Multiresidue determination of pyrethroid pesticide residues in pepper through a modified QuEChERS method and gas chromatography with electron capture detection

This study developed and used a modified quick, easy, cheap, efficient, rugged and safe (QuEChERS) method coupled with gas chromatography with electron capture detection to determine eight pyrethroid pesticide residues in green, red and dehydrated red peppers. Pyrethroids were extracted with acetonitrile, partitioned with sodium chloride and purified with primary secondary amino and graphitized carbon black in hexane. The QuEChERS extraction conditions were optimized, and the matrix effects that might influence recoveries were evaluated and minimized using matrix‐matched calibration curves. Under the optimized conditions, the calibration curves for pyrethroid pesticides showed good linearities in the concentration range of 0.05–20 µg/mL with determination coefficients (R²) >0.997. The limits of quantification of eight pyrethroids were 0.004–0.04 mg/kg for green and red pepper and 0.04–0.5 mg/kg for dehydrated red pepper. These values are below the suggested regulatory maximum residue limits. The mean recoveries ranged between 79.0 and 104%, and the relative standard deviations were <11%. The developed method was successfully applied to commercial samples. Some samples were found to contain pyrethroid pesticides with levels below the legal limits. Copyright © 2015 John Wiley & Sons, Ltd.     

Supercritical fluid extraction and quantitative determination of organophosphorus pesticide residues in wheat and maize using gas chromatography with flame photometric and mass spectrometric detection

An automated method using supercritical CO2 and clean-up by solid-phase extraction (SPE) using graphitized carbon black, has been developed for the quantitative determination of organophosphorus pesticide (OPP) residues in wheat and maize. Recoveries were as good as, or better than, those obtained using liquid extraction (LE) and gel permeation chromatography (GPC) for 10 OPP's spiked at levels equivalent to 0.05 and 0.50 microg/g. Lower limits of detection were possible using supercritical fluid extraction (SFE). Incurred residues were found in wheat and maize samples, and good agreement was obtained using SFE+SPE and LE+GPC. The SFE+SPE method required less analyst time and organic solvent, and hazardous waste was reduced.     

气相色谱-负化学源质谱法测定蔬菜中17种拟除虫菊酯类农药残留量

建立了气相色谱-负化学源质谱检测蔬菜中17种拟除虫菊酯类农药残留量的方法。样品中的目标物经乙腈提取后,用乙二胺-N-丙基甲硅烷(PSA)和石墨化炭黑填料进行分散固相萃取净化,气相色谱-负化学源质谱选择离子监测模式测定,同位素内标法定量。在甜豌豆、绿花菜和大葱基质中均未见干扰所有农药测定的现象。17种拟除虫菊酯类农药的定量限均为0.02～5 μg/kg。在10、20、30和100 μg/kg等4个添加水平下,所有农药的回收率均为71.0%～139.0%,相对标准偏差≤12.8%。该方法可作为蔬菜中17种菊酯类农残检测的确证方法。     

Simultaneous determination of multiresidual phenyl acetanilide pesticides in different food commodities by solid‐phase cleanup and gas chromatography‐mass spectrometry

An efficient and sensitive multiresidue method has been developed for quantification and confirmation of 25 phenyl acetanilide pesticides in a wide variety of food commodities including maize, spinach, mushroom, apple, soybean, chestnut, tea, beef, cattle liver, chicken, fish, and milk. Analytes were extracted with acetone–n‐hexane (1:2, v/v) followed by cleanup using SPE. Several types of adsorbents were evaluated. Neutral aluminum and graphitized carbon black cartridge showed good cleanup efficiency. The extract was determined by GC‐MS in the selected ion monitoring mode using one target and two qualitative ions for each analyte. The limits of detection were 0.01 mg/kg for all analytes. The average recoveries ranged from 66.9 to 110.6% (mean 88.8%) and RSDs were in the range 2.0–19% (mean 10.5%) across three fortification levels. The proposed method was successfully applied to real samples in routine analysis and a satisfactory result was obtained.     

Determination of Pyrethroids in Dendrobium officinale by Ultrasound/Microwave-Assisted Solid–Liquid–Solid Dispersive Extraction,Gas Chromatography,and Triple-Quadrupole Mass Spectrometry

An ultrasound/microwave-assisted solid–liquid–solid dispersive extraction method was developed for the determination of 16 pyrethroid insecticides in Dendrobium officinale. The extraction and purification were performed in one step. The pyrethroids were extracted with 8:2 acetone:hexane and purified with a mixture of primary secondary amine, Florisil, C18, and graphitized carbon black. The extraction temperature, extraction time, and ultrasound power were optimized. Trans-cyfluthrin-d₆ was used as the internal standard to improve the accuracy. Under the optimized conditions, the recoveries of the pyrethroids were from 72.2 to 113.9% with the limits of detection between 0.29 and 9.38?µg?kg^?1. The optimized method was successfully used for the determination of pyrethroids in commercial D. officinale samples and may allow monitoring pyrethroids in herbal products.     

Identification and quantitation of pyrethroid pesticide residues in vegetables by solid-phase extraction and liquid chromatography/electrospray ionization ion trap mass spectrometry

A quantitative method consisting of solid-phase extraction (SPE) followed by liquid chromatography/electrospray ionization ion trap mass spectrometry (LC/ESI-ITMS) analysis was developed for the identification and quantitation of ten pyrethroid pesticides commonly used in vegetables. The best HPLC separation was achieved using a gradient program of methanol/water mixture. For the vegetable samples, an SPE procedure to clean up the matrices was carried out prior to LC/MS analysis. Under the optimum conditions, the limits of quantification of the pyrethroid pesticides (tetramethrin, allethrin, fenpropathrin, lambda-cyhalothrin, cypermethrin, deltamethrin, fenvalerate, bioresmethrin, permethrin and bifenthrin) ranged from 0.03 to 0.1 mg kg-1 with relative standard deviations<20%, and the mean recoveries ranged from 69.5 to 102.5%. The proposed method has been successfully applied to the determination of pyrethroids in six vegetables with satisfactory results.     

气相色谱法测定苹果和土壤中的高效氯氟氰菊酯

建立了改进的QuEChERS-气相色谱检测苹果和土壤中高效氯氟氰菊酯残留的分析方法,考察和评价了苹果和土壤两种基质对高效氯氟氰菊酯的基质效应。苹果和土壤样品均用乙腈提取,经石墨化碳黑（GCB）净化后直接进样分析。结果表明：在优化后的QuEChERS条件下,高效氯氟氰菊酯在0.05~10 mg/L范围内线性关系良好,相关系数（R²）大于0.999,检出限为0.12~0.15 μg/kg,定量限为0.38~0.50 μg/kg。用基质标准曲线定量时,高效氯氟氰菊酯在土壤和苹果中的回收率分别为88.29%~97.65%和80.70%~98.69%。苹果和土壤样品对高效氯氟氰菊酯都表现出基质增强效应。该方法的回收率均能达到残留分析要求,用基质配制标准溶液能够有效、方便地校正气相色谱-电子捕获检测器测定高效氯氟氰菊酯残留时的基质效应,且能应用于苹果和土壤实际样品的检测。     

基于多壁碳纳米管改进QuEChERS法结合气相色谱-串联质谱检测茶叶中10种拟除虫菊酯类农药残留

利用多壁碳纳米管(MWCNTs)QuEChERS法提取茶叶中拟除虫菊酯类残留农药,采用气相色谱-串联质谱(GC-MS/MS)分析测定,建立了一种灵敏度高、可靠性强的茶叶中农药残留检测方法。比较了单壁碳纳米管(SWCNTs)、MWCNTS、氨基化多壁碳纳米管和石墨烯4种碳纳米材料和其不同用量下的净化效果;采用正交试验设计对前处理最佳实验条件进行筛选,并对实验影响因素进行方差分析。结果表明:提取溶剂、碳纳米材料种类对10种拟除虫菊酯类农药回收率的影响具有极显著统计学差异(p<0.001),提取时间对回收率的影响有统计学差异(p<0.05),碳纳米材料用量对回收率影响不显著(p>0.05);最佳样品前处理条件为以乙腈为提取溶剂,超声提取35 min,净化剂为60 mg MWCNTs、200 mg PSA和200 mg C18。方法学考察表明,10种拟除虫菊酯类农药在0.01~2 mg/L范围内线性良好;检出限(LOD)为0.001~0.01 mg/kg,定量限(LOQ)为0.005~0.04 mg/kg;绿茶样品空白基质加标试验中,10种农药的回收率为91.4%~109.7%,相对标准偏差为0.12%~9.80%(n=6)。对花茶、绿茶、红茶3种茶叶基质进行基质效应(ME)评价,结果发现净化剂中加入MWCNTs在绿茶和红茶基质中能有效降低ME。利用该方法检测了市售120份茶叶中拟除虫菊酯类农药的残留,多个样品中检出目标物,但均未超标。该方法检测灵敏度高,可靠性好,具有良好的回收率和稳定性,能满足茶叶中农药残留快速定量分析的要求。     

Analysis of sediment-associated insecticides using ultrasound assisted microwave extraction and gas chromatography-mass spectrometry

An ultrasound assisted microwave extraction (UAME) method was developed to simultaneously extract five organophosphate (OP) and eight pyrethroid insecticides from sediment. The optimized UAME conditions were to use 100 ml of a mixture of hexane and acetone (1:1, v/v) solution as the extraction solvents, and extraction time, microwave and ultrasonic power settings of 6 min, 100 W and 50 W, respectively. Extracts were cleaned using solid phase extraction and analyzed by gas chromatography-mass spectrometry in negative chemical ionization mode and quantification was based on matrix-matched standard solutions along with internal standard calibration. At the spiked concentrations of 1, 5 and 20 ng/g dry weight (dw), recoveries of OPs were 77.6-122%, 65.2-128% and 75.6-141% with relative standard deviations (RSDs) of 10.6-18.1%, 3.1-12.5% and 8.0-35.3%, respectively, while recoveries of pyrethroids were 78.0-101%, 76.4-104% and 71.0-99.5% with RSDs of 10.3-23.5%, 4.7-17.6% and 8.8-18.7%, respectively. Method detection limits ranged from 0.31 to 0.45 ng/g dw for the OP insecticides and from 0.27 to 0.70 ng/g dw for the pyrethroid insecticides. The newly developed UAME method was validated by comparing it to Soxhlet and sonication extraction methods. Better recoveries were achieved for most OPs by the novel UAME method, whereas there was no significant difference in recoveries for most of the pyrethroids. Finally, the UAME method was used to quantify the target insecticides in field-contaminated sediment samples which were collected in Guangzhou, China.     

Microwave-assisted extraction and large-volume injection gas chromatography tandem mass spectrometry determination of multiresidue pesticides in edible seaweed

A microwave-assisted extraction method followed by clean-up with solid-phase extraction (SPE) combined with large-volume injection gas chromatography–tandem mass spectrometry (LVI-GC-MS/MS) for the analysis of 17 pesticides in wild and aquaculture edible seaweeds has been developed. An experimental central composite design was employed to evaluate the effects of the main variables potentially affecting the extraction (temperature, time, and solvent volume) and to optimize the process. The most effective microwave extraction conditions were achieved at 125 °C and 12 min with 24 mL of hexane/ethyl acetate (80:20). SPE clean-up of the extracts with graphitized carbon and Florisil, optimized by means of the experimental design, proved to be efficient in the removal of matrix interferences. The analytical recoveries were close to 100% for all the analytes, with relative standard deviations lower than 13%. The limits of detection ranged from 0.3 to 23.1 pg g⁻¹ and the limits of quantification were between 2.3 and 76.9 pg g⁻¹, far below the maximum residue levels established by the European Union for pesticides in seaweed. The results obtained prove the suitability of the microwave-assisted extraction for the routine analysis of pesticides in aquaculture and wild seaweed samples.     

分散固相萃取-在线凝胶色谱-气相色谱-质谱联用法快速检测紫菜中的农药多残留

建立了紫菜中农药多残留的在线凝胶色谱-气相色谱-质谱联用（GPC-GC/MS）检测方法。以有机氯、有机磷、三嗪类和菊酯类的19种农药为目标物,对比了丙酮、丙酮/二氯甲烷（1:1,v/v）和乙腈3种有机溶剂的提取效果,通过石墨化炭黑粉（GCB）和N-丙基乙二胺粉（PSA）分散固相萃取净化和GPC在线净化,气相色谱-质谱联用法分析,外标法定量。结果表明,此方法实现了在线净化与分析检测的自动化,缩短了分析时间。分析物在10~1000 μg/L范围内线性关系良好,相关系数r>0.995;采取GPC大体积进样和气相色谱进样口的程序升温方式提高了检测灵敏度,检出限为0.005~0.03 mg/kg。方法的平均添加回收率在70%~120%之间,相对标准偏差（RSD）均小于15%。该方法简单、快速、具有良好的回收率和重复性,适用于紫菜样品中农药多残留的快速灵敏检测。     

Rapid analysis of pyrethroid insecticides in aquaculture seawater samples via membrane-assisted solvent extraction coupled with gas chromatography-electron capture detection

A simple, efficient, and environmentally friendly membrane-assisted solvent extraction (MASE) method for the extraction and preconcentration of six pyrethroid insecticides from aquaculture seawater samples followed by gas chromatography-electron capture detection (GC-ECD) was successfully proposed. The operating conditions for MASE, such as the extraction solvent, solvent volume, NaCl concentration, stirring rate, extraction time, and temperature, were optimized. Compared to conventional Florisil-solid phase extraction (SPE), higher extraction recoveries (85.9% to 105.9%) of three spiked levels of the six pyrethroid pesticides in aquaculture seawater were obtained using MASE, and the RSD values were lower than 7.9%. The limits of detection (LOD, signal-to-noise ratio (S/N)=3) and quantification (LOQ, S/N = 10) were in the range of 0.037-0.166 and 0.12-0.55 μg L(-1), respectively. The results demonstrate the excellent applicability of the MASE method in analyzing the six pyrethroid pesticides in aqueous samples. The proposed method exhibited a high potential for routine monitoring analysis of pyrethroid insecticides in seawater samples.     

固相萃取-气相色谱-质谱法测定木制家具中氯酚类及菊酯类防腐剂

建立了固相萃取-气相色谱-质谱(SPE-GC-MS)检测含氯酚类化合物(2,4-二氯苯酚、2,4,6-三氯苯酚、2,4,5-三氯苯酚、2,3,4,6-四氯苯酚、五氯苯酚、林丹)和菊酯类化合物(氯菊酯、氟氯氰菊酯、氯氰菊酯、溴氰菊酯)等10种木材防腐剂的方法。对家具样品采用超声萃取法、以甲醇为提取剂在室温下反复提取2次,提取液经浓缩后,加入碳酸钾和乙酰酐衍生化,将衍生化后的溶液通过Oasis HLB固相萃取柱净化,用乙酸乙酯洗脱并收集检测。采用该方法实现了家具中10种木材防腐剂的分离检测,该方法中氯酚类防腐剂定量限为1 mg/kg、菊酯类防腐剂定量限为5 mg/kg,平均回收率为76.0%～108.8%。应用该方法对市场上销售的木制家具进行了检测,在部分家具中检出含有少量林丹。实验结果证明,该方法准确、灵敏,可有效地应用于木制家具中防腐剂的实际检验工作中。     

纳米纤维在分析菊酯类农药残留中的应用

以电纺聚苯乙烯纳米纤维作固相萃取材料,对茶叶样品中的拟除虫菊酯农药进行分离富集,用气相色谱-电子捕获器进行检测,并对影响纤维萃取效率的因素进行优化,联苯菊酯、氯菊酯、氰戊菊酯、溴氰菊酯和甲氰菊酯在纳米纤维柱上的最大吸附量分别为7.8、7.5、7.2、6.6、7.0μg/mg,5种农药的3种标准混合液通过纳米纤维小柱后回收率为65.5%～89.0%,RSD为1.2%～3.0%。测定喷洒5种农药后的茶叶样品添加回收率为61.3%～87.1%,RSD为0.9%～2.8%,方法的测定下限为1.0×10-4～1.0×10-2mg/kg。该方法可以满足茶叶中拟除虫菊酯类农药残留检测的要求。     

Rapid preconcentration method for the determination of azadirachtin-A and -B, nimbin and salannin in neem oil samples by using graphitised carbon solid phase extraction

A simple and rapid method involving solid phase extraction and liquid chromatography for the determination of azadirachtin-A and -B, nimbin and salannin at nanogram levels in neem oil samples is presented. The neem oil samples are defatted and the compounds of interest extracted by mixing the sample with hexane and passing the hexane solution through a graphitised carbon black column. After washing the column with 2 ml of hexane, azadirachtin-A and -B, nimbin and salannin are eluted with 5 ml of acetonitrile and quantified using HPLC with UV detection. The recoveries of azadirachtin-A and -B, nimbin and salannin in fortified oil samples were 97.4-104.7%. The upper limit of quantification is up to 100 micrograms ml-1 without any additional clean-up and with little interference from lipids during the analysis by HPLC. The method was successfully applied to various neem oil samples collected from different locations in India.     

Simultaneous determination of base/neutral and acid herbicides in natural water at the part per trillion level

Summary A new method for the simultaneous identification and quantification of base/neutral and acidic pesticides at a low nanogram per liter concentration level in natural waters is presented. The method includes enrichment of the compounds by solid phase extraction on graphitized carbon black, followed by sequential elution of the base/neutral and acidic pesticides. Identification and quantification of the compounds is performed with HPLC-ESI-MS. This procedure involves passing 1 L of ground water and 2 L of drinking water samples through a 0.5 g graphitized carbon black (GCB) extraction cartridge. A conventional 4.6-mm-i.d. reversed phase LC C-18 operating with a 1 mL min⁻¹ flow of the mobile phase was used to chromatograph the analytes. A flow of 100 μL min⁻¹ of the column effluent was diverted to the ESI source. The ESI source was operated in positive ion mode for base/neutral pesticides and in negative-ion mode for acid pesticides. For the analyte considered, the response of the mass detector was linearly related to the amount of the analytes injected between 5 and 250 ng. In all cases, recoveries of the analytes were better than 90%. The limit of detection (signal-to-noise ratio=3) of the method for the pesticides considered in drinking water samples was estimated to be about 3–10 ng L⁻¹.     

Low-temperature clean-up method for the determination of pyrethroids in milk using gas chromatography with electron capture detection

This paper describes a new gas-chrormatography with electron capture detection (GC-ECD) method for determination of some pyrethroids in milk samples. The extraction of the pyrethroids was carried out by liquid–liquid extraction with clean-up by precipitation at low temperature, without additional stages for removal of fat interferences. The method was efficient with recoveries of 93.0 ± 0.1% for cipermethrin and 84.0 ± 0.3% for deltamethrin. The quantification limits were 0.75 μg L⁻¹ for both pyrethroids. The method was simple, of easy execution, and used only small quantities of organic solvent. After optimization and validation, the method was used for the determination of residues of the pyrethroids cipermethrin and deltamethrin in milk and in lactea drink commercialized in Viçosa (MG, Brazil). Some samples presented contamination with deltamethrin at levels below the maximum contamination limits established by the FAO.     

亚临界水萃取及气相色谱-串联质谱法检测红茶中多种农药残留

建立了亚临界水萃取及气相色谱-串联质谱(GC-MS/MS)检测红茶中21种有机氯和拟除虫菊酯农药残留的方法。在萃取压力为5 MPa条件下,样品经150 ℃的亚临界水提取15 min后,将目标物转移至丙酮-正己烷(1:1, v/v)中,经ENVI-Carb固相萃取净化小柱净化,DB-5毛细管气相色谱柱分离,在多反应监测(MRM)模式下进行MS/MS检测,基质匹配溶液内标法定量。各目标物在5.0～320.0 μg/L范围内线性关系良好,相关系数均大于0.99,其定量限(信噪比(S/N)＞10)为50 ng/g,检出限(S/N＞3)为10 ng/g。茶叶基质中添加50、100和200 ng/g的标准品时,21种农药的回收率为70.18%～119.98%,相对标准偏差(RSD)为5.01%～11.76%。该方法的灵敏度、准确度和精密度均符合农药残留测定的技术要求,适用于红茶中有机氯和拟除虫菊酯农药残留的检测。     

On-line dialysis-SPE-CE of acidic drugs in biological samples

A fully automated method is presented for the determination of acidic drugs in urine and serum using on-line dialysis-solid-phase extraction (SPE)-capillary electrophoresis (CE) with UV detection. With non-steroidal anti-inflammatory drugs (NSAIDs) as test compounds, detection limits in the biological samples were 0.05-1.0 microgram ml-1. Calibration plots were linear over two orders of magnitude and the within-day and between-day repeatability were better than 10%. The CE capillary and SPE column were used for over 500 analyses; the dialysis membrane was replaced after 250 analyses. A general protocol for dialysis-SPE-CE which can be used for amphoteric and acidic drugs was devised. The present results show that this protocol has general validity and can be recommended for future work on other classes of drugs.     

Determination of linezolid in human plasma by LC-MS-MS

A rapid, sensitive and selective LC-atmospheric pressure-chemical ionization-MS-MS method for the determination of the new antimicrobial agent, linezolid, in human plasma using selected reaction monitoring (SRM) was developed. Linezolid and the internal standard were extracted from the biological samples by solid phase extraction (SPE) and analyzed on a reversed-phase Shim Pack CLC-CN, C18 column with the mobile phase of acetonitrile and 20 mM ammonium acetate solution (4 + 1 v/v). Detection was accomplished using an LCQ mass spectrometer (Finnigan), which was programmed in positive MS-MS mode to permit measurement of the fragment ions of linezolid and internal standard at m/z 296.2 and 223.2, respectively. The assay run-time was less than 3.5 min. Quantitative analysis was based on peak area ratio of linezolid to the internal standard. Calibration plots were established over the concentration range of 0.1-20 micrograms ml-1 of linezolid with the lowest detection limit of 0.05 microgram ml-1 using 10 microliters sample volume. The SPE technique quantitatively recovered linezolid and the internal standard from the plasma samples at a percentage range of 89.1-93.7%. Determination of control samples of linezolid in plasma validated the LC-MS-MS-SRM method. Intra-assay and inter-assay precision were in the range of 5.1-11.4% relative standard deviation, whereas the intra- and inter-accuracy were in the range of 97.5-114.0% of the nominal concentrations of linezolid added. The data confirmed that the plasma samples of linezolid were stable at room temperature and when stored at -20 degrees C for at least 10 d. The developed LC-MS-MS-SRM method is recommended for the determination of linezolid in human plasma.