Improved extraction and clean-up of imidazolinone herbicides from soil solutions using different solid-phase sorbents

Extraction and quantification of herbicide residues from soil are important in understanding the behaviour of persistent herbicides. This research investigated extraction and clean-up methods for imidazolinone herbicides from soil and soil amended with organic material. A series of solvent mixes, pH conditions and sorbents was tested. Across three imidazolinone herbicides: imazapyr, imazethapyr and imazaquin, 0.5 M NaOH extraction gave greater than 90% recovery from soil samples; however, 0.5 M NaOH:MeOH (80:20) resulted in higher recovery for imazaquin, but not for the other two herbicides. Of the sorbents tested, the use of chromatographic mode sequencing using C₁₈ and SCX sorbents provided consistent high (>85%) recovery of all three herbicides from soil and separation of the herbicides from other soil components by high performance liquid chromatography (HPLC). These two methods will allow high recovery of these imidazolinone herbicides from soil and have the ability to detect these herbicides without interference from other soil components.     

Separation characteristics of some phenoxy herbicides from aqueous solution

The adsorption and desorption characteristics of some phenoxy herbicides (CPA 2,4-D, and MCPA) from an aqueous solution on the active carbon materials (GAC, F-400) were studied. Adsorption equilibrium capacities of the phenoxy herbicides increased with a decrease in pH of the solution. Adsorption equilibrium isotherms were represented by the Sips equation. Kinetic parameters were measured in a batch adsorber to analyze the adsorption rates of the phenoxy herbicides. The internal diffusion coefficients were determined by comparing the experimental concentration curves with those predicted from the surface diffusion model and the pore diffusion model. The adsorption model based on the linear driving force approximation (LDFA) was used to simulate the adsorption behavior of the phenoxy herbicides in a fixed bed adsorber. Over 95 percent desorption of the phenoxy herbicides was obtained using distilled water.     

Evidence for thermal decomposition contributions to the mass spectra of chlorinated phenoxyacid herbicides obtained by particle beam liquid chromatography mass spectrometry

The spectral quality of a group of chlorinated phenoxyacid herbicides has been shown to degrade under certain conditions upon introduction into the mass spectrometer by a particle beam interface. Experiments were performed to investigate these changes in spectra. Normalized ion chromatograms were generated for the herbicides, and the results showed a broadening of the profiles of some ions, indicating a longer residence time in the ion source. These ions were postulated as coming from the ionization of thermal degradation products from the herbicides. The generation of these ions was dependent on ion source temperature, analyte concentration, and, by implication, ion source cleanliness. Tandem mass spectrometry experiments were performed on these ions from the herbicides and ions from the corresonding phenols. The tandem mass spectra of the ions from the herbicides were similar to the tandem mass spectra of the ions from the phenols. Therefore, it appears that the particle beam mass spectra of the chlorinated phenoxyacid herbicides are composite spectra with contributions from the gas phase ionization of the parent herbidides and thermal decomposition products.     

Screening method for phenoxy acid herbicides in ground water by high-performance liquid chromatography of 9-anthryldiazomethane derivatives and fluorescence detection

A high-performance liquid chromatographic (HPLC) method for phenoxy acid herbicides using precolumn derivatization with 9-anthryldiazomethane (ADAM) is presented. The phenoxy acid herbicides investigated were (2,4-dichlorophenoxy)acetic acid, (4-chloro-2-methylphenoxy)acetic acid, 2-(4-chloro-2-methylphenoxy)propionic acid and (4-chloro-2-methylphenoxy)butyric acid. These herbicides reacted with ADAM under mild conditions and were converted into the corresponding fluorescent derivatives. The ADAM derivatives were separated by reversed-phase HPLC and determined using a fluorescence detector. The detection limits were about 500 pg per injection. For the application of ADAM to the determination of these herbicides in ground waters, the recoveries were more than 93% and the average relative standard deviation was 6.0% at 0.5 microgram/l. The procedure is useful as a screening method for phenoxy acid herbicides in ground water samples.     

Determination of triazine herbicides in foods with liquid chromatography mass spectrometry

Eight residual triazine herbicides and three metribuzin metabolites in foods were determined by liquid chromatography mass spectrometry (LC-MS) with an atmospheric pressure chemical ionization (APCI) interface, under both positive and negative ion modes. Herbicides were extracted with acetonitrile, and no cleanup procedure was adopted in this method. Four foods were spiked with eight herbicides and three metabolites at 0.05 ppm. The average recoveries of these herbicides usually ranged from 82 to 99% and the relative standard deviations were usually around 10%. These results suggest that LC-MS with APCI can be used to determine residues of triazine herbicides in foods.     

苯基脲类除草剂分子印迹聚合物的合成和识别性能研究

以N-(4-异丙基苯基)-N′-亚丁基脲为模板, 甲基丙烯酸为功能单体, 乙二醇二甲基丙烯酸酯为交联剂制备了分子印迹聚合物(MIP). 研究了MIP对苯基脲类除草剂的亲和性和选择性. 在二氯甲烷流动相中制备的MIP对异丙隆(IP)、 非草隆(FN)、 甲氧隆(MX)、 敌草隆(DU)、 绿麦隆(CT)、 枯莠隆(DF)、 灭草隆(MN)、 草不隆(NB)、 播土隆(BT)和伏草隆(FU)等除草剂呈现出较高的亲和性, 而非印迹聚合物(NIP)对文中所用的14种苯基脲类除草剂均表现出非常低的保留或几乎没有保留. 实验及Mulliken电荷计算的结果显示, 苯基脲除草剂分子中的N′原子是主要的识别位点.     

On-line coupled supercritical fluid extraction and chromatography for the determination of thiolcarbamate herbicides in soil matrix

Supercritical fluid extraction (SFE) was on-line coupled with supercritical fluid chromatography (SFC) for the determination of thiolcarbamate herbicides in soil matrix. Inert ODS-silica gel packings were used as a trap column for an interface between SFE and SFC and as an analytical column for the satisfactory separation of extracts. Thiolcarbamate herbicides could be extracted satisfactorily from the soil matrix, which had different characteristics. The results indicated that the proposed system was useful for the rapid determination of thiolcarbamate herbicides in soil matrices.     

Evaluation of surface- and ground-water pollution due to herbicides in agricultural areas of Zamora and Salamanca (Spain)

The pollution of agricultural land due to herbicides was assessed in the Guare?a and Almar river basins, situated in the provinces of Zamora and Salamanca (Spain). A set of fifteen herbicides, including triazines, ureas, amides and others, was selected owing to their frequency of use, the amounts used, their toxicity and their persistence in the environment. Solid-phase extraction with polymeric cartridges, followed by HPLC with diode-array detection, were used to monitor the herbicides. This technique was chosen owing to the wide range of functionality and polarity of the analytes under study. The detection limits obtained were in the 0.004-0.025 microg/l range (lambda=220 nm). Surface and ground waters, taken from different locations in the basins, were analyzed over a 6-month period. The presence of six out of the fifteen herbicides monitored--chlortoluron, atrazine, terbutryn, alachlor, diflufenican and fluazifop-butyl--was detected in several samples at levels ranging from the detection limit to 1.2 microg/l. The relationship of these herbicides to the agricultural activities of the zone is discussed.     

Simultaneous determination of paraquat and diquat in serum using capillary electrophoresis.

The use of capillary electrophoresis for simultaneous separation and detection of the two bipyridylium herbicides, paraquat and diquat, was investigated. Both herbicides were extracted from fortified sera with disposable ODS-silica cartridges. Separation was carried out using a capillary tube (50 microns i.d., 750 mm) of fused silica containing 10 mM glycine-HCl buffer (pH 3.0), 40 mM NaCl and 20% methanol as the carrier. Paraquat and diquat were completely separated in 10 min at an applied potential of 20 kV. On-column UV monitoring allowed detection of both herbicides simultaneously. The assay sensitivity was 0.05 micrograms/mL (signal-to-noise ratio, 2:1), which probably increases with increase in the sample volume of serum. Analytical recovery of both herbicides added to serum was about 97% at concentrations of 0.5-2.0 micrograms/mL.     

Exploiting the Evolutionary Relationship between Malarial Parasites and Plants To Develop New Herbicides

Herbicide resistance is driving a need to develop new herbicides. The evolutionary relationship between apicomplexan parasites, such as those causing malaria, and plants is close enough that many antimalarial drugs are herbicidal and so represent novel scaffolds for herbicide development. Using a compound library from the Medicines for Malaria Venture, the model plant Arabidopsis thaliana, and a physicochemical database of known herbicides, a compound was discovered that showed post‐emergence herbicidal activity equal to commercial herbicides. Using structure–activity analysis, important points for its potency were found. The compound was also tested and found to be active against common crop weeds. Physiological profiling suggested the compound was a photosystem II inhibitor, representing a new scaffold for herbicide development. Overall this approach demonstrates the viability of using antimalarial compounds as lead compounds for the development of much needed new herbicides.     

Behaviour of Phenoxyacetic Acids During Underground Passage with Different Redox Zones

Abstract

The behaviour of the three phenoxyacetic acid herbicides 2,4-D, 2,4,5-T and MCPA during underground passage and bankfiltration was tested in a model system consisting of laboratory filter columns filled with natural underground materials. Different redox environments were reproduced by operating the filters with natural aerobic and anaerobic groundwater. In the presence of oxygen, biodegradation of the three herbicides started after a lag phase. Under sulfate reducing conditions, no degradation could be observed. To assess the factors that may influence microbial degradation in the anaerobic environment, the concentration of herbicides, the time and the nutrient content were varied, but this did not increase degradation. The maximum retention of the herbicides in the filters was 30%, mainly due to adsorption to the filter material.     

Rapid and sensitive detection of the phenoxy acid herbicides in environmental water samples by magnetic solid‐phase extraction combined with liquid chromatography–tandem mass spectrometry

Phenoxy acid herbicides are widely used herbicides that play an important role in improving the yield and quality of crops. However, some research has shown that this kind of herbicide is poisonous to human and animals. In this study, a rapid and sensitive method was developed for the detection of seven phenoxy acid herbicides in water samples based on magnetic solid‐phase extraction followed by liquid chromatography and tandem mass spectrometry. Magnetic amino‐functionalized multiwalled carbon nanotubes were prepared by mixing bare magnetic Fe₃O₄ nanoparticles with commercial amino‐functionalized multiwalled carbon nanotubes in water. Then the amino‐functionalized multiwalled carbon nanotubes were used to enrich phenoxy acid herbicides from water samples based on hydrophobic and ionic interactions. The effects of experimental variables on the extraction efficiency have been studied in detail. Under the optimized conditions, the method validation was performed. Good linearities for seven phenoxy acid herbicides were obtained with squared regression coefficients ranging from 0.9971 to 0.9989. The limits of detection ranged from 0.01 to 0.02 μg/L. The method recoveries of seven phenoxy acid herbicides spiked at three concentration levels in a blank sample were from 92.3 to 103.2%, with inter‐ and intraday relative standard deviations less than 12.6%.     

分子印迹固相萃取-液相色谱质谱联用对4种磺酰脲类除草剂残留的测定

采用苄嘧磺隆分子印迹固相萃取柱(MISPE)对加标大米中的苄嘧磺隆、甲磺隆、苯磺隆和烟嘧磺隆4种磺酰脲类除草剂进行净化和富集预处理,并采用LC-MS方法进行定量分析.质谱条件为:正离子检测模式(M+H),检测质量范围为m/z 200 ～800 ,毛细管电压3.93 kV,锥孔电压20 V,脱溶剂温度250 ℃,辅助气流速4 L/min.4种磺酰脲类除草剂在0.01 ～0.70 mg·L~(-1)范围内线性良好.回收率为68% ～100%,表明样品液中的烟嘧磺隆、甲磺隆、苯磺隆和苄嘧磺隆能直接被分子印迹固相萃取柱中的印迹位点保留,而杂质几乎不被保留.分子印迹固相萃取柱对磺酰脲类除草剂表现出良好的识别性能.     

Selective high performance liquid chromatography imprinted-stationary phases for the screening of phenylurea herbicides in vegetable samples

Molecularly imprinted polymers (MIPs) for the determination of phenylurea herbicides have been synthesized by polymerisation of the appropriated reagents mixture within the pores of preformed spherical silica particles leading to a silica-MIP composite material. Subsequently, the silica matrix was etched away resulting in MIP beads which can be considered the "mirror image" of the original silica mold. The MIP particles were packed in stainless steal HPLC columns (125mmx4.6mm I.D.) and the materials were evaluated as imprinted-stationary phases for phenylurea herbicides. The imprinting effect of the originated specific binding sites for the selective recognition of phenylurea herbicides was clearly demonstrated. An efficient separation of a mixture of phenylurea herbicides in two groups, with or without a methoxy group in the chemical structure, was achieved and well shaped and defined peaks were obtained. Finally, the optimum imprinted column (prepared using linuron as template, 2-(trifluoromethyl)-acrylic acid as monomer, 72h of polymerisation time and the subsequent dissolution of silica matrix) was used for the LC-UV screening of phenylurea herbicides directly from vegetable sample extracts without any previous clean-up step at low concentration level in less than 10min.     

Enantiomeric and isomeric separation of herbicides using cyclodextrin-modified capillary zone electrophoresis

Cyclodextrin-modified capillary zone electrophoresis (CD-CZE) was applied successfully to the enantiomeric and isomeric separation of three herbicides (imazaquin, diclofop and imazamethabenz). Commercially available cyclodextrins were evaluated for separation of the enantiomers and isomers of the three herbicides having varied molecular structures. The enantiomers of imazaquin and diclofop, and the isomers of imazamethabenz could be resolved with a resolution of ≥1.5. The resolution was found to depend on pH of the run buffer, cyclodextrin type and cyclodextrin concentration. By employing mixed cyclodextrins in the running buffer, the three herbicides were simultaneously separated in a single run. In addition, rapid (less than 3 min) enantiomeric separation is demonstrated using imazaquin as a model herbicide. The reported capillary electrophoresis (CE) methods are simple, rapid, efficient and reproducible and our results demonstrate that CE provides a powerful analytical tool for enantiomeric and isomeric separation of herbicides.     

基于十八烷基三甲基溴化铵修饰的磁性粒子在线磁性固相萃取-高效液相色谱法测定水样中磺酰脲类农药

采用溶胶-凝胶法制备表面修饰了十八烷基三甲基溴化铵的磁性粒子作为萃取剂，研制了一种在线磁性固相萃取（on-line MSPE）装置，建立了on-line MSPE与高效液相色谱联用测定水样中两种磺酰脲类农药（氯磺隆、苄嘧磺隆）的方法。实验优化了在线磁性固相萃取条件并进行方法学考察，证明该方法具有良好的线性关系（两种目标物的线性相关系数均≥ 0.9997）和较低的检出限（两种目标物的检出限分别为0.32和1.12 μg/L）。将此法用于3种环境水样中两种磺酰脲类农药的检测，水样中均检出氯磺隆，均未检出苄嘧磺隆。两种目标物加标回收率为70.0%~113.4%。该方法高效、简便，在分离富集环境水样中磺酰脲类农药方面有一定的应用前景。     

Determination of kinetic and equilibrium regimes in the operation of polar organic chemical integrative samplers. Application to the passive sampling of the polar herbicides in aquatic environments

This work set out the laboratory calibration of the passive samplers such as polar organic chemical integrative samplers (POCISs) which preconcentrate hydrophilic organic contaminants in aqueous medium. We compared the two different configurations available (i.e. pesticide and pharmaceutical POCISs) for sampling different classes of herbicides representative of a wide range of polarity (5.34>of=log Kow>or=-1.70). The results showed that pharmaceutical configuration was probably more convenient for sampling basic, neutral or acidic herbicides. Afterward, we performed a kinetic study with the pharmaceutical POCIS only. This calibration revealed linear and integrative uptakes of several herbicides for 21 days. For some compounds like sulcotrione, mesotrione, deisopropylatrazine (DIA) and deethylatrazine (DEA), the linear uptake model was only valid for 10 days. Lastly, we observed an increase of the sampling rates with the hydrophobicity of the herbicides.     

Switchable hydrophilic solvent-based dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography for the determination of four types of sulfonylurea herbicides in soils

In this study, switchable hydrophilic solvent-based dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography was developed for the determination of four sulfonylurea herbicides in soils. For the first time, the sample pretreatment was achieved due to the similar acid-base status of sulfonylurea herbicides and switchable hydrophilic solvent. In the extraction step, sulfonylurea herbicides were extracted as anions and transferred to an alkaline solution with switchable hydrophilic solvent anions. In the concentration step, two types of anions were transformed to their molecular state after the aqueous solution was acidified. In addition, the dispersion and microextraction processes were completed efficiently with the simultaneous formation of analytes and extractants. The factors affecting the extraction performance were optimized. Under the optimized conditions, good linearity was observed for each herbicide with correlation coefficients ranging from 0.9952 to 0.9978. The limits of detection were in the range of 0.1–0.2 μg/g. Moreover, the relative recoveries of the sulfonylurea herbicides at spiking levels of 0.5, 1, and 1.5 μg/g in soil samples were between 75 and 111% (relative standard deviations: 0.4–11.4%). Therefore, the proposed method in this study could be successfully applied to the analysis of four types of sulfonylurea herbicides in soil samples.     

Synthesis and Biological Activity of N-Dichloroacetyl-3-methyl-2-n-propyl-1-oxa-4-aza-spiro-4,5-decane

Introduction Herbicide safeners are the compounds which can protect crops from being injured by herbicides and enhance the tolerance of crops to herbicides. They can enlarge the application scope of herbicides.     

磺酰脲类除草剂残留检测技术及其研究进展

磺酰脲类除草剂具有高效、低毒、低残留等特点,已经成为当前使用量最大的一类除草剂.随着该类除草剂在农业生产中的广泛使用,其残留问题以及对后茬作物产生的危害已经引起关注.由于磺酰脲类除草剂在环境和生物样品中痕量存在,且其化学和热不稳定,酸性条件下易水解,以及最大残留限量值日益严格,使其残留分析成为一项极具挑战性的工作.该文综述了近年来磺酰脲类除草剂残留分析的前处理方法和检测技术的研究进展,并详细介绍了分子印迹技术、在线联用技术和液相色谱-串联质谱技术在该类除草剂检测中的应用及其前景,为今后分析检测各类样品基质中磺酰脲类除草剂的残留提供参考和依据.