新型水蒸气顶空富集装置在饮用水中痕量挥发性有机物非目标筛查中的应用

以饮用水中痕量挥发性有机物(VOCs)非目标筛查为目的,构建了一种新型的大体积水样高倍富集装置。对其精馏管长度、回收冷凝液体积、吸收介质等影响富集效果的关键因素进行了优化。该装置以水蒸气为吹扫气,同时以水作为吸收剂,将1 L水样富集浓缩至5 mL后,可使原有吹扫捕集-气相色谱-质谱法(P&;T-GC-MS)分析VOCs的灵敏度提高1～2个数量级。用该方法对某净水厂的源水与出厂水进行了痕量VOCs的定性分析与比较。与传统P&;T-GC-MS方法相比,本方法对两种水样的污染物检出数目由原来的无检出和5种分别提高至16种和35种。分析结果表明饮用水消毒前后污染物的种类及含量存在显著差异。     

90Sr in lake sediments

For a better understanding of the behaviour of⁹⁰Sr in aquatic systems, this -emitter has been determined in the different layers of a lake sediment core which has been previously dated using the well established²¹⁰Pb dating method. For this, a radiochemical technique has been developed for the isolation of strontium from the sediment samples and for its activity measurement with a low-level gas-flow proportional counter. A conservative behaviour of⁹⁰Sr in the water column remaining dissolved in the water body, can be inferred from the data obtained. Consequently, a possible⁹⁰Sr transport pathway through the outflowing waters of the lake can be deduced.     

An organic solvent-free microwave-assisted extraction of some priority pollutants of phenols in lake sediments.

Alkaline water was used for the microwave-assisted extraction of some priority pollutants of phenols in sediments, i.e. phenol (Ph), 2-chlorophenol (2CP), 2,4-dichlorophenol (2,4DCP), 4-chlorophenol (4CP), 4-dinitrophenol (4NP) and pentachlorophenol (PCP). This organic solvent-free extraction procedure was optimized by studying the parameters such as pH, volume of the alkaline water, extraction pressure and time. Under the optimized conditions, the recoveries of phenols were in the range of 80% to 110%. The extracts were then cleaned-up and concentrated by microcolumn solid phase extraction (SPE) and determined by gas chromatography-flame ionization detection system. The relative standard deviation of the overall-method for most phenol determinations was about 5.0% (n = 6). The proposed method, which needs little volume (1 mL) of ethanol for SPE, has been applied to determine these phenols in sediment samples, and the analytical results are in good agreement with those achieved by Soxhlet extraction.     

Radiocesium sorption-desorption processes in lake sediments

The kinetics of radiocesium sorption and desorption by cation solutions and the corresponding radiocesium distribution profiles in sediment cores were investigated. The results have shown that a significant percentage of radiocesium is adsorbed in the sediments during the first 3 d. Radiocesium reaches rapidly (< than 5 d) at a depth which does not exceed 3.5 cm. The desorption of radiocesium was found to depend on cation concentrations. Empirical laws are derived both for cesium adsorption and desorption.     

Modern approaches to chemical toxicity screening

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Sorption characteristics and mechanisms of organic contaminant to carbonaceous biosorbents in aqueous solution

A series of carbonaceous biosorbents was prepared by pyrolyzing pine needles,a model biomass,at various temperatures (100-700℃) under an oxygen-limited condition for 6h. The elemental composi-tions and the specific surface areas (BET-N2) of the biosorbents were analyzed. Sorption properties of 4-nitrotoluene to the biosorbents and their mechanisms were investigated,and then correlated with the structures of the biosorbents. The result shows that with the increase of the pyrolytic temperature,the aromaticity of the carbonaceous biosorbents increases dramatically and the polarity (the (N O)/C atomic ratio) decreases sharply. Correspondingly,conformations of the organic matter in the biosor-bents transform gradually from a "soft-state" to a "hard-state" and the specific surface areas of the resultant biosorbents extend rapidly. The sorption isotherms fit well with the Freundlich equation. The regression parameters (i.e.,N and lgKf) are linearly related to the aromaticity indices (the H/C atomic ratio). Contributions of adsorption and partition to total sorption of the carbonaceous biosorbents are quantified. The adsorption of the carbonaceous biosorbents increases quickly with the increase of the pyrolytic temperature. The saturated adsorption amounts (Qmax) increase linearly with the increase of the specific surface areas (SA) of the biosorbents. For the carbonaceous biosorbents with hard-state carbon,the calculated normalized-Qmax values by SA are comparable to the theoretical estimation (2.45 μmol/m2). In comparison,for the carbonaceous sorbents with soft-state carbon,the calculated nor-malized-Qmax values by SA are much higher than the theoretical estimation. The partition coefficients (Kom) increase with the decrease of the polarity of the biosorbents,reaching a maximum,and then de-crease sharply with further decreasing the polarity,suggesting that partition mechanism be dominated by the compatibility and accessibility of the sorbent medium with organic pollutant. These observations will provide a theoretical and practical reference to design a cost-effective and high-efficient sorbent,and to accurately predict sorption properties and mechanisms of a given sorbent.     

Sorption of organic dyes of various molecular weights on mineral sorbents and on sea and lake bottom sediments

The sorption of organic dyes of various molecular weights (from 100 to 700 amu) from aqueous solutions on minerals and on sea and lake bottom sediments was studied.     

Combining different analytical approaches to identify odor formation mechanisms in polyethylene and polypropylene

In a previous study, we identified carbonyls as highly odor-active compounds in both unprocessed and processed polypropylene (PP) with higher intensities after processing, indicating a temperature-driven forming mechanism. In the presented work, we studied whether (a) these carbonyls are the major odor drivers to the overall odor of polyolefins, (b) their formation is taking place already at moderate temperatures well below the typical processing temperatures, (c) conventional antioxidants in polyolefins can prevent or reduce their formation, and (d) whether reducing the amount of oxygen present can decrease the overall odor. One polyethylene (PE) and one PP were selected, and both stabilized and unstabilized polymer powder samples were exposed to conditions differing in oxygen concentration and aging time. The changes in the volatile fraction as well as the formation of odor-active compounds were monitored using a multidisciplinary approach by combining analytical methods based on gas chromatography (GC), multivariate data analysis, and sensory methods (GC–olfactometry and a sensory panel). Both investigated materials (PE and PP) showed similar degradation products (aldehydes, ketones, carboxylic acids, alcohols, and lactones) which increased dramatically with increasing aging time and the lack of stabilization. Oxidation products, mainly carbonyl compounds, were responsible for the odor of the investigated materials. The main odor drivers were unsaturated ketones and aldehydes with a chain length between six and nine C-atoms. Interestingly, similar odor patterns were found for both stabilized and unstabilized samples, indicating that similar formation processes take place independent of the stabilization.     

HREELS to identify electronic structures of organic thin films

The electronic structure of -oligothiophene (nT) thin films has been investigated for increasing chain lengths of n=4–8 thiophene units with high resolution electron energy loss spectroscopy (HREELS) in the specular reflection geometry at a primary energy of 15 eV. The great advantage of this technique in contrast to UV/VIS absorption spectroscopy results from the fact, that the impact scattering mechanism of HREELS makes it possible to also detect optically forbidden electronic transitions. On the other hand, the electrons used as probes in HREELS have a wavelength which is two orders of magnitudes smaller if compared to those of photons used in UV/VIS absorption spectroscopy. Therefore individual molecules are excited by HREELS independent from each other and hence the excitation of collective excitons is not possible. As a result, information about the orientation of the molecules cannot be achieved with HREELS, which, however, is possible in polarization-dependent UV/VIS spectroscopy.     

Determination of inositol phosphate esters in lake sediments

A procedure for the determination of the total inositol polyphosphate content of lake sediments is presented and evaluated. This technique involves extraction with NaOH, cleanup of the extract, and isolation and identification of two groups of inositol phosphate esters by ion-exchange chromatography. Radioisotope dilution is employed to correct for losses during the extraction, cleanup and isolation steps. Recoveries of the radiotracer inositol phosphates have averaged 85% during the analysis of approximately 40 calcareous and non-calcareous sediment samples and more than 20 soil samples.     

HREELS to identify electronic structures of organic thin films

The electronic structure of alpha-oligothiophene (alphanT) thin films has been investigated for increasing chain lengths of n= 4-8 thiophene units with high resolution electron energy loss spectroscopy (HREELS) in the specular reflection geometry at a primary energy of 15 eV. The great advantage of this technique in contrast to UV/VIS absorption spectroscopy results from the fact, that the impact scattering mechanism of HREELS makes it possible to also detect optically forbidden electronic transitions. On the other hand, the electrons used as probes in HREELS have a wavelength which is two orders of magnitudes smaller if compared to those of photons used in UV/VIS absorption spectroscopy. Therefore individual molecules are excited by HREELS independent from each other and hence the excitation of collective excitons is not possible. As a result, information about the orientation of the molecules cannot be achieved with HREELS, which, however, is possible in polarization-dependent UV/VIS spectroscopy.     

气相色谱-质谱-自动质谱解卷积技术在沉积物和污泥中有机污染物非靶标筛查中的应用

以沉积物和污泥中非极性和弱极性有机污染物的非靶标筛查为目的,建立了一种超声波辅助提取-气相色谱-质谱结合自动解卷积技术的筛查方法。以二氯甲烷为溶剂超声波辅助提取样品3次,每次20 min,提取液经凝胶渗透色谱(GPC)和硅胶层析柱净化,再用3 g铜粉超声10 min除硫。前处理方法的重复性(RSD, n=5)为5.8%~14.9%。采用自动质谱解卷积软件(AMDIS)和标准谱库定性鉴别出所含的有机物。在两类样品中共鉴别出290种有机污染物,其中沉积物样品中190种,污泥样品中153种。鉴别出的污染物包括美国环境保护署(EPA)优先控制污染物、药物和除草剂等新型污染物、抗氧化剂、中间体、有机溶剂及化工原料等。该方法灵敏度高,重复性好,可用于复杂基质样品中有机污染物的非靶标筛查。     

Novel approaches to the analysis of steroid estrogens in river sediments

A wide range of estrogenic contaminants has been detected in the aquatic environment. Among these, natural and synthetic steroid estrogens, typically present in municipal sewage-treatment plant (STP) effluents, are the most potent. In this study a new GC–MS method has been developed for direct analysis of five major steroid estrogens (estrone, 17β-estradiol, 17α-ethinylestradiol, dienestrol, and diethylstilbestrol) in river sediments. Four GC–MS systems used for analysis of underivatized analytes in purified extracts were compared. Relatively low detection limits (1.5–5 ng g⁻¹ dried sediment) and good repeatability of GC splitless injection (RSD 1–2%) were achieved by use of a system combining low-pressure gas chromatography with a single-quadrupole mass analyzer (LP-GC–MS). Use of orthogonal gas chromatography (GC×GC) hyphenated with high-speed time-of-flight mass spectrometry (HSTOF-MS) enabled not only significantly better resolution of target analytes, and their unequivocal identification, but also further improvement (decrease) of their detection limits. In addition to these outcomes, use of this unique GC×GC–TOF-MS system enabled identification of several other non-target chemicals, including pharmaceutical steroids, present in purified sediment extracts.     

Application of the high-resolution low temperature spectrofluorometry to analysis of PAHs in lake sediments, marine intertidal sediments and organisms

Summary This study presents an application of high-resolution low temperature spectrofluorometry (Shpol'skii effect) to quantitative analysis of PAHs in lake sediments, marine intertidal sediments and marine organisms. The main characteristics of the analytical computerized set-up are developed and show the selectivity, the sensitivity and the high speed of the experimental procedure, necessary for routine analysis of hydrocarbon traces. A correlation assay between PAHs distribution in sediments of an Alpine lake and that determined in vehicle exhaust emissions weighted from the accurate representation of the total number of passenger cars in France has been studied. We also present an investigation of concentration profiles and PAHs distributions in intertidal sediments and biota bivalves in the Gulf of Kuwait.     

Evaluation of extraction approaches linked to ELISA and HPLC for analyses of microcystin-LR, -RR and -YR in freshwater sediments with different organic material contents

The efficiencies of conventional extraction techniques and analytical methods (HPLC–DAD and ELISA) were investigated for analyses of microcystins (MCs) in sediments. Our results showed several limitations. First, the extraction efficiency strongly depends on the extraction solvent, and extraction with 5% acetic acid in 0.2% trifluoroacetic acid (TFA)–methanol was confirmed as being the most appropriate for three different sediments (recovery: 33.1–44.9% of total MCs according to HPLC analyses). Second, the recovery of MCs was affected by the type of sediment but did not clearly correlate with the content of organic carbon. These results suggest that the sorption of MCs onto inorganic materials such as clay minerals is probably a more important process than interactions of the MCs with organic sediment matter. Third, the structure of the MCs is another crucial factor that affects the sorption of MCs and their recovery from sediments. Hydrophilic MC-RR gave much lower recoveries (20.0–38.8%) than MC-YR (44.1–59.5%) or MC-LR (55.3–77.8%) from three different types of spiked sediments. Recovery results analysed with HPLC–DAD correlated well with ELISA analyses. Further, extraction with 5% acetic acid in 0.2% TFA–methanol was used for analyses of MCs in 34 natural sediment samples collected from Brno reservoir (Czech Republic) from April to October 2005. Concentrations of MCs in sediments ranged from 0.003 to 0.380 μg/g sediment d.m. (ELISA results) or 0.016–0.474 μg/g d.m. (HPLC results). These values are equivalent to 0.63–96.47 μg/L of sediment (ELISA) or 4.67–108.68 μg/L (HPLC), respectively. Concentrations of sediment MCs showed both temporal and spatial variability, with the highest MC contents observed in the spring (April and May) and the lowest concentrations in July and August. Our results demonstrate the suitability of the methods described here for studying the occurrence, fate and ecological role of MCs in the aquatic environment.      

Tuning the stability of organic radicals: from covalent approaches to non-covalent approaches

Organic radicals are important species with single electrons. Because of their open-shell structure, they are widely used in functional materials, such as spin probes, magnetic materials and optoelectronic materials. Owing to the high reactivity of single electrons, they often serve as a key intermediate in organic synthesis. Therefore, tuning the stability of radicals is crucial for their functions. Herein, we summarize covalent and non-covalent approaches to tune the stability of organic radicals through steric effects and tuning the delocalization of spin density. Covalent approaches can tune the stability of radicals effectively and non-covalent approaches benefit from dynamicity and reversibility. It is anticipated that the further development of covalent and non-covalent approaches, as well as the interplay between them, may push the fields forward by enriching new radical materials and radical mediated reactions.

Covalent and non-covalent approaches to tune the stability of organic radicals through steric effects and the delocalization of spin density.     

Genetic and genomic approaches to identify and study the targets of bioactive small molecules

Natural and synthetic bioactive small molecules form the backbone of modern therapeutics. These drugs primarily exert their effect by targeting cellular host or foreign proteins that are critical for the progression of disease. Therefore, a crucial step in the process of recognizing valuable new drug leads is identification of their protein targets; this is often a time consuming and difficult task. This report is intended to provide a comprehensive review of recent developments in genetic and genomic approaches to overcome the hurdle of discovering the protein targets of bioactive small molecules.