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81.
Bernaus A Gaona X Ivask A Kahru A Valiente M 《Analytical and bioanalytical chemistry》2005,382(7):1541-1548
The present work studies the adsorption behaviour of mercury species on different soil components (montmorillonite, kaolinite and humic acid) spiked with CH3HgCl and CH3HgOH at different pH values, by using XAS techniques and bacterial mercury sensors in order to evaluate the availability of methyl mercury on soil components. The study details and discusses different aspects of the adsorption process, including sample preparation (with analysis of adsorbed methyl mercury by ICP-OES), the various adsorption conditions, and the characterization of spiked samples by XAS techniques performed at two synchrotron facilities (ESRF in Grenoble, France and HASYLAB in Hamburg, Germany), as well as bioavailability studies using mercury-specific sensor bacteria. Results show that XAS is a valuable qualitative technique that can be used to identify the bonding character of the Hg in mercury environment. The amount of methyl in mercury adsorbed to montmorillonite was pH-dependent while for all soil components studied, the bond character was not affected by pH. On the other hand, clays exhibited more ionic bonding character than humic acids did with methyl mercury. This interaction has a higher covalent character and so it is more stable for CH3HgOH than for CH3HgCl, due to the higher reactivity of the hydroxyl group arising from the possible formation of hydrogen bonds.The bioavailability of methyl mercury adsorbed to montmorillonite, kaolinite and humic acids was measured using recombinant luminescent sensor bacterium Escherichia coli MC1061 (pmerBRBSluc). In case of contact exposure (suspension assays), the results showed that the bioavailability was higher than it was for exposure to particle-free extracts prepared from these suspensions. The highest bioavailability of methyl mercury was found in suspensions of montmorillonite (about 50% of the total amount), while the bioavailabilities of kaolinite and humic acids were five times lower (about 10%). The behaviour of methyl mercury in the presence of montmorillonite could be explained by the more ionic bonding character of this system, in contrast to the more covalent bonding character observed for humic acids. Thus, XAS techniques seem to provide promising tools for investigating the mechanisms behind the observed bioavailabilities of metals in various environmental matrices, an important topic in environmental toxicology. 相似文献
82.
83.
碘化物-结晶紫-聚乙烯醇体系分光光度法测定自来水中痕量二氧化氯 总被引:6,自引:0,他引:6
在稀磷酸介质中,二氧化氯(ClO2)氧化I离子形成 I3配阴离子,I3进一步与结晶紫(CV)阳离子形成离子缔合物[CV][I3」。在聚乙烯醇存在下,该离子缔合物最大吸收波长λmax位于552 nm处,摩尔吸光系数ε=25 × 105L·mol-1·cm-1,对 ClO2的检出限为 0.6 μg/L,线性范围是 0.6~280μg/L。加入适量 KF溶液可消除自来水中Fe(Ⅲ)的干扰。方法对μg/L级ClO2 的测定有较好的选择性,可成功地用于自来水样品分析。 相似文献
84.
Hiroshi Kojima Kosaku Sakeda Teijiro Ichimura Masao Takayanagi 《Journal of Molecular Structure》2003,655(1):185-190
Laser-induced fluorescence (LIF) excitation spectra of m-methylanisole in a supersonic jet were measured. Two series of progressions were observed in the spectrum, originating at 36048 and 36115 cm−1, which were successfully assigned to the transitions to the methyl internal rotational vibronic levels of the two isomers, i.e. cis and trans isomers, with the aid of hole-burning spectrum measurements and quantum-chemical calculations. The progression for the trans isomer was observed up to the 6a1 band, while only the 3a1 band in addition to the 0a1 and 1e bands was observed for the cis isomer. This finding can be explained by the conformational change upon the electronic excitation; the 60° rotation of the methyl torsional angle takes place for the trans isomer but not for the cis isomer. 相似文献
85.
A highly sensitive spectrophotometric method for the determination of nitrite in water and soil has been developed. The reaction of nitrite with acidified potassium iodide to liberate iodine which oxidizes leuco‐crystal violet (LCV) to form crystal violet having absorption maxima at 590 nm forms the bases of this method. In aqueous medium the system obeys Beer's law in the range of 0.1 to 1.0 μg per 25 mL (0.004–0.04 ppm), while in an extractive system the range is 0.025–0.25 μg in 100 mL (0.00025–0.0025 ppm). The molar absorptivity and Sandell's sensitivity were found to be 1.54 × 106 1 mol?1 cm?1 and 44 pg cm?2, respectively. 相似文献
86.
The kinetics of suspended emulsion polymerization of methyl methacrylate (MMA), in which water acted as the dispersed phase and the mixture of MMA and cyclohexane as the continuous phase, was investigated. It showed that the initial polymerization rate (Rp0) and steady-state polymerization rate (Rp) were proportional to the mass ratio between water and oil phase, and increased as the polymerization temperature, the potassium persulphate concentration ([I]) and the Tween20 emulsifier concentration ([S]) increased. The relationships between the polymerization rate and [I] and [S] were obtained as follows: Rp0 ∝ [I]0.73[S]0.32 and Rp ∝ [I]0.71[S]0.23. The above exponents were close to those obtained from normal MMA emulsion polymerization. It also showed that the average molecular weight of the resulting poly(methyl methacrylate) decreased as the polymerization temperature, [I] and [S] increased. Thus, MMA suspended emulsion polymerization could be considered as a combination of many miniature emulsion polymerizations proceeding in water drops and obeyed the classical kinetics of MMA emulsion polymerization. 相似文献
87.
In pH 6.0-11.2 Britton-Robinson buffer solution, binding of heparin with crystal violet (CV) can result in a significant enhancement of resonance Rayleigh scattering (RRS) and resonance non-linear scattering, such as frequency doubling scattering (FDS) and second-order scattering (SOS). Their maximum scattering wavelengths, λex/λem, appear at 492 nm/492 nm for RRS, 984 nm/492 nm for FDS and 492 nm/984 nm for SOS, respectively. The optimum conditions of the reaction, the influencing factors and the relationship between the three scattering intensities and the concentration of heparin have been investigated. New methods for the determination of trace amounts of heparin based on the RRS, FDS and SOS methods have been developed. The methods exhibit high sensitivities, the detection limit for heparin is 2.9 ng ml−1 for the RRS method, 3.5 ng ml−1 for the FDS method and 3.3 ng ml−1 for the SOS method. The methods have good selectivity and were applied to the determination of heparin in heparin sodium injection samples with satisfactory results. 相似文献
88.
近年来亚硝酸甲酯分子(CHa0NO)的光解动力学研究十分活跃{‘5],主要集中在紫外激光的单光子解离的机理,光解过程的矢量相关性质和光解产物的态分布.CH30NO分子的解离能D。(CH30-NO)=174kJ·mol‘,若单从能量上看,人<689。的光就能使其解离,但人>400urn的光解离研究还未见报导.*H30*0分子在人>40onm的强激光场下是充电离还是先解离,是单光子解离还是多光子解离,以及通过哪个电子态解离都不清楚.时间飞行质谱不仅具有质量分辨率高、范围宽,而且响应快,因此适合做光解光电离过程初生态产物的探测.特别是时间飞… 相似文献
89.
A new CoW11Mn/PANI/TiO2 ternary composite was synthesized with K8[Co(H2O)MnW11O39] (CoW11Mn) and PANI/TiO2 by electrostatic self-assembly. These catalysts were characterized using infrared (IR) spectroscopy, X-ray diffraction, scanning electron microscopy, ultraviolet–visible spectroscopy, and N2 adsorption–desorption. CoW11Mn/PANI/TiO2 was used to photodegradate the example contaminant, gentian violet (GV). Under the optimum photodegradation conditions, 92.63% degradation was achieved, indicating that the introduction of polyoxometalate and polyaniline greatly enhanced the photocatalytic performance of the catalyst. Moreover, CoW11Mn/PANI/TiO2 exhibits stable performance with little loss in activity after three successive runs. Thus, CoW11Mn/PANI/TiO2 ternary composite could be a promising photocatalyst in photodegradation of organic pollutants. 相似文献
90.
The first total synthesis of isoquinolinone alkaloid marinamide 1 and its methyl ester 2 was described. The key steps involved a regioselective Frieclel-Crafts reaction of 1-benzyl-1H-pyrrole to form the intermediate 8. 相似文献