Application of solid-phase extraction and micellar electrokinetic capillary chromatography to the study of hydrolytic and photolytic degradation of phenoxy acid and phenylurea herbicides

A degradation study of two phenoxy acid [(2,4-dichlorophenoxy) propanoic acid and (2,4,5-trichlorophenoxy) acetic acid] and two phenylurea (diuron and monolinuron) herbicides, spiked at 50 ppb in water, was performed. Some samples were subjected to neutral and basic hydrolysis; other samples were subjected to photolysis using either sunlight or a xenon arc lamp. After degradation, the water samples were preconcentrated using solid-phase extraction (SPE) with Carbopack B columns and analysed by a micellar electrokinetic capillary chromatography (MECC) system with UV detection at 210 nm. Phenoxyacetic acids were not degraded neither by hydrolysis nor by sunlight photolysis, but they were photodegraded when they were exposed to a xenon arc lamp, with half-lives around 300 min. Phenylurea herbicides were hydrolysed at the two-tested pH, with half-lives varying from 25 to 290 days. The main hydrolysis products were the corresponding chloroanilines. Diuron and monolinuron were also degraded when they were exposed to sunlight and xenon arc lamp. The main photodegradation pathway for diuron corresponded to dehalogenation, while for monolinuron dealkylation and hydroxylation were also postulated. The toxicity of the studied herbicides and their degradation products was evaluated by means of Microtox tests. The obtained results indicated that the toxicity of the degraded samples was higher than the toxicity of the herbicides.     

Identification of New Photodegradation Byproducts of the Antifouling Agent Irgarol in Seawater Samples

Abstract

A photodegradation study for Irgarol was carried out in order to investigate several products of degradation formed in different environmental matrices and under different conditions. Deionized water, groundwater and seawater samples, spiked at 30–100 μg/L with Irgarol, were irradiated using a xenon are lamp and/or sunlight. Aliquots of the spiked water samples were taken at different times of irradiation and compounds were isolated from the water samples by means of solid-phase extraction (SPE) using either C₁₈ or PLRP-s cartridges. Separation and detection of the compounds was accomplished by several analytical methodologies such as liquid chromatography-diode array detection (LC-DAD), liquid chromatography-electrospray ionization/mass spectrometry (LC-ESI/MS) and gas chromatography-mass spectrometry (GC-MS). Four new byproducts, with molecular weights of 167, 197, 207 and 213, were identified in this photodegradation study. When the photolysis was carried out with xenon lamp, half-lives of Irgarol were 103.8, 125.4 and 107.5 minutes in deionized water, groundwater and seawater, respectively. In seawater samples, a 98% of degradation was observed for Irgarol, after 217 hours of solar irradiation, being the main byproduct formed that corresponding to M_w = 213. On the other hand, the use of two different sensitizers -(TiO₂/H₂O₂), (FeCI₃/H₂O₂)- was also evaluated in deionized water samples containing Irgarol. These experiments were carried out in order to evaluate the use of these two sensitizers for decontamination of polluted waters.     

Identification of photocatalytic degradation products of non-ionic polyethoxylated surfactants in wastewaters by solid-phase extraction followed by liquid chromatography-mass spectrometric detection

The photodegradation of non-ionic surfactants (nonylphenol- and alcohol-polyethoxylates, NPEOx and CnEOx) was investigated in different waters with and without a photoinducter (Fe(III)). Deionized water and industrial effluent spiked at 0.5 mg/L with C10EO6 and NPEO9 were irradiated using a xenon arc lamp. Aliquots of the test solutions were taken at different time intervals and were preconcentrated using solid phase extraction (SPE) with C18 cartridges. Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) was used to identify the chemical species generated from phototransformation of non-ionic surfactants. The intermediates detected included nonylphenol diethoxylate (NPEO2) and nonylphenol ethoxy acetic acid (NPE2C). Much smaller amounts of degradation products of NPEO9 having only the alkyl chain carboxylated were also formed in the photocatalysis experiment. The identified C10EO6 photoproducts included fatty alcohols and acids. Polyethylene glycols (PEGs) were also formed as the consequence of the central scission of C10EO6 and the deethoxylation of NPEO9. The photodegradation in wastewater samples was more efficient than in deionized water being the half-life (t(1/2)) of C10EO6, 48 h and 29 h in deionized water and wastewater, respectively, and for NPEO9, 17 h and 14 h in deionized water and wastewater, respectively. When induced photodegradation was undertaken, the t(1/2) for NPEO9 was 21 min and 29 min in deionized water and wastewater, respectively. Disappearance of parent compounds was observed after 120 h from the beginning of the photodegradation experiment, or after 210 min of irradiation for the photocatalysis.     

Atrazine toxicity reduction following H2O2/TiO2- photocatalyzed reaction and comparison with H2O2- photolytic reaction

An atrazine photodegradation study carried out by a Q-Panel suntest apparatus is reported in this work. H2O2/TiO2 photocatalyzed reaction yield and parameters (time, irradiance, temperature, H2O2 (40%) volume, TiO2 amount) were exactly determined relating to the used atrazine concentration. An experimental kinetic study was performed to establish the reaction order in fixed conditions. Using a biosensor method, 10(-4) M Atrazine solution toxicity and final photocatalytic reaction solution toxicity were quantitatively determined. A consistent toxicity decrease was observed on passing from the analyte to the products of the photocatalytic reaction. An analogous photolytic reaction carried out in absence of TiO2, but in the same experimental conditions of time, irradiance, temperature and H2O2 volume, brings to a toxicity increase.     

Photocatalytic reaction by Fe(III)–citrate complex and its effect on the photodegradation of atrazine in aqueous solution

The photodegradation of atrazine in aqueous solutions containing citrate and Fe(III) was studied under Xe lamp irradiation on a time scale of hours. It was found that the presence of Fe(III)–citrate complex enhanced the photodegradation rate of atrazine as a result of OH attack. Atrazine photodegradation followed first-order reaction kinetics and the rate depended upon pH and light intensity. High citrate concentrations led to increased photodegradation of atrazine due to the fact that citrate not only acted as a carboxylate ligand but also a reductant of Fe(III). The interaction of Fe(III) with citrate was characterized using UV–visible absorption and Fourier-transform infrared (FTIR) spectroscopy, indicating that the hydrogen ions on the carboxyl groups were exchanged for Fe(III) ions. On the basis of these results, a reaction scheme was proposed in which the cycling of iron and carbon, the depletion of citrate and O₂, and the formation of reactive oxygen species (ROS) were involved.     

Oriented antibody immobilization for atrazine determination by a flow-through fluoroimmunosensor

An atrazine flow-through fluoroimmunosensor was developed, based on an oriented antibody covalently bound to Protein-A (Prot-A) immobilized on Controlled Pore Glass (CPG). Atrazine was detected “in-situ” by placing the immobilized antibody in the optical path of the flow cell. Immobilization of 30 μg of polyclonal anti-atrazine antibody on 0.5 g of Prot-A-CPG provided the highest sensitivity. The effect of several solvents on the covalently immobilized antibodies regeneration was evaluated, the optimum conditions being achieved by pumping 5% acetonitrile (pH = 3) at 0.15 mL/min for 100 s. The detection limit of the immunosensor was 0.7 μg/L and the reproducibility was 2% and 4% for 5 μg/L and 40 μg/L, respectively, in the optimum working concentration range (0.7–50 μg/L). This device allowed 12 samples per hour to be analyzed and had a life-time of 200 assays. Simazine and desisopropylatrazine (DIA) were not cross-reactive, desethylatrazine (DEA) has a cross-reactivity of 8% and propazine and prometryn of 44% and 27%, respectively. The immunosensor was applied to the determination of atrazine in tap and ground water samples spiked at the ¶10 and 30 μg/L concentration level.     

Identification of Carbofuran And Methiocarb and their Transformation Products in Estuarine Waters by On-line Solid Phase Extraction Liquid Chromatography—Mass Spectrometry

Abstract

The degradation of the carbamate insecticides carbofuran and methiocarb in distilled and natural waters was determined. Degradation studies were carried out both under a xenon arc irradiation and natural sunlight at pesticide concentrations of 50–100 μg/L. 50–100 mL water sample were preconcentrated using automated online solid phase extraction (SPE) followed by liquid chromatography (LC), UV detection or post column fluorescence detection (EPA method 531.1 for carbamate insecticides). Structure identification was carried out by on-line SPE-LC-MS either with thermospray and/or high flow pneumatically assisted electrospray interfaces. Half-lives varying between 4–12.5 days for carbofuran and methiocarb were determined under natural sunlight exposure, being chemical hydrolysis the major degradation pathway. When using xenon arc lamp irradiation both pesticides degraded very rapidly with half-lives varying from 0.3–1.7 hours. The various degradation products identified were: methiocarb sulfoxide, 4-methylthio-3, 5-dimethylphenol, 3-hydroxy-7-carbofuranphenol and 2-hydroxy-3-(2-methylprop-1-enyl)-phenyl-N-methylcarbamate.     

Liquid chromatography/time-of-flight mass spectrometric analyses for the elucidation of the photodegradation products of triclosan in wastewater samples

Liquid chromatography coupled with time-of-flight mass spectrometry (LC/TOFMS) was applied for the identification of four new photodegradation products of triclosan, a major antimicrobial agent used in personal care products. Wastewater samples, spiked at 7 microg/mL with triclosan, were irradiated with natural sunlight in order to generate the photodegradation products. Aliquots of the spiked water samples were taken at different times of irradiation and compounds were isolated from the water samples by solid-phase extraction. Separation and detection of the compounds and degradation products were accomplished by LC/TOFMS, which provided highly selective information about elemental compositions. Accurate mass measurements for the four degradation products permitted postulation of proposed empirical formulae in this study. Replacement of chlorine atoms by hydroxyl groups and chlorine losses are the major degradation pathways proposed. The degradation products were formed also under environmental conditions in wastewater matrices, thus suggesting their presence in real wastewater treatment processes.     

新型N-TiO2的固相法制备及其光催化性能

以纳米管钛酸为前驱体,以NH4HCO3为N源,先机械研磨使二者混合均匀,再在Ar保护下,于不同温度焙烧4h制得N掺杂TiO2 (N-TiO2),并采用X射线粉末衍射、X射线光电子能谱、紫外-可见吸收光谱、透射电镜及N2吸附-脱附对样品进行了表征.结果显示,N以间隙掺杂方式进入TiO2晶格内.在热处理过程中,生成中间体(...     

Identification of photocatalytic degradation products of non-ionic polyethoxylated surfactants in wastewaters by solid-phase extraction followed by liquid chromatography-mass spectrometric detection

The photodegradation of non-ionic surfactants (nonylphenol- and alcohol-polyethoxylates, NPEO_x and C_nEO_x) was investigated in different waters with and without a photoinducter (Fe(III)). Deionized water and industrial effluent spiked at 0.5 mg/L with C₁₀EO₆ and NPEO₉ were irradiated using a xenon arc lamp. Aliquots of the test solutions were taken at different time intervals and were preconcentrated using solid phase extraction (SPE) with C₁₈ cartridges. Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) was used to identify the chemical species generated from phototransformation of non-ionic surfactants. 2 ) and nonylphenol ethoxy acetic acid (NPE₂C). Much smaller amounts of degradation products of NPEO₉ having only the alkyl chain carboxylated were also formed in the photocatalysis experiment. The identified C₁₀EO₆ photoproducts included fatty alcohols and acids. Polyethylene glycols (PEGs) were also formed as the consequence of the central scission of C₁₀EO₆ and the deethoxylation of NPEO₉. The photodegradation in wastewater samples was more efficient than in deionized water being the half-life (t_1/2) of C₁₀EO₆, 48 h and 29 h in deionized water and wastewater, respectively, and for NPEO₉, 17 h and 14 h in deionized water and wastewater, respectively. When induced photodegradation was undertaken, the t_1/2 for NPEO₉ was 21 min and 29 min in deionized water and wastewater, respectively. Disappearance of parent compounds was observed after 120 h from the beginning of the photodegradation experiment, or after 210 min of irradiation for the photocatalysis. Received: 27 September 2000 / Revised: 11 January 2001 / Accepted: 14 January 2001     

UV/H2O2/草酸铁络合物光降解偶氮蓝染料的研究

光氧化法是近年来日益受人们重视的一种治理染料废水的新方法,而现有方法光量子效率低、光能耗大、处理费用高。已有研究表明草酸铁络合物有较高的光降解效率。而在到达地面的太阳辐射中,紫外辐射只占4％左右,所以研究弱紫外辐射下光降解染料废水意义重要。本文用6W低压汞灯光源,过氧化氢．草酸铁络合物光降解水溶液中的偶氮蓝染料,考察pH值、H2O2浓度、染料浓度及光强等因素对降解结果的影响,探讨以自然光为光源催化降解偶氮蓝染料的可行性。     

Oriented antibody immobilization for atrazine determination by a flow-through fluoroimmunosensor

An atrazine flow-through fluoroimmunosensor was developed, based on an oriented antibody covalently bound to Protein-A (Prot-A) immobilized on Controlled Pore Glass (CPG). Atrazine was detected “in-situ” by placing the immobilized antibody in the optical path of the flow cell. Immobilization of 30 μg of polyclonal anti-atrazine antibody on 0.5 g of Prot-A-CPG provided the highest sensitivity. The effect of several solvents on the covalently immobilized antibodies regeneration was evaluated, the optimum conditions being achieved by pumping 5% acetonitrile (pH = 3) at 0.15 mL/min for 100 s. The detection limit of the immunosensor was 0.7 μg/L and the reproducibility was 2% and 4% for 5 μg/L and 40 μg/L, respectively, in the optimum working concentration range (0.7–50 μg/L). This device allowed 12 samples per hour to be analyzed and had a life-time of 200 assays. Simazine and desisopropylatrazine (DIA) were not cross-reactive, desethylatrazine (DEA) has a cross-reactivity of 8% and propazine and prometryn of 44% and 27%, respectively. The immunosensor was applied to the determination of atrazine in tap and ground water samples spiked at the ?10 and 30 μg/L concentration level. Received: 30 April 1999 / Revised: 16 July 1999 / Accepted: 21 July 1999     

Cr2O3/C@TiO2核壳型复合材料的设计合成及其光催化产氢性能

随着社会经济的快速发展,能源危机和环境污染问题成为世界各国关注的焦点.通过光催化剂将太阳能用于污染物降解、分解水产氢、CO2还原及有机物合成等领域,是解决上述问题的理想途径.过渡金属氧化物TiO2因其稳定性高、催化活性好、制备简单等优点,被认为是最理想的光催化材料.然而,TiO2带隙较宽、光响应范围窄、光量子效率低等缺点限制了其实际应用.将碳或Cr2O3与TiO2结合形成复合结构已被证明可以有效提升其光催化性能.另一方面,金属离子的掺杂可以有效提高氧化钛的可见光响应.本文利用具有高比表面积的金属有机骨架材料MIL-101(Cr)纳米材料作为模板、镉源和碳源,首先在MIL-101(Cr)表面可控生长TiO2纳米颗粒,获得MIL-101(Cr)@TiO2复合结构;然后在氮气保护下碳化形成Cr2O3/C@TiO2核壳型复合材料.碳化后,制备的复合材料具有模板的八面体形貌和高比表面积,MIL-101(Cr)中的Cr元素一部分会形成Cr2O3,一部分会掺杂到TiO2中,使得TiO2的吸收边红移.此外,Cr2O3/C@TiO2中的C有利于光的吸收和载流子的分离.这种独特的纳米结构赋予Cr2O3/C@TiO2复合材料优异的光催化性能.在300 W氙灯照射下,该复合材料光解水产氢的速率为446μmol h?1 g?1,约为纯TiO2的4倍.在可见光照射下,Cr2O3/C@TiO2分解水产氢的速率为25.5μmol h?1 g?1.将获得的粉体催化剂制备成光电极发现,Cr2O3/C@TiO2在全幅光照射下的光电流密度在0.4 V(vs.Ag/AgCl)下达到2.3 mA/cm2,约为纯TiO2的3.5倍.Cr2O3/C@TiO2光催化产氢活性的提高一方面是由于Cr掺杂到TiO2中使得其具有可见光响应,另一方面MIL-101碳化获得的Cr2O3/C有效促进了光生载流子的分离.     

Cr2O3/C@TiO2核壳型复合材料的设计合成及其光催化产氢性能

随着社会经济的快速发展,能源危机和环境污染问题成为世界各国关注的焦点.通过光催化剂将太阳能用于污染物降解、分解水产氢、CO2还原及有机物合成等领域,是解决上述问题的理想途径.过渡金属氧化物TiO2因其稳定性高、催化活性好、制备简单等优点,被认为是最理想的光催化材料.然而,TiO2带隙较宽、光响应范围窄、光量子效率低等缺点限制了其实际应用.将碳或Cr2O3与TiO2结合形成复合结构已被证明可以有效提升其光催化性能.另一方面,金属离子的掺杂可以有效提高氧化钛的可见光响应.本文利用具有高比表面积的金属有机骨架材料MIL-101(Cr)纳米材料作为模板、镉源和碳源,首先在MIL-101(Cr)表面可控生长TiO2纳米颗粒,获得MIL-101(Cr)@TiO2复合结构;然后在氮气保护下碳化形成Cr2O3/C@TiO2核壳型复合材料.碳化后,制备的复合材料具有模板的八面体形貌和高比表面积,MIL-101(Cr)中的Cr元素一部分会形成Cr2O3,一部分会掺杂到TiO2中,使得TiO2的吸收边红移.此外,Cr2O3/C@TiO2中的C有利于光的吸收和载流子的分离.这种独特的纳米结构赋予Cr2O3/C@TiO2复合材料优异的光催化性能.在300 W氙灯照射下,该复合材料光解水产氢的速率为446μmol h?1 g?1,约为纯TiO2的4倍.在可见光照射下,Cr2O3/C@TiO2分解水产氢的速率为25.5μmol h?1 g?1.将获得的粉体催化剂制备成光电极发现,Cr2O3/C@TiO2在全幅光照射下的光电流密度在0.4 V(vs.Ag/AgCl)下达到2.3 mA/cm2,约为纯TiO2的3.5倍.Cr2O3/C@TiO2光催化产氢活性的提高一方面是由于Cr掺杂到TiO2中使得其具有可见光响应,另一方面MIL-101碳化获得的Cr2O3/C有效促进了光生载流子的分离.     

Cu2+/TiO2对甲基橙的光催化降解机理

以自制的掺铜离子的混晶型二氧化钛为光催化剂,考察了甲基橙光催化降解过程中pH值和光源的影响,提出了两种不同的光催化降解机理:在高压汞灯照射下,TiO2的价带电子被激发到导带,光生电子和空穴主要通过Cu2+ 的短路循环而复合,光催化剂的活性降低;在太阳光照射下,甲基橙发生自身光敏化氧化反应,受激电子从单线态或三线态的甲基橙分子跃迁到TiO2的导带,Cu2+起到电荷传递中继站的作用,加速了注入电子向H2O2的转移,从而促进了甲基橙的光催化降解。     

Correlation between hue angle and lightness of light irradiated wood

The objective of this study was to investigate irradiation characteristics of Beech (Fagus crenata Blume), black locust (Robinia pseudoacacia L.), Japanese cedar (Cryptomeria japonica D. Don) and spruce (Picea abies Karst.) wood samples by sunlight, xenon light and mercury vapour light. The colour change of the samples was evaluated by CIE L*a*b* and L*h*c* colour co-ordinate systems. It was found that the samples showed a rapid colour change at the initial period of treatment but the rate of change decreased with treatment time. It was determined that neither xenon nor mercury lamp light can accurately simulate sunlight. A wide range of colour changes were caused by the applied light sources. In spite of this wide colour range a good linear correlation was found between the lightness and the colour hue. The coefficients of determination (R²) are between 0.7 and 0.96. Accordingly, this linear correlation gives the possibility of following the colour change during photodegradation by measuring only the lightness.     

固液萃取-高效液相色谱-串联质谱法同时测定土壤中阿特拉津及其降解产物

建立了高效液相色谱-串联质谱法(HPLC-MS/MS)同时检测土壤中阿特拉津及其降解产物残留的分析方法。样品以甲醇-水(4∶1,V/V)作为提取溶剂,使用涡旋振荡提取,采用HPLC-MS/MS法进行测定,外标法定量。在0.01、0.2和5.0mg/kg三个添加浓度水平下,阿特拉津及其降解产物的平均回收率在73.7%~104.7%之间,相对标准偏差为0.4%~5.1%;阿特拉津,羟基阿特拉津在土壤样品中的方法检出限均0.045μg/kg,而脱乙基阿特拉津、脱乙基脱异丙基阿特拉津及脱异丙基阿特拉津在土壤样品中的方法检出限则分别为0.090、0.45和0.90μg/kg。本方法的灵敏度较高,且简便、快速,能较好的解决目标物极性差别大及样品基质对检测结果的干扰等问题,可以满足土壤中阿特拉津及其降解产物残留检测的需要。     

Photocatalysis effect of nanometer TiO2 and TiO2-coated ceramic plate on Hepatitis B virus

The photocatalysis effect of nanometer TiO2 particles and TiO2-coated ceramic plate on Hepatitis B virus surface antigen (HBsAg) was investigated. The ELISA (enzyme-linked immunosorbent assay) standard method was used to assess the efficiency of TiO2 material to destroy the HBsAg. The research has shown that the suspension of TiO2 (0.5g/L) can destroy most of the HBsAg under the irradiation of mercury lamp, with the light intensity of 0.6mW/cm(2) at 365nm wavelength, or under the sunlight irradiation for a few hours. TiO2-coated ceramic plates can also destroy the HBsAg under the irradiation of mercury lamp, with the light intensity of 0.05mW/cm(2) at 365nm wavelength or under the room daylight for a few hours.     

Atrazine and Parathion-Methyl Removal by UV And UV/O3 in Drinking Water Treatment

Abstract

The degradation of atrazine and parathion-methyl by UV-light in the presence of O₂(UV/O₂) and by a combination of UV-light and ozone in the presence of O₂(UV/O₂/O₃) was studied at a pilot plant for drinking water treatment. The photolysis rate of parathion-methyl increased with UV/O₂/O₃ compared to the treatment with UV/O₂ only, while the photodecomposition rate of atrazine was not enhanced by the UV/O₂/O₃ combination under the working conditions applied.

In field experiments with a large-scale plant the degradation of atrazine and desethylatrazine was studied at a drinking water supply. The applied ozone dose rates were smaller and the residence time of the liquid phase in the UV-reaction unit was shorter than in the pilot plant. The degradation rate of both atrazine and desethylatrazine increased with increasing ozone dose rates and increasing radiant power. At a continuous flow rate of 70 m³/h of contaminated raw water atrazine could be degraded below the threshold limit for pesticides (0.1[ugrave]g/L) at optimum operation conditions, whereas the resulting desethylatrazine concentration exceeded this limit. At a continuous flow rate of 30 m³/h desethylatrazine could be degraded below the threshold limit, too.     

共沉淀法制备稀土Ce掺杂的纳米ZnO及其光催化降解染料的性能

以六水合硝酸锌和六水合硝酸铈?髥为原料,通过共沉淀法制备了一系列稀土Ce掺杂的纳米ZnO,并采用X射线粉末衍射(XRD)、傅里叶红外光谱(IR)、扫描电镜(SEM)、X射线能谱分析(EDS)、紫外可见漫反射光谱对其进行了全面表征。部分样品还通过X射线光电子能谱(XPS)和光致荧光光谱(PL)进行了进一步分析。分别在日光和紫外光条件下,对这一系列Ce掺杂的ZnO进行了光催化降解亚甲基蓝的性能研究,得出当Ce的掺杂量为3%(n/n)时(ZnO-3%Ce),其光催化活性最佳,光催化降解亚甲基蓝的效率均超过98%。选取ZnO-3%Ce作为催化剂,分别进一步考察其在日光和紫外光下对罗丹明B和甲基橙的光催化降解性能。研究结果表明,ZnO-3%Ce在日光和紫外光下均表现出较好的光催化降解效果,体现出良好的光降解普适性。日光下光降解效率顺序为:亚甲基蓝>罗丹明B>甲基橙,而紫外光下降解效率顺序为:罗丹明B>亚甲基蓝>甲基橙。最后,我们研究了催化剂ZnO-3%Ce的循环利用及稳定性性能。实验结果表明:该催化剂循环使用3次之后,光催化效率仍然稳定在97%以上,并且其结构和组成保持不变,体现出优异的稳定性和应用前景。