Sensitive trace enrichment of environmental andiandrogen vinclozolin from natural waters and sediment samples using hollow-fiber liquid-phase microextraction

The presence of vinclozolin in the environment as far as the endocrine disruption effects in biota are concerned has raised interest in the environmental fate of this compound. In this respect, the present study attempts to investigate the feasibility of applying a novel quantitative method, liquid-phase microextraction (LPME), so as to determine this environmental andiandrogen in environmental samples such as water and sediment samples. The technique involved the use of a small amount (3 microL) of organic solvent impregnated in a hollow fiber membrane, which was attached to the needle of a conventional GC syringe. The extracted samples were analyzed by gas chromatography coupled with electron-capture detection. Experimental LPME conditions such as extraction solvent, stirring rate, content of NaCl and pH were tested. Once LPME was optimized, the performance of the proposed technique was evaluated for the determination of vinclozolin in different types of natural water samples. The recovery of spiked water samples was from 80 to 99%. The procedure was adequate for quantification of vinclozolin in waters at levels of 0.010 to 50 microg/L (r> 0.994) with a detection limit of 0.001 microg/L (S/N= 3). Natural sediment samples from the Aliakmonas River area (Macedonia, Greece) spiked with the target andiandrogen compound were liquid-liquid extracted and analyzed by the methodology developed in this work. No significant interferences from the samples matrix were noticed, indicating that the reported methodology is an innovative tactic for sample preparation in sediment analysis, with a considerable improvement in the achieved detection limits. The results demonstrated that apart from analyte enrichment, the proposed LPME procedure also serves as clean-up method and could be successfully performed to determine trace amounts of vinclozolin in water and sediment samples.     

Gas chromatographic determination of 2-hydroxy-4-methoxybenzophenone and octyldimethyl-p-aminobenzoic acid sunscreen agents in swimming pool and bathing waters by solid-phase microextraction

A method has been developed for the trace determination of two sunscreen constituents (2-hydroxy-4-methoxybenzophenone and octyldimethyl-p-aminobenzoic acid) in water samples, which are commonly used in commercial formulations. The method employs solid-phase microextraction (SPME) and gas chromatography with flame ionization and mass spectrometric detection. The technique was developed with headspace and direct sampling in order to demonstrate the applicability of these SPME extraction modes for the identification of these two UV absorbing compounds in waters. The main parameters affecting the SPME process, such as desorption time, extraction time profile, salt additives, pH, and temperature, were investigated. The poly(dimethylsiloxane) 100-microm and polyacrylate 85-microm fiber coatings were found to be the most efficient for the extraction of these compounds from aqueous matrices. Linear calibration curves in the wide range of 10-500 microg/l were obtained for both compounds yielding typical RSD values of 5-9% for both extraction modes. The recoveries were relatively high, 82-98%, with quantitation limits below 1 microg/l. A comparison between the proposed methods and the conventional multiresidue solid-phase extraction revealed that the proposed technique(s) can be reliably used for sunscreen residue measurement in water samples with satisfactory results.     

膜流动电位测试中Ag-AgCl电极的制备及稳定性研究

膜的动电特性研究中,往往采用流动电位方法。该方法中,Ag-Ag Cl测试电极的质量是影响测试准确性的关键要素。本文采用正交试验设计和方差分析,着重考察电解法制备Ag-Ag Cl电极过程中,电流强度(I)、氯化时间(t)、电解质溶液浓度(CHCl)、电极来源(n)、烘烤温度(T)、活化电极溶液浓度(CKCl)等因素对Ag-Ag Cl电极稳定性的影响。得到Ag-Ag Cl电极的最优制备参数为:电流密度3.0m A/cm2,氯化时间50min,盐酸浓度0.1mol·L-1,烘烤温度120℃,活化电极溶液(KCl)浓度0.001mol·L-1;最显著影响因素为电极来源,显著影响因素为氯化时间和烘烤温度。对最优条件组合下制备的AgAg Cl电极,进行了稳定性实验,结果表明:制备的电极具有较好的稳定性,24h内电极电位漂移量小于0.10mv,7天内电极电位漂移量小于0.2mv;在聚偏氟乙烯中空纤维超滤膜流动电位测试中,流动电位与流动压差具有良好的线性和可重复性,回归曲线R20.99,变化规律符合Helmholtz-Smoluehowski公式,可以较好满足膜的流动电位测试要求。     

Determination of Herbicides in Natural Waters Using Solid Phase Microextraction (SPME) and Gas Chromatography Coupled with Flame Thermionic and Mass Spectrometric Detection

Abstract

This study develops a method for solid phase microextraction (SPME) of ten widespread herbicides from water. The selected herbicides belong to different chemical groups are EPTC, molinate, propachlor, trifluralin, atrazine, propazine, terbuthylazine, prometryne, alachlor. Their determination was carried out by gas chromatography with flame thermionic and mass spectrometric detection. To perform the SPME, two types of fibre have been assayed: Carbowax-divinylbenzene (CW-DVB) of 65 μm thickness and polydimethylsiloxane-divinylbenzene (PDMS-DVB) of 65 μm thickness. The main factors affecting the SPME process such as pH, ionic strength, methanol content, memory effect, stirring rate and adsorption-time profile were studied. The method was applied to spiked natural waters such as ground water, sea water, lake water and river water in a concentration range of 0.1 to 10 μg/L. Limits of detection with each of the detectors were determined to be 1 – 20 ng/L in PDMS-DVB and 2–20 ng/L CW-DVB fibres. The recoveries of herbicides compared to distilled water were in relatively high levels 78.3–127.3 % and the average r² values of the calibration curves were above 0.99 for all the analytes. The SPME conditions were finally optimized in order to obtain maximum sensitivity and samples were applied for the trace-level determination in river water samples originating from Ioannina region (Greece).     

A New Organophosphorus Insecticides Removal Process Using Fly ASH

Abstract

Fly ash and soil mixtures with a range of fly ash content from 1 to 100% were used to study adsorption and desorption of four organophosphorus insecticides, ethyl parathion, methyl parathion, fenitrothion and fenthion, in batch experiments. The object of the study was to develop a treatment process using fly ash as sorbent material to isolate/immobilize organic contaminants from aqueous solutions. The adsorption isotherms fit the Freundlich equation x/m=K_dC^1/n. The K_d values increase with the increase of the fly ash content. The isotherms seem to fit the S type, in mixtures of soil with a fly ash content from 0 to 10%, which implies that adsorption becomes easier as the concentration in the liquid phase increases. In mixtures of soil with a fly ash content from 25 to 50% the isotherms become L type and correspond to a decrease of site availability as the solution concentration increases. Finally in mixtures of soil with a fly ash content over 50%, C type adsorption was observed which correspond to a constant partition of the insecticides between the bulk solution and the adsorbent. Mass balance estimations show that the mean percent amounts of insecticides for a range of concentration 0.5–15 mg/l, removed by adsorption in the soil sample are 81.56 % for ethyl parathion, 48.97 % for methyl parathion, 67.06 % for fenitrothion and 86.65 % for fenthion. The adsorption increases as the fly ash content increased and reach the 100% in the “pure” fly ash. The adsorbed amounts of insecticides in mixtures of soils with >50% fly ash content, are up to 99%. In contrast, the amounts of desorption in water decrease as the fly ash content increase.

The results of this research demonstrate that the fly ash shows a significant capacity for adsorption of organophosphorus compounds from aqueous solution and can be used for pesticide removal process.     

Light-induced specular-reflectivity suppression at a gallium/silica interface

The reflectivity of a gallium/silica interface formed on an optical flat or at the tip of a cleaved optical fiber can be reduced in a reversible fashion when the interface is excited by a few milliwatts of laser power. This phenomenon occurs at temperatures just below gallium's melting point. We believe that the effect can be attributed to light-induced structuring at the interface.     

4-氨基-7-硝基苯并-2-氧杂-1,3-二唑类衍生物的合成及其对汞离子的识别研究

以4-氯-7-硝基苯并-2-氧杂-1,3-二唑、乙二胺和溴乙酸乙酯等为原料,合成4-氨基-7-硝基苯并-2-氧杂-1,3-二唑类衍生物(NBD-OEt),通过IR、NMR和MS对其进行结构表征。研究NBD-OEt的吸收光谱和荧光光谱性质,探讨其在H2O/EtOH(60/40, V/V) pH 7.40的HEPES缓冲体系中对Hg₂ 的响应,以及NBD-OEt与Hg₂ 的结合模式。结果表明, 随Hg₂ 的不断加入可诱使NBD-OEt在476nm的吸收峰红移至514nm,并有两个等吸收点(347nm、482nm);其荧光发射峰由536nm红移至559nm,且在525nm出现等发射点;通过Job plot法测定NBD-OEt与Hg₂ 以1:1的计量比结合。     

Analysis of ultrasonic guided waves propagating in long bones and cortical thickness based on time-frequency methods

The ultrasonic signals in long bones contain multiple guided modes which are mutual superposed.The velocities of guided waves in long bones are very sensitive to cortical thickness (CTh).In this paper,Hilbert-Huang transform(HHT) was proposed to analyze multi-mode guided waves,which can decompose superposed waves into many independent modes.Then the group velocity of each mode was obtained at corresponding frequency,which was compared with the results of short time Fourier transform(STFT).The CTh was also obtained by comparing with the theoretical calculation.The results showed that the experimental determined thickness was in agreement with the actual CTh,indicating that measuring the velocity of the guided mode can be used to estimate the CTh.The HHT is an effective method to identify multimode guided waves.