Multiresidue gas chromatographic method for determining synthetic pyrethroid pesticides in agricultural products: collaborative study

Fourteen laboratories from 6 countries and regions participated in an international collaborative study to evaluate a multiresidue gas chromatographic (GC) method for determining 8 synthetic pyrethroid pesticides in grains, fruits, and vegetables. The study design was based on Youden's matched-pairs principle for collaborative tests of analytical methods. Each laboratory analyzed 12 collaborative samples of wheat, oranges, and tomatoes as blind samples. Wheat samples were extracted with acetonitrile-water (2 + 1), while orange and tomato samples were extracted with acetone. Residues were partitioned into hexane, evaporated to dryness with a rotary evaporator, and then dissolved in hexane. The hexane extract was partitioned with acetonitrile and cleaned up on a 5% water-deactivated Florisil column with 6% ethyl ether in hexane as eluant. Residue concentrations were determined by GC with electron capture detection with splitless injection by comparison with single-point calibration standards. The appropriate standard concentration was determined by screening sample extracts before analysis. The multiresidue method was tested over the concentration range of 0.095-1.909 mg/kg depending on the 8 different of pesticides and agricultural products analyzed in the collaborative study. Statistical analysis of data from 13 laboratories showed weighted average recoveries for 8 pyrethroids in wheat, oranges, and tomatoes at 0.105-1.909, 0.095-1.909, and 0.105-0.954 mg/kg, respectively, ranging from 91.8 to 100.2%, from 88.1 to 100.6%, and from 88.2 to 101.5%, respectively. Reproducibility relative standard deviation values ranged from 6.46 to 17.74%, from 5.94 to 18.13%, and from 5.59 to 10.48%, respectively. Repeatability relative standard deviation values ranged from 6.34 to 10.84%, from 5.19 to 11.72%, and from 3.20 to 8.09%, respectively. The multiresidue GC method for determining synthetic pyrethroid pesticides in agricultural products has been adopted first action by AOAC INTERNATIONAL.     

Determination of residues of 446 pesticides in fruits and vegetables by three-cartridge solid-phase extraction-gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry

A method was developed for determination of residues of 446 pesticides in fruits and vegetables through the use of cleanup by a 3-cartridge solid-phase extraction-gas chromatography/ mass spectrometry (GC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). Fruit and vegetable samples (20 g) were extracted with 40 mL acetonitrile, salted out, and centrifuged. Half of the supernatant was passed into an Envi-18 cartridge, eluted with acetonitrile, and cleaned up with Envi-Carb and aminopropyl Sep-Pak cartridges in series after concentration of the eluates. Pesticides were eluted with acetonitrile-toluene (3 + 1, v/v), and eluates were concentrated to 0.5 mL and then added into internal standards after solvent exchange with 2 mL hexane and used for determination of 383 pesticides by GC/MS. The other half of the supernatant was concentrated to 1 mL and cleaned up with Envi-Carb and aminopropyl Sep-Pak cartridges in series. Pesticides were eluted with acetonitrile-toluene (3 + 1, v/v), and the eluates were concentrated to 0.5 mL, dried with nitrogen gas, diluted to 1.0 mL with acetonitrile-water (3 + 2, v/v), and used for determination of 63 pesticides by LC/MS/MS. The limit of detection for the method was 0.2-600 ng/g depending on the individual pesticide. In the method, fortification recovery tests at high, medium, and low levels were conducted on 6 varieties of fruits and vegetables, i.e., apples, oranges, grapes, cabbage, tomatoes, and celery, with average recoveries falling within the range of 55.0-133.8% for 446 pesticides, among which average recoveries between 60.0-120.0% accounted for 99% of the results. The relative standard deviation was between 2.1-39.1%, of which a relative standard deviation of 2.1-25.0% made up 96% of the results. Experiments proved that the method was applicable for determination of residues of 446 pesticides in fruit and vegetables.     

Multiresidue Analysis of Pesticides in Vegetables and Citrus Fruits by LC–MS–MS

In this work, an analytical multiresidue method using liquid chromatography tandem-mass spectrometry (LC–MS–MS) with triple quadrupole in selected reaction monitoring (SRM) mode for the simultaneous determination of 54 pesticides in vegetables (pepper and tomato) and citrus fruits (orange and lemon) has been developed. The procedure involves initial single phase extraction of sample with acetonitrile by agitation, followed by liquid–liquid partition aided by “salting out” process using NaCl. The average recovery by the LC–MS–MS method obtained for these compounds varied from 65.5 to 114.5% with a relative standard deviation between 2.3 and 8.3%. The method presents good linearity over the range assayed 10–500 μg L^?1 (except famoxadone 50–1,000 μg L^?1) and the detection limits for the pesticides studied varied from 0.03 to 14.9 μg kg^?1. The proposed method was used to determine pesticide levels in vegetables and citrus fruit samples from different experimental orchards and greenhouses from the Region of Murcia.     

蔬菜、水果中多农药残留的筛查

近年来,食品安全问题引起了人们的高度重视,农药残留污染是制约食品安全的重要因素.在食品农药残留检测方法中,农药残留检测的种类越来越多,农药残留的限量标淮越来越严,人们对食品中农药残留的检测正在不断地探索快速准确的有效方法[1].解卷积报告软件(DRS)是由安捷伦公司研发,其目的主要用于农药和可疑内分泌干扰物的筛查.该软件由安捷伦质谱工作站、自动质谱解卷积和鉴定系统(AMDIS)以及NIST检索三部分组成.AMDIS需要使用包含有保留时间的自动质谱解卷积和鉴定系统.DRS能大大提高复杂基质中痕量化合物的定性能力,并且在SCAN和SIM两种模式下均可采用DRS进行数据处理.保留时间锁定(RTL)和RTL数据库是DRS的一个组成部分,它无需使用标样,只需采用数据库中建立的GC/MS条件,即可实现对农药和一些内分泌干扰物分析鉴定.     

Multi-residue pesticide analysis in fruits and vegetables by liquid chromatography-time-of-flight mass spectrometry

In this work, a new multi-residue methodology using liquid chromatography-time-of-flight mass spectrometry (LC-TOF-MS) for the quantitative (routine) analysis of 15 pesticide residues has been developed. The analytical performance of the method was evaluated for different types of fruit and vegetables: pepper, broccoli, tomato, orange, lemon, apple and melon. The accurate mass measurements were compared in different matrices at significantly different concentration levels (from 0.01 to 0.5 mg/kg) obtaining accuracy errors lower than 2 ppm, which is well within the accepted limits for elemental confirmation. Linearity of response over two orders of magnitude was demonstrated (r > 0.99). Matrix effects resulting in suppression or enhancement of the response were frequently observed, most notably in broccoli and citrus. Instrumental limits of detection (LOD) were between 0.0005 and 0.03 mg/kg depending on the commodity and pesticide studied, all being within European Union regulations for food monitoring program. Finally, the methodology was applied to the analysis of two samples from an inter-laboratory exercise. The high degree of confirmation for target pesticides by accurate mass measurements demonstrated the applicability of the method in routine analysis. This study is a valuable indicator of the potential of LC-TOF-MS for quantitative multi-residue analysis of pesticides in vegetables and fruits.     

Determination of Organophosphorus Pesticides in Vegetables by GC with Pulsed Flame-Photometric Detection, and Confirmation by MS

The suitability of gas chromatography with pulsed flame-photometric detection (GC–PFPD) for determination of 24 organophosphorus (OP) pesticides in vegetables has been assessed. Pesticides were extracted with dichloromethane and analyzed without cleanup. The performance of the method was fit for purpose; recovery was between 73 and 110% and precision was better than 15%. Calculated lower limits of detection were typically <0.01 mg kg^?1, much lower than the maximum residue levels stipulated by European legislation. Three pesticides were detected in vegetable samples. Their presence was confirmed by GC with tandem mass spectrometric detection (GC–MS–MS).     

An approach to the application of microwave-assisted micellar extraction and liquid chromatography with ultraviolet detection to the extraction and determination of organophosphorus pesticides in tomato samples

Microwave-assisted micellar extraction methodology was applied to extract a mixture of 8 organophosphorus pesticides from the cuticle of tomato samples prior to analysis by liquid chromatography with ultraviolet detection. This technique provided very good results and was simple, fast, and environmentally friendly. The pesticides under study were extracted using the nonionic surfactants polyoxyethylene 10 lauryl ether (POLE) and oligoethylene glycol monoalkyl ether (Genapol X-080). The optimal extraction variables to be applied were determined for each surfactant and then compared. POLE proved to be the most suitable for the extraction, with recoveries over 70% in the majority and relative standard deviation values under 4.8%. After validation using a tomato sample enriched with a certified mixture, the proposed method was applied to the analysis of organophosphorus pesticides in lettuce and pepper samples.     

高效液相色谱法同时测定蔬菜水果中的12种农药残留

建立了同时测定蔬菜水果中12种农药残留的反相高效液相色谱分析方法。将样品捣碎,用乙酸乙酯超声提取,经Florisil固相萃取柱净化、正己烷-二氯甲烷(体积比为1∶1)洗脱、氮气吹干、甲醇溶解并定容后,采用高效液相色谱柱分离、紫外检测,以外标法定量。结果表明：12种农药标准曲线的线性相关系数范围为0.9985~0.9999;检测限为0.14~2.65 ng;在水果中的平均加标回收率为62.2%~118.2%,相对标准偏差(RSD)为0.56%~11.8%;在蔬菜中的平均加标回收率为52.1%~124.6%,RSD为0.89%~18.4%。用所建立的方法成功地测定了白菜、莲白、黄瓜、苹果、梨等40份样品中的农药残留。方法具有快速、简便、准确、灵敏、重现性较好的特点,适合于蔬菜水果样品中多种微量农药残留的测定。     

多壁碳纳米管固相萃取净化气相色谱法分析蔬菜中有机氯和拟除虫菊酯农药残留

建立了多壁碳纳米管为吸附剂的固相萃取(SPE)净化、气相色谱-电子捕获检测(GC-ECD)测定蔬菜中6种有机氯和7种拟除虫菊酯农药的方法。采用双柱(HP-50和HP-1色谱柱)双检测器进行定性和定量分析。蔬菜样品采用乙腈提取,多壁碳纳米管SPE柱净化,正己烷溶解上样,丙酮-正己烷(7:3, v/v)洗脱,13种农药中有11种农药的添加回收率高于70%。将该净化方法用于荷兰黄瓜、卷心菜、红圣女果、奶油生菜、紫甘蓝、韭菜、大葱和洋葱等样品的净化,与弗罗里硅土SPE柱相比较,净化效果更好,表明多壁碳纳米管具有较强的吸附去除色素的能力,可以避免色素对测定的干扰。     

QuEChERS-超高效液相色谱-串联质谱法测定蔬菜中41种农药残留

采用QuEChERS-超高效液相色谱-串联质谱技术,建立了蔬菜中常见的隐性农药、禁限用农药、植物生长调节剂等检出率较高的41种农药残留的测定方法。蔬菜样品用1%(v/v)乙酸-乙腈溶液提取,乙二胺-N-丙基硅烷(PSA)净化后直接进样分析,采用正、负离子多反应监测(MRM)模式,外标法定量。结果表明,在优化后的QuEChERS、色谱和质谱条件下,41种农药在1.0~100 μg/L范围内线性关系良好,相关系数(r²)大于0.999,检出限为0.003~1.00 μg/kg,不同基质中的平均回收率范围为74.1%~120.4%,相对标准偏差(RSD)范围为2.8%~11.9%。该方法快速简便、灵敏度高、净化效果好,可用于蔬菜中41种农药的快速测定,为蔬菜质量安全风险评估工作提供了有力保障。     

Application of single-drop microextraction coupled with gas chromatography for the determination of multiclass pesticides in vegetables with nitrogen phosphorus and electron capture detection

In the present work the single-drop microextraction (SDME) technique coupled with GC-NPD and GC-ECD was evaluated for the determination of multi-class pesticides in vegetables. The donor sample solution preparation was optimized by testing different mixtures of solvents and dilutions with water. The SDME procedure was optimized by controlling drop organic solvent, drop volume, agitation, and exposure time. The optimum sample preparation was achieved with the use of a mixture of acetone/H(2)O (10/90, v/v) in donor sample solution preparation and the consequent SDME using a toluene drop under mild stirring for 25min. The efficiency of the extraction process was studied in fortified tomato and courgette samples and matrix effects were further estimated. The proposed method showed good linearity, limits of detection at the sub-microgkg(-1) level and high precision (RSD <15%) and was applied with success in real vegetable samples showing that SDME can be a promising way for sample preparation in pesticide residue analysis.     

Screening Method for the Determination at Parts Per Trillion Levels of Pesticide Residues in Vegetables Combining Solid‐Phase Microextraction and Gas Chromatography‐Tandem Mass Spectrometry

Abstract

A new analytical method is proposed for determining residues of 70 pesticides of different chemical families at parts per trillion levels in fresh vegetables. For that, only 4 g of the vegetable samples were quickly extracted with 10 ml of ethyl acetate. The method is based on a vanguard/rearguard strategy that reduces the average time required per sample when the method is applied to a high number of vegetable samples in a quality control laboratory. At the beginning, an aliquot of the extract is evaporated and re‐dissolved in a mixture water:acetone (9∶1 v/v). For screening purposes, the pesticides were extracted for only 10 min by direct immersion of a solid‐phase microextraction (SPME) fiber (65 µm polydimethylsiloxane‐divinylbenzene, PDMS‐DVB). The SPME device was automated and on‐line coupled to a gas chromatograph with an ion trap mass spectrometer (GC‐MS) operated in full scan mode for screening in less than 18 min those samples that potentially contain pesticides above 0.01 mg kg^?1 (cut off value). After that, only those potentially non‐negative samples were reanalyzed by a sensitive quantifying/confirming method that re‐extract by SPME the pesticides in 55 min of absorption and determine them by GC with tandem MS (MS/MS). The method has been validated following EU guidelines and compared with a conventional extraction method based on the use of higher amounts of organic solvents. The limits of detection (LOD), confirmation (LOC) and quantitation (LOQ) as well as the calibration curves obtained allowed the determination of the target pesticides at concentrations clearly below the maximum residue levels (MRL) stated by EU being possible the determination of parts per trillion of the pesticides in ecological (green) vegetables. The method has been applied to the analysis of real samples and the results compared with those obtained by a conventional extraction method accredited by ENAC (Spanish Accreditation Body). The proposed method was also evaluated participating in a proficiency test with adequate results (z‐score among±2).     

程序升温大体积进样和解卷积气相色谱-质谱法测定蔬菜水果中32种农药残留量

建立了蔬菜、水果中有机磷、有机氯、拟除虫菊酯和氨基甲酸酯等32种农药的气相色谱-质谱(GC-MS)检测方法。样品经乙腈提取,石墨碳黑串联丙氨基固相萃取柱净化,采用程序升温大体积进样,GC-MS全扫描模式采集,结合解卷积技术定性分析,内标法定量。分别对程序升温和大体积进样等条件进行了研究,并考察了方法选择性和耐用性。在最优条件下,32种农药的响应值与浓度呈良好的线性关系(r>0.995),各农药的方法检出限为2.0~5.0 μg/kg,以菠菜、四季豆和黄瓜为代表基质,进行3个水平(0.010~0.50 mg/kg)的加标回收试验(n=6),回收率为65.2%~120.3%,相对标准偏差(RSD)为4.1%~22.3%。该方法快速、灵敏、可靠、耐用,能满足蔬菜、水果中多类多残留痕量分析的要求。     

Application of hollow fiber supported liquid membrane extraction to the simultaneous determination of pesticide residues in vegetables by liquid chromatography/mass spectrometry

A new analytical procedure using a hollow fiber supported liquid membrane (HFSLM) has been developed for the simultaneous determination of pesticide residues in vegetables by liquid chromatography (LC) coupled with electrospray mass spectrometry (MS). The extraction technique requires minimal sample preparation and solvent consumption. Optimum extraction conditions have been evaluated with respect to sample pH, ionic strength, liquid membrane composition, extraction time, stirring rate and acceptor composition. The extraction method has been validated for matrices such as cucumber, tomato and pepper, indicating that cucumber can be selected as representative matrix for routine analysis of these food commodities. Linear ranges of pesticides in vegetable samples were 10 to 200 microg/kg, and the repeatability of the method was less than 20% for the lowest calibration point. The limits of detection ranged from 0.06 to 2.7 microg/kg and the limits of quantification from 0.2 to 9.0 microg/kg, which were low enough to determine the pesticide residues at concentrations below or equal to the maximum residue levels (MRLs) specified by European Union. The method was finally applied to the determination of more than 20 pesticides in market vegetable samples and the concentrations found in these samples were always lower than the MRLs. This new approach can be considered as a powerful alternative to the traditional extraction techniques.     

A new analysis method with GC or GC-MS for the quick detection of pesticide residues in vegetables

A new analytical method for gas chromatography (GC) or GC-mass spectrometry (MS) using the direct sampling technique is described. This direct sampling technique, which bypasses the conventional complicated sample pretreatment process, is applicable to cases of fast detection of pesticide residues in foods and large-scale screening of samples by portable GC in field detection. By a direct sampling technique, the vegetable sample is ground into paste, and 30 mg is placed directly into the evaporating chamber for GC-MS identification and quantitation (by full-scan mode). The GC column used is an HP-5 (30.0-m x 250-microm x 0.25-microm, 5% phenyl methyl siloxane). Chlorpyrifos, bromophos, fenpropathrin, gamma-666, and pp'-DDT are chosen to represent organophosphorus, pyrethrins, and organochlorine pesticides because they are chief objects of the detection of pesticide residues in vegetables. Rape, a common and mass-consumed vegetable in China, is chosen as the sample in this study. The detection limits for these pesticides by the full-scan mode are all below the maximum pesticide residue limit of vegetables set by the Ministry of Agriculture of China, and the reproducibility of this method is acceptable. This analysis method is proven to be simple, quick, and reliable and is suitable for multipesticide residues analysis of vegetables. It can also be used in the analysis of vegetable components and signal chemicals.     

Method validation of resistive heating--gas chromatography with flame photometric detection for the rapid screening of organophosphorus pesticides in fruit and vegetables

A rapid method for the screening of organophosphorus (OP) pesticides in fruit and vegetables is reported. Sample extracts were analysed using resistive heating-gas chromatography (RH-GC) with flame photometric detection (FPD). A CarboFrit insert in the GC liner allowed injection of crude extracts onto the GC system. Separation of up to 20 pesticides was achieved in 4.3 min with excellent retention time stability. Signal-to-noise ratios of 5:1 or better were obtained for the majority of the pesticides at the lowest calibrated level (LCL), 0.01 microg ml(-1), with excellent linearity over the range 0.01-0.5 microg ml(-1) (0.004-0.2 mg kg(-1) equivalent). Average recoveries between 70 and 116% were obtained for pesticides spiked at 0.01 and 0.1 mg kg(-1) with associated R.S.D. values < or =20% in the majority of cases. Estimates of relative reproducibility standard deviation (R.S.D.(R)), made by combining observed R.S.D. values with estimates of uncertainty associated with mean recovery allowed the determination of HORRAT values which confirmed that the method is capable of producing results which are fit for purpose. The validated method was then used to screen peaches, grapes and sweet peppers for a total of 37 pesticides. Incurred residue results obtained using RH-GC-FPD were in good agreement with the results from analysis of the same samples using MS confirmation.     

Splitless large-volume GC-MS injection for the analysis of organophosphorus and organochlorine pesticides in vegetables using a miniaturised ethyl acetate extraction

A simple, rapid and sensitive multiresidue method has been developed for the determination of ten organophosphorus and organochlorine pesticides, commonly used in crop protection. The analysis uses a miniaturised extraction with ethyl acetate followed by large volume injection (10 microL) GC-EI-MS analysis in SIM (selective ion monitoring) mode. Sensitivity and selectivity of the method were acceptable with limits of detection (LODs) lower than 0.01 mg kg-1, except for endosulfan alpha and beta (0.05 mg kg-1). Average recoveries of between 63-99% were obtained and good linearity was observed in the range from 0.01 to 1.00 mg kg-1. Repeatability and reproducibility studies yielded relative standard deviations lower than 20% in all the cases. The method was applied to the analysis of 110 tomato, pepper and cucumber samples, as part of the monitoring programme of the Association of Producers and Exporters of Fruits and Vegetables of Almería.     

Screening and confirmation of 100 pesticides in food samples by liquid chromatography/tandem mass spectrometry

An analytical method for screening, quantitation and confirmation of a group of 100 pesticides in vegetable and fruit samples was developed using liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS). The pesticides studied belonged to different chemical families of herbicides, insecticides and fungicides; some degradation products were included as well. A thorough optimization was performed for each analyte to achieve individual optimum fragmentor and collision energy voltages. Two transitions per parent compound were monitored in a single chromatographic run containing two time segments. A small particle size C(18) column (1.8 microm) was used for the chromatographic separation of the mixture, providing very narrow peaks and allowing an excellent separation of all the analytes in a 30-min period for maximum peak capacity. The method was validated with blank matrices of green pepper, tomato and orange spiked from 0.1 to 100 microg/kg with the pesticide mix. Quantitation was carried out using matrix-matched standard calibration and linearity of response over 3 orders of magnitude was demonstrated (r > 0.99). Limits of detection based on two transitions and ion-ratio requirements ranged between 0.3 and 50 microg/kg. In general, the sensitivity obtained meets the maximum residue levels (MRLs) established by the European Union regulation for food monitoring programs. The analytical performance of the method was evaluated for different types of vegetables and fruits, showing little or no matrix effects, and examples of screening and confirmation of pesticides in these samples are shown here.     

介孔氧化铝净化-气相色谱法同时测定蔬菜、水果及茶叶中16种有机磷农药残留

利用气相色谱检测技术,建立了能应用于白菜、生菜、南瓜、洋葱、番茄、白萝卜、苹果、梨及茶叶等不同基质中16种有机磷农药残留的检测方法。样品采用乙酸乙酯提取,经以合成的介孔氧化铝作吸附剂的固相萃取柱净化,DB-1701毛细管柱分离,气相色谱-火焰光度检测器检测。结果表明,蔬菜、水果及茶叶基质中16种有机磷农药在10~2000 μg/L范围内具有良好的线性关系（R²>0.997）;平均回收率为83.2%~103.8%,相对标准偏差为2.0%~9.9%。该方法灵敏度高、准确度高、重复性好,可适用于蔬菜、水果及茶叶基质中16种有机磷残留量的同时测定。     

Determination of nitrogen- and phosphorus-containing pesticide residues in vegetables by gas chromatography with nitrogen-phosphorus and flame photometric detection after gel permeation chromatography and a two-step minicolumn cleanup

An efficient and reliable multiresidue method for determining pesticide residues in a large number of vegetable samples was studied. First, the important target compounds for monitoring, 52 nitrogen- and/or phosphorus-containing pesticides, were selected. The sample was extracted with acetonitrile, and the separated acetonitrile layer was cleaned up by a salting-out step. The acetonitrile extract was purified by gel permeation chromatography that divided the pesticide eluate into 2 fractions; the pesticide fractions were respectively purified by a 2-step minicolumn cleanup in which the second pesticide fraction was loaded on a silica-gel minicolumn. After a Florisil minicolumn was inserted on the silica-gel minicolumn, the first pesticide fraction was loaded on the tandem minicolumn, which was eluted with acetone-petroleum ether (3 + 7). The combined eluate was subjected to dual-column gas chromatography (GC) with nitrogen-phosphorus and flame photometric detection. By application of the optimum cleanup conditions to the 52 pesticides selected, good resolution and low breakdown levels of the pesticides during GC were maintained. Recoveries of the 52 pesticides from fortified cabbage, lettuce, spring onion, and spinach ranged from 72 to 108% with relative standard deviations of 2-17%, except for the recoveries of methamidophos and chlorothalonil. The detection limits of the pesticides were satisfactory (0.001-0.009 mg/kg) for monitoring pesticide residues in vegetables.