed conductivity detection mode. The method achieved accurate quantification of these two ions without requirement of baseline separation. The accuracy of 2.8% for NO₃⁻ was determined using a quality control sample obtained from UN GEMS/Water PE Study No. 6. The detection limits for Br⁻ and NO₃⁻ were 20 and 6 μg l⁻¹ (25 μl sample), respectively. Linearity of these two ions was over three orders of magnitude with a correlation coefficient >0.998. The influence of potential interfering ions was also studied followed by the determination of Br⁻ and NO₃⁻ in seawater, unsaturated zone water, soil extract and groundwater.     

油田采出液中微量羧酸盐表面活性剂分析方法研究

油田采出液中化学剂浓度的检测是三元复合驱动态评价的重要指标之一。本文针对现场提出的对微量羧酸盐表面活性剂的检测问题,建立了一种用紫外分光光度法测定微量羧酸盐表面活性剂分析的新方法。该法简便、准确快速,线性范围宽,回收率在94.4-103.1%之间,相对标准偏差为1.38%。并根据油田生产的实际情况,探论了碱、聚合物、原油等干扰因素对测定的影响,结果满意。     

巯基/乙烯基硅氮烷紫外光固化的研究

利用原位红外跟踪技术和光-示差扫描量热技术研究了不同类型多官能巯基化合物与乙烯基硅氮烷的紫外光聚合动力学过程.结果表明,巯基化合物官能度越高,聚合反应速率越高,但最终转化率越低.巯基丙酸酯类化合物比烷基硫醇类化合物更易与乙烯基硅氮烷反应.在较低温度下,反应温度对聚合反应的影响较弱,反应活化能约为2.3kJ/mol,而较高反应温度下反应速率偏离Arrhenius方程.     

Optimization of hydroxyl radical formation using TiO2 as photocatalyst by response surface methodology

The determination of the optimum parameters for hydroxyl radicals (OH) formation by a TiO₂ solution has been investigated by measuring the emitted fluorescence after the reaction with terephthalic acid has occurred. After UV irradiation, the terephthalic acid was transformed into 2-hydroxyterephthalic acid whose fluorescence is directly proportional to the generated OH. Optimization of hydroxyl radicals’ formation using TiO₂ as catalyst was carried out by studying the effects of irradiation time, TiO₂ concentration and terephthalic acid concentration on the production of the fluorescent HTA with an experimental design. The aim of our research was to apply response surface methodology as a chemometric method for the optimization of the reaction conditions. The combination of irradiation time, TiO₂ concentration and terephthalic acid concentration was varied at designed points of a central composite rotatable design. The three factors were found to have a significant effect upon the reaction. The optimum conditions for the reaction achievement were estimated to be 10 min for the irradiation time, 25 μg mL⁻¹ TiO₂ concentration and 0.1 mmol L⁻¹ terephthalic acid concentration. Afterwards, using these parameters the method was applied for the determination of the ability of several plant extract samples to scavenge the formed OH.     

邻苯二甲酸在苯并三氮唑银为银源的光敏热显影体系中的作用

本文研究了邻苯二甲酸(H₂PA)的用量以及H₂PA的阴离子和阳离子对以苯并三氮唑银为银源的光敏热显影体系的影响.结果表明,在苯并三氮唑银体系中,邻苯二甲酸(H₂PA)的阳离子(H⁺)降低了体系的pH值,还原剂的显影活性和H₂PA与银离子的络合能力;而其阴离子(PA^2-)则与苯并三氮唑银生成中间体,起到传输银离子的作用.     

Azocoupling reaction of 1-benzyl-3,4-dihydroisoquinolines with diazonium salts and the properties of its products

It has been shown that drotaverine base and 1-benzyl-3,3-dimethyl-3,4-dihydroisoquinoline react with diazonium salts to form hydrazones. The position of the K-band in the UV spectra of the compounds obtained depends on the nature of the substituenst in the aromatic ring and the absorption frequency correlates with its Hammett constant. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 246–251, February, 2008.     

Characterization of self‐assembled phenyl and benzyl isothiocyanate thin films on Au surfaces

Structures of self‐assembled monolayers (SAMs) prepared from benzyl isothiocyanate (BZIT) and phenyl isothiocyanate (PHIT) were comparatively investigated by means of surface enhanced Raman scattering (SERS) on gold nanoparticle surfaces. Both the molecules are assumed to have upright geometries binding via the sulfur atom, from the SERS spectral features. The broad and split bands at ～2100 cm^?1 could be ascribed to the combination band ν_9a + ν₁₂ of the phenyl ring vibrations through a Fermi‐resonance interaction with the ν₃(NCS) band in the neat‐liquid state. Such broad bands became quite symmetric upon adsorption on Au. UV‐vis absorbance spectroscopy and cyclic voltammetry (CV) were used to compare the kinetics of the formation of SAMs on gold. Our results suggest that BZIT should have a relatively faster self‐assembly than PHIT, as indicated from signal decrease in the CV graph, which suggests a more vertical stance for BZIT in line with Raman measurements. Copyright © 2006 John Wiley & Sons, Ltd.     

Effects of solar UV irradiation on the tensile properties and structure of PPTA fiber

This paper comprehensively studied the effects of simulated solar ultraviolet irradiation on the mechanical and structural properties of the Twaron2000 para-aramid fiber by use of mechanical test, SEM, XRD, DSC, DMA and ATR-IR measurements. The results showed that after UV irradiation, the mechanical properties of the fiber were decreased obviously, and UV irradiation deteriorated the surface and defect areas of the fiber severely by photo-induced chain scission and end group oxidation in air with the crystalline structure remained almost unchanged although some local rearrangement of the crystalline area might occur. It was found that surface etching and shortening of the crystalline correlation length along the fiber axis were the main causes of the mechanical loss induced by UV irradiation.     

Modelling light stabilizers as thermal antioxidants

Light stabilizers often display some degree of antioxidant activity against thermal degradation of polymers both in the solid state and the melt. Although this capacity to date has been documented in some instances such features have not been kinetically modelled for many light stabilizers. An understanding of the mechanisms of this activity is crucial in polymer materials due to the close link between prior thermal behaviour and post stabilisation.This paper considers the potential antioxidant activity of three representative UV stabilizers using a model system initiated (2,2′-azo-bisisobutyronitrile, AIBN) cumene oxidation. Kinetic measurements of oxidation rates in the presence of the stabilizers showed that the antioxidant activity as well as the mechanism and mode of inhibition was different for each of the stabilizers. Thus, whilst a triazine UV absorber (Cyasorb UV 1164) did not display any antioxidant activity, a hindered phenol (Cyasorb UV 2908) operated as a peroxy radical acceptor, and a hindered amine (Cyasorb 3529) retarded the model reaction without an induction period like many HAS stabilizers.The Cyasorb 2908 revealed weak antioxidant activity with a rate constant for the addition of cumylperoxy RO₂ radicals to the functional group of the stabilizer k₇ = 10^6.2±0.1 e^{−(3900±600)/RT}, however, the inhibition index f (80 °C) is significantly higher than that of the commercial phenolic antioxidant Irganox 1076. Oxidation rate profiles in the presence of Cyasorb 3529 displayed a strong retarding activity by the stabilizer under conditions of the model experiments. The rates were found to depend linearly on the reciprocal square root of the concentration of the stabilizer over a sufficiently wide range thereby fitting the mechanism for the addition of cumylalkyl R radicals to the Cyasorb molecules. The rate constants for the addition of cumyl R radicals to the Cyasorb were determined to be k_(333-353 K) = (2.0 ± 0.8) × 10⁸ M⁻¹ s⁻¹. This value surpasses even the rate constants for other related HAS Chimassorb [Zeynalov EB, Allen NS. Effect of micron and nano-grade titanium dioxides on the efficiency of hindered piperidine stabilizers in a model oxidative reaction. Polym Degrad Stab 2006;91(4):931-9.] stabilizers and it follows that Cyasorb 3529 is a powerful retarder of thermal oxidation.     

Correlating Pressure‐Induced Emission Modulation with Linker Rotation in a Photoluminescent MOF

Conformational changes of linker units in metal‐organic frameworks (MOFs) are often responsible for gate‐opening phenomena in selective gas adsorption and stimuli‐responsive optical and electrical sensing behaviour. Herein, we show that pressure‐induced bathochromic shifts in both fluorescence emission and UV/Vis absorption spectra of a two‐fold interpenetrated Hf MOF, linked by 1,4‐phenylene‐bis(4‐ethynylbenzoate) ligands ( Hf‐peb ), are induced by rotation of the central phenyl ring of the linker, from a coplanar arrangement to a twisted, previously unseen conformer. Single‐crystal X‐ray diffraction, alongside in situ fluorescence and UV/Vis absorption spectroscopies, measured up to 2.1 GPa in a diamond anvil cell on single crystals, are in excellent agreement, correlating linker rotation with modulation of emission. Topologically isolating the 1,4‐phenylene‐bis(4‐ethynylbenzoate) units within a MOF facilitates concurrent structural and spectroscopic studies in the absence of intermolecular perturbation, allowing characterisation of the luminescence properties of a high‐energy, twisted conformation of the previously well‐studied chromophore. We expect the unique environment provided by network solids, and the capability of combining crystallographic and spectroscopic analysis, will greatly enhance understanding of luminescent molecules and lead to the development of novel sensors and adsorbents.