In situ solvent formation microextraction combined with magnetic dispersive micro‐solid‐phase extraction for the determination of benzoylurea insecticides in water samples

A simple, fast, effective, and environmentally friendly method, in situ solvent formation microextraction combined with magnetic dispersive micro‐solid‐phase extraction for the determination of four benzoylurea insecticides is presented herein for the first time. In the proposed method, 1‐hexyl‐3‐methylimidazolium bis[(trifluoromethane)sulfonyl]imide was formed by the reaction between 1‐hexyl‐3‐methylimidazolium chloride and lithium bis[(trifluoromethane)sulfonyl]imide and was used to extract benzoylurea insecticides. Then magnetic nanoparticles were added as carrier to retrieve and separate the ionic liquid from the sample solution. After the supernatant was removed, the ionic liquid was desorbed using acetonitrile and subsequently injected directly into a high‐performance liquid chromatograph equipped with a variable wavelength detector for analysis. The main factors affecting the extraction efficiency were investigated by a one factor at a time approach. Under optimized conditions, the proposed method showed good repeatability (RSD = 2.2–4.5%) and linearity (2–300 μg/L), with correlation coefficients greater than 0.9994 and low limits of detection (0.67–1.46 μg/L). Finally, the method was successfully applied to the analysis of four benzoylurea insecticides in environmental water samples with good recoveries (73.2–85.8%).     

β‐Cyclodextrin polymer@Fe3O4 based magnetic solid‐phase extraction coupled with HPLC for the determination of benzoylurea insecticides from honey,tomato, and environmental water samples

In this work, a magnetic β‐cyclodextrin polymer was successfully prepared and used as an adsorbent for the magnetic solid‐phase extraction of six benzoylurea insecticides (diflubenzuron, triflumuron, hexaflumuron, teflubenzuron, flufenoxuron, and chlorfluazuron) from honey, tomato, and environmental water samples. The influence of the main experimental conditions on the extraction was studied. Under the optimized conditions, the β‐cyclodextrin polymer@Fe₃O₄ showed an excellent extraction performance for the benzoylurea insecticides. A good linearity was obtained for the analytes in the range of 3.0–800 ng/g for honey samples, 0.3–160 ng/g for tomato samples, and 0.1–80.0 ng/mL for water samples, with the correlation coefficients above 0.9998. Satisfactory repeatabilities were achieved, with the relative standard deviations less than 5.7%. The limits of detection (S/N = 3) of the method for the benzoylurea insecticides were 0.2–0.8 ng/g for honey samples, 0.04–0.10 ng/g for tomato samples, and 0.02–0.05 ng /mL for water samples. The method was successfully used for the determination of the six benzoylurea insecticides residues in honey, tomato, and environmental water samples with a satisfactory result.     

Nonwoven polypropylene as a novel extractant phase holder for the determination of insecticides in environmental water samples

In this work, a novel liquid‐phase microextraction approach using nonwoven polypropylene as the extraction solvent holder was developed. Nonwoven polypropylene, a hydrophobic material, is widely used in the cleanup of oil spills. Due to its large surface area, efficient, and full extraction can be achieved. Nonwoven polypropylene containing an ionic liquid was used to extract benzoylurea insecticides (diflubenzuron, teflubenzuron, flufenoxuron, and chlorfluazuron) through vortex‐assisted liquid–liquid microextraction. The parameters that affected the extraction efficiency included the type and volume of the extractant, the extraction time, the time and solvent volume for desorption and the mass and surface area of the nonwoven polypropylene. Under the optimized conditions, good linearity was obtained, with coefficients of determination greater than 0.9996, and the limit of detections of these compounds, calculated at S/N = 3, were in the range of 0.73–5.0 ng/mL. The recoveries of the four insecticides at two spiked levels ranged from 93.3 to 102.0%, with relative standard deviations of less than 4.0%. The proposed method was then successfully used for the rapid determination of benzoylurea insecticides in spiked real water samples before liquid chromatographic analysis. The procedure is simple, inexpensive, easy to execute, and can be widely used.     

Dispersive micro‐solid‐phase extraction of benzoylurea insecticides in honey samples with a β‐cyclodextrin‐modified attapulgite composite as sorbent

A β‐cyclodextrin‐modified attapulgite composite was prepared and used as a dispersive micro‐solid‐phase extraction sorbent for the determination of benzoylurea insecticides in honey samples. Parameters that may influence the extraction efficiency, such as the type and volume of the eluent, the amount of the sorbent, the extraction time and the ionic strength were investigated and optimized using batch and column procedures. Under optimized conditions, good linearity was obtained for all of the tested compounds, with R² values of at least 0.9834. The limits of detection were determined in the range of 0.2–1.0 μg/L. The recoveries of the four benzoylurea insecticides in vitex honey and acacia honey increased from 15.2 to 81.4% and from 14.2 to 82.0%, respectively. Although the β‐cyclodextrin‐modified attapulgite composite did not show a brilliant adsorption capacity for the selected benzoylurea insecticides, it exhibited a higher adsorption capacity toward relatively hydrophobic compounds, such as chlorfluazuron and hexaflumuron (recoveries in vitex honey samples ranged from 70.0 to 81.4% with a precision of 1.0–3.7%). It seemed that the logP_ow of the benzoylurea insecticides is related to their recoveries. The results confirmed the possibility of using cyclodextrin‐modified palygorskite in the determination of relatively hydrophobic trace pharmaceutical residues.     

蔬菜中苯甲酰脲类药物残留的测定方法研究

建立了一步有机溶剂提取、HPLC分离、紫外检测器检测7种苯甲酰脲类药物(除虫脲、灭幼脲、杀铃脲、氟铃脲、氟苯脲、氟虫脲和氟啶脲)在蔬菜中残留量的方法。考察了不同提取溶剂(乙酸乙酯和乙腈)的提取效率;研究了不同C18固相萃取小柱、活性碳、自制弗罗里硅土柱和GPC对蔬菜样品的净化效果;实验了不同的梯度淋洗程序分离7种药物。通过对黄瓜、大白菜、西红柿和包心菜4种蔬菜的4种添加水平和4次重复性实验,建立了一种以乙腈为提取溶剂和以弗罗里硅土柱为净化柱的高效液相色谱法测定7种苯甲酰脲类药物。该方法线性范围为:0.02~1.5mg/L,7种苯甲酰脲类药物的相关系数均大于0.999,其检出限为0.02~0.05mg/kg(S/N=10);在0.05~1.0mg/kg之间的添加回收率为80%~120%;相对标准偏差小于15%。方法完全符合残留分析的要求。     

Magnetic solid‐phase extraction of benzoylurea insecticides in tea samples with Fe3O4‐hyperbranched polyester magnetic composite as sorbent

In this work, a method for the analysis of benzoylurea insecticides, including hexaflumuron, flufenoxuron, lufenuron and chlorfluazuron, in tea samples by high‐performance liquid chromatography with Fe₃O₄‐hyperbranched polyester nanocomposite as the adsorbent for magnetic solid‐phase extraction was developed. The magnetic nanocomposite was prepared and characterized by infrared spectroscopy, vibrating sample magnetometry, and scanning electron microscopy. The as‐prepared nanocomposite was used as a sorbent for the extraction and preconcentration of pesticide residues in tea samples. The extraction and desorption conditions, including mass ratios of raw materials, amount of sorbent, pH value, extraction time, and desorption time, were investigated. Under the final conditions chosen for the analysis, good linearity was obtained for all the tested compounds, with R² values of at least 0.9979. The limits of detection were determined in the range of 0.15–0.3 μg/L. The recovery obtained from the analysis of tea samples with various spiked concentrations was between 90.7 and 98.4%, with relative standard deviations (n = 4) lower than 4.1%. Furthermore, the present approach was successfully applied to the quantitative determination of residues of benzoylurea insecticides in real samples.     

High-performance liquid chromatographic determination of benzoylurea insecticides residues in grapes and wine using liquid and solid-phase extraction

A method for the determination of the benzoylurea insecticides diflubenzuron, triflumuron, teflubenzuron, lufenuron and flufenoxuron in grapes and wine by HPLC has been developed and validated. Grape samples (50 g) were homogenized and extracted with ethyl acetate-sodium sulfate and further cleaned-up by solid-phase extraction on silica sorbent. Wine samples (10 ml) diluted with water (1:3) were solid-phase extracted on an octadecyl sorbent using methanol as the eluent. The pesticides were separated on a reversed-phase octadecyl narrow-bore column by gradient elution and the residues were determined with a UV diode array detector. The calibration plots were linear over the range 0.05-5 micrograms/ml. Recoveries of benzoylurea pesticides from spiked grapes (0.02-2.0 mg/kg) and wine (0.01-0.2 mg/l) were 85.8-101.6% and 69.1-104.8%, respectively, and the limits of quantification for these insecticides were < 0.01 mg/kg for grapes and < 0.01 mg/l for wine. The method was applied to the determination of flufenoxuron and teflubenzuron residues in grapes from treated fields and in produced wine.     

A comparative study of micellar and microemulsion EKC for the analysis of benzoylurea insecticides and their analogs

An investigation of the basic factors which govern the microemulsion EKC (MEEKC) and MEKC for the separation of four benzoylurea (BU) insecticides and their four analogs was carried out. In MEEKC, the separation of eight BU compounds was optimized by changing the microemulsion composition, such as concentration of SDS, octane, n-butanol, and isopropanol percentages, as well as capillary temperature. Separation optimization was also carried out for MEKC, showing that ACN and a high level of another additive gamma-CD were needed to achieve effective separation of these analytes. Although separation with baseline resolution was achieved by either MEEKC or MEKC methods, the separation selectivity resulting from the proposed MEEKC method was completely different from that of MEKC. In addition, analytical time in MEEKC was longer than that in MEKC, but in view of theoretical plate numbers, detection limits, and reproducibility, both methods were effective for the analysis of BU insecticides and their analogs.     

聚多巴胺涂敷的聚酰胺-胺功能化二氧化硅复合材料用于水样中苯甲酰脲类杀虫剂的分散微固相萃取北大核心CSCD

近年来,由农药残留导致的环境污染问题已引起社会的广泛关注,开发便捷高效的分析方法对农药残留进行检测和监测十分必要。研究设计并成功制备了聚多巴胺涂敷的聚酰胺-胺树状分子功能化的二氧化硅复合材料(SiO-PAMAM-PDA),并采用透射电镜对其进行表征。开发了以此复合材料为吸附剂的分散微固相萃取方法(D-μ-SPE),并结合高效液相色谱对水基质中的4种苯甲酰脲类杀虫剂(BUs)残留进行了富集检测。多巴胺结构中含有丰富的苯环、氨基及羟基,可与目标物形成氢键、π-π相互作用,从而增强了材料对苯甲酰脲的萃取能力。对吸附剂用量、萃取时间等可能影响萃取效率的条件进行了单因素优化。在最优条件下,该方法的线性范围在10~500μg/L之间,根据3倍信噪比(S/N)计算所得的检出限(LOD)为1.1~2.1μg/L,回收率为82.8%~94.1%,相对标准偏差(RSD)为2.1%~8.0%。将建立的方法与已报道的以苯甲酰脲作为目标物的方法进行了对比,发现方法样品用量及萃取剂用量均较少,且所需前处理时间较短,有机溶剂消耗也较少,为苯甲酰脲类农药的检测提供了更快速、绿色的选择。为评估所开发方法的实际样品适用性,将其应用于3种河水样品中4种苯甲酰脲类杀虫剂的分析检测,所得回收率及RSD分别为69.5%~99.4%和0.2%~9.5%,表明此方法在实际样品中同样具有较高的准确性和精密度。     

Determination of diflubenzuron and chlorbenzuron in fruits by combining acetonitrile‐based extraction with dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography

In this study, a simple and low‐organic‐solvent‐consuming method combining an acetonitrile‐partitioning extraction procedure followed by “quick, easy, cheap, effective, rugged and safe” cleanup with ionic‐liquid‐based dispersive liquid–liquid microextraction and high‐performance liquid chromatography with diode array detection was developed for the determination of diflubenzuron and chlorbenzuron in grapes and pears. Ionic‐liquid‐based dispersive liquid–liquid microextraction was performed using the ionic liquid 1‐hexyl‐3‐methylimidazolium hexafluorophosphate as the extractive solvent and acetonitrile extract as the dispersive solvent. The main factors influencing the efficiency of the dispersive liquid–liquid microextraction were evaluated, including the extractive solvent type and volume and the dispersive solvent volume. The validation parameters indicated the suitability of the method for routine analyses of benzoylurea insecticides in a large number of samples. The relative recoveries at three spiked levels ranged between 98.6 and 109.3% with relative standard deviations of less than 5.2%. The limit of detection was 0.005 mg/kg for the two insecticides. The proposed method was successfully used for the rapid determination of diflubenzuron and chlorbenzuron residues in real fruit samples.     

Sensitive monitoring of benzoylurea insecticides in water and juice samples treated with multiple monolithic fiber solid-phase microextraction and liquid chromatographic analysis

In present study, a convenient, sensitive and environmentally friendly method for the determination of five benzoylurea insecticides (BUs) in water and juice samples was developed. To extract trace benzoylurea insecticides effectively, poly(methacrylic acid-co-ethylene dimethacrylate) monolith was prepared and used as the sorbent of multiple monolithic fiber solid-phase microextraction (MMF-SPME). The influences of preparation conditions of monolith and extraction parameters of MMF-SPME on BUs were studied thoroughly. Under the optimized conditions, the combination of MMF-SPME with high performance liquid chromatography-diode array detection (MMF-SPME-HPLC-DAD) showed expected analytical performance for target analytes. The limits of detection (S/N = 3) of the developed method were 0.026–0.075 μg L⁻¹ in water and 0.053–0.29 μg L⁻¹ in juice samples. Good linearity was obtained for analytes with the correlation coefficients (R²) above 0.99. Satisfactory repeatability and reproducibility was achieved, with relative standard deviations (RSD) of both less than 10%. Finally, the established MMF-SPME-HPLC-DAD method was successfully applied for the determination of BUs residues in juice and environmental water samples. Recoveries obtained for the determination of BUs in spiking samples ranged from 65.1% to 118%, with RSD below 10% in all cases.     

Pipette vial dispersive liquid–liquid microextraction combined with high‐performance liquid chromatography for the determination of benzoylurea insecticide in fruit juice

A simple, sensitive, and efficient method of using a pipette vial to perform dispersive liquid–liquid microextraction based on the solidification of floating organic droplets was coupled with high‐performance liquid chromatography (HPLC) and a diode array detector for the preconcentration and analysis of four benzoylurea insecticides in fruit juice. In this method, 1‐dodecanol was used as an extractant, and a snipped pipette was used as an experimental vial to simplify the procedure of collecting and separating solidified extractant. The experimental parameters were optimized using a Plackett–Burman design and one‐factor‐at‐a‐time method. Under the optimal conditions in the water model, the limits of detection for analytes varied from 0.03 to 0.28 μg/L, and the enrichment factors ranged from 147 to 206. Linearity was achieved for diflubenzuron and flufenoxuron in a range of 0.5–500 μg/L, for hexaflumuron in a range of 1–500 μg/L, and for triflumuron in a range of 5–500 μg/L. The correlation coefficients for the analytes ranged from 0.9986 to 0.9994 with recoveries of 91.4–110.9%. Finally, the developed technique was successfully applied to fruit juice samples with acceptable results. The relative standard deviations of the analytes at two spiking levels (50 and 200 μg/L) varied between 0.2 and 4.5%.     

Photochemical-spectrofluorimetric method for the determination of benzoylurea insecticides: applications in river water samples and in technical formulations

Ultraviolet (UV) irradiation was used to obtain fluorescent photoproducts from four non-fluorescent benzoylurea (BU) insecticides (flufenoxuron (FLF), lufenuron (LUF), hexaflumuron (HF) and triflumuron (TRF)). The effect of solvent, pH (in aqueous solutions), organic solvent percentage and UV irradiation time on the excitation and emission wavelengths and fluorescence intensity were investigated. The largest fluorescence signals and the shortest UV irradiation time were obtained in methanol, ethanol and 2-propanol. Linear calibration graphs were established in the interval between 0.025 and 1.000 microg ml(-1) from FLF and TRF and between 0.050 and 1.000 microg ml(-1) from LUF and HF with regression coefficients larger than 0.99. A method based on the use of the first-derivative of the spectra of photoproducts was applied to the determination of BU insecticides in river water samples and in technical formulations. The mean recoveries ranged from 95.0% to 110.0% in river water samples and from 92.0% to 101.0% in technical formulations, according to the compound. A preconcentration step, using LLE, allowed to reach the concentration levels established by the EU directive for pesticides in drinking water.     

Nanoporous carbon derived from a metal organic framework as a new kind of adsorbent for dispersive solid phase extraction of benzoylurea insecticides

We describe the preparation of nanoporous carbon using a metal-organic framework (MOF) as a template and furfuryl alcohol as the source for carbon. The MOF consists of a zeolitic framework (ZIF-8) that was obtained from 2-methylimidazole and Zn(II) ions. ZIF-8 was soaked with furfuryl alcohol which then was carbonized at 900 °C. The resulting nanoporous carbon (MOF-C) exhibits a high specific surface area and a large pore volume. It was used as a dispersive solid-phase adsorbent for the preconcentration of the benzoylurea insecticides diflubenzuron, triflumuron, hexaflumuron and teflubenzuron from water and tangerine samples. Under optimized conditions, the methods exhibits excellent extraction performance. The insecticides can be quantified via HPLC with UV detection in the 0.5 to 100 ng mL⁻¹ concentration range in case of spiked tap water, and in the 2.0 to 200 ng g⁻¹ concentration range in case of tangerines. The limits of detection range from 0.10 to 0.23 ng mL⁻¹ in case of water samples, and from 0.34 to 0.71 ng g⁻¹ for tangerine sample (at an S/N ratio of 3). Mean recoveries range from 91.7 to 107.9 %, with relative standard deviations of <7.1 %. The results indicate that the method was efficient for the preconcentration of trace levels of benzoylurea insecticides from water and tangerine samples. Conceivably, this new adsorbent has a large potential with respect to the enrichment of other organic pollutants from various kinds of samples.

Nanoporous carbon was prepared using metal-organic framework (zeolitic imidazolate framework, ZIF-8) as template with furfuryl alcohol as carbon precursor, and was used as dispersive solid phase extraction adsorbent for the enrichment of some benzoylurea insecticides from water and tangerine samples.

     

Poly(vinylidene fluoride) membrane based thin film microextraction for enrichment of benzoylurea insecticides from water samples followed by their determination with HPLC

Thin-film microextraction(TFME),a new geometry for solid-phase microextraction,has become an attractive sample-preparation technique.Compared to other microextraction approaches,the sensitivity of this technique was enhanced without sacrificing the sampling time due to the high surface area-tovolume ratio together with the increase of extraction-phase volume.In this paper,a new TFME method based on poly(vinylidene fluoride) membrane was developed for the extraction of benzoylurea insecticides(diflubenzuron,triflumuron,hexaflumuron and teflubenzuron) from water samples followed by their determination with high performance liquid chromatography-diode array detection.Under the optimal conditions,good linearity was observed over the concentration range of 0.5-100.0 ng/mL with correlation coefficient greater than 0.9994.The limits of detection(S/N = 3) of the method for the target analytes were 0.1 ng/mL.Mean recoveries ranged from 87.7% to 103.9% with relative standard deviations lower than 6.5%.The results indicated that the developed TFME method is simple,efficient,and cost effective.     

Dispersive solid‐phase extraction followed by vortex‐assisted dispersive liquid–liquid microextraction based on the solidification of a floating organic droplet for the determination of benzoylurea insecticides in soil and sewage sludge

A novel dispersive solid‐phase extraction combined with vortex‐assisted dispersive liquid–liquid microextraction based on solidification of floating organic droplet was developed for the determination of eight benzoylurea insecticides in soil and sewage sludge samples before high‐performance liquid chromatography with ultraviolet detection. The analytes were first extracted from the soil and sludge samples into acetone under optimized pretreatment conditions. Clean‐up of the extract was conducted by dispersive solid‐phase extraction using activated carbon as the sorbent. The vortex‐assisted dispersive liquid–liquid microextraction based on solidification of floating organic droplet procedure was performed by using 1‐undecanol with lower density than water as the extraction solvent, and the acetone contained in the solution also acted as dispersive solvent. Under the optimum conditions, the linearity of the method was in the range 2–500 ng/g with correlation coefficients (r) of 0.9993–0.9999. The limits of detection were in the range of 0.08–0.56 ng/g. The relative standard deviations varied from 2.16 to 6.26% (n = 5). The enrichment factors ranged from 104 to 118. The extraction recoveries ranged from 81.05 to 97.82% for all of the analytes. The good performance has demonstrated that the proposed methodology has a strong potential for application in the multiresidue analysis of complex matrices.     

Titanium dioxide nanotubes for solid phase extraction of benzoylurea insecticides in environmental water samples, and determination by high performance liquid chromatography with UV detection

A new, simple and sensitive method was established for solid-phase extraction of benzoylurea insecticides including diflubenzuron, chlorbenzuron, triflumuron, flufenoxuron, and chlorfluazuron in water samples using TiO₂ nanotubes cartridge prior to their determination by liquid chromatography. The parameters influencing the extraction were investigated and optimized. Under optimal conditions, a good linearity was found between the concentration and the peak area in the range from 0.2 to 40???g?L^-1 (r²?>?0.99), and detection limits were in the range from 0.062 to 0.21???g?L^-1. Real water samples were used for validating the method and recoveries of spiked samples were over the range from 82.0 to 100%. The results indicated that TiO₂ nanotubes repesented an attractive alternative sorbent for the enrichment and trace analysis of such pollutants.

硼亲和吸附剂的制备及其对苯甲酰脲类农药的萃取性能

以3-丙烯酰胺苯硼酸（APB）为单体,二乙烯基苯（DVB）为交联剂,“原位”聚合制备了聚（3-丙烯酰胺苯硼酸-二乙烯基苯）多孔硼亲和整体材料并作为搅拌饼固相萃取（SCSE-APBDVB）的萃取介质。以5种苯甲酰脲农药为目标化合物,详细考察了萃取过程中解吸溶剂、样品基底中pH值以及离子强度、萃取和解吸时间等实验条件对萃取效率的影响。在此基础上,与高效液相色谱-二极管阵列检测器联用建立了环境水样和果汁样品中苯甲酰脲农药残留的测定方法。在最佳条件下,在水样和果汁样品中,5种目标化合物的检出限（LOD,S/N=3）分别在0.055~0.11 μg/L和0.095~0.31 μg/L之间,所建立的方法具有理想的日内和日间重现性（RSD值均小于9.0%）。在对实际环境水样和果汁样品的测定中,不同加标浓度苯甲酰脲的回收率为75.6%~109%。研究表明,由于所制备吸附剂与目标化合物存在B-N配位作用、氢键和疏水等多种作用力,因此SCSE-APBDVB可对苯甲酰脲农药进行有效萃取,所建立的分析方法具有简便、灵敏和环境友好等特点。     

Determination of photoirradiated high polar benzoylureas in tomato by HPLC with luminol chemiluminescence detection

This study reports the first analytical application of luminol chemiluminescence reaction for the sensitive detection of two benzoylurea insecticides (diflubenzuron and triflumuron). Off-line experiments demonstrated that previously irradiated traces of these benzoylurea insecticides largely enhanced the chemiluminescence emission yielded from the oxidation of luminol in methanol:water mixtures, by potassium permanganate in alkaline medium, the enhancement being proportional to the concentration of both pesticides. The two benzoylureas were determined in tomato samples by coupling liquid chromatography with post-column photoderivatization and detection based on this chemiluminescence reaction. Tomato samples were extracted using the QuEChERS method based on extraction with acetonitrile and dispersive solid-phase clean-up using primary and secondary amine (PSA). Interferences due to matrix effect were overcome by using matrix-matched standards. The optimised method was validated with respect to linearity, limits of detection and quantification, precision and accuracy. Under the optimised conditions, calibrations graphs were linear between 0.05 and 0.50 μg mL⁻¹ for diflubenzuron and between 0.10 and 1.00 μg mL⁻¹ for triflumuron. Method detection limits were 0.0025 and 0.0131 μg mL⁻¹ (equivalent to 0.0005 and 0.0026 mg kg⁻¹) and quantification limits were 0.05 and 0.10 μg mL⁻¹ (equivalent to 0.01 and 0.02 mg kg⁻¹) for diflubenzuron and triflumuron, respectively. In both cases, quantification limits were lower than the maximum residue levels (MRLs) established by the European legislation. The relative standard deviation of intra-day precision was below 10% and recoveries were between 79.7% and 94.2% for both pesticides.     

Fragmentation study and analysis of benzoylurea insecticides and their analogs by liquid chromatography-electrospray ionization-mass spectrometry

Two insecticides, diflubenzuron and hexaflumuron, and their analogs have been separated by liquid chromatography (LC) and their fragmentation mechanisms were studied by electrospray ionization-ion trap mass spectrometry (ESI-MSⁿ) in both positive- and negative-ion modes. Sequential product ion fragmentation experiments were performed in order to explain the degradation pathways and identify their predominant fragment ions. It was indicated that the characteristic fragmentations are the loss of neutral molecules such as HF, HNO₂, and HCl to form stable ring structure or the cleavage of the acyl amine to form conjugated structure. Furthermore, the separation and determination of two benzoylurea (BU) insecticides and their analogs in the water samples from Weiming Lake have been described by LC-ESI-MS in negative mode. By the use of deprotonated molecule for quantitative analysis at low capillary exit voltage, low detection limits, good linearity and reproducibility for standard solutions were presented.