Multiresidue method for determination of 90 pesticides in fresh fruits and vegetables using solid-phase extraction and gas chromatography-mass spectrometry

A multiresidue method for analysis of 90 pesticides with different physico-chemical properties in fruits and vegetables was developed. The method involves a rapid and small-scale extraction procedure with acetone using vortex mixing. Solid-phase extraction (SPE) on a highly cross-linked polystyrene divinylbenzene column (LiChrolut EN) was used for clean-up and pre-concentration of the pesticides from the water-diluted acetone extracts. For most fruit and vegetable samples this partial clean-up was sufficient, but some of them with more co-extracting substances need further clean-up (cereals, spinach, carrots, etc.). Diethylaminopropyl (DEA) modified silica was used for efficient removal of interferences caused by various organic acids, sugars, etc. The pesticide residues were determined by gas chromatography with a mass selective detector (GC-MS). The majority of pesticide recoveries for various fruits and vegetables were >80% in the concentration range from 0.01 to 0.50 mg/kg, except for the most polar pesticides (methamidophos, acephate, omethoate) which cannot be determined by this method. The limit of quantitation for most of the pesticides was 0.01 mg/kg with majority of relative standard deviations (R.S.D.s) below 10%.     

Multiresidue method for the gas chromatographic determination of pesticides in honey after solid-phase extraction cleanup

A new multiresidue method is described for the determination of pesticides in honey. The method involves dissolution of the honey in a methanol-water mixture, followed by solid-phase extraction cleanup and gas chromatographic determination. Twenty-six pesticides used on flowering field crops, on flowering fruit and vegetables, or as acaricides to control Varroa jacobsoni in beehives are determined by the method. Recoveries from honey, spiked at 0.02-1.6 mg/kg, ranged from 85 to 127% with a relative standard deviation (RSD) of 2-16%, except for the RSD of 27% for captan at 0.05 mg/kg.     

Capillary electrophoresis for analyzing pesticides in fruits and vegetables using solid-phase extraction and stir-bar sorptive extraction

Two procedures based on solid-phase extraction (SPE) and stir-bar sorptive extraction (SBSE) in combination with micellar electrokinetic chromatography (MEKC)--diode array detection (DAD) were compared for the simultaneous extraction of acrinathrin, bitertanol, cyproconazole, fludioxonil, flutriafol, myclobutanil, pyriproxyfen, and tebuconazole in lettuce, tomato, grape, and strawberry. Selectivity and resolution of the MEKC procedure were studied changing the pH and the molarity of the buffer, the type and the concentration of surfactant, and the methanol content in the mobile phase. A buffer consisting of 6 mM sodium tetraborate decahydrate with 75 mM of cholic acid sodium solution (pH 9.2) gave the best results. Linearity, extraction efficiencies and limits of quantitation (LOQs) of both extraction methods were compared. The recoveries obtained by SPE ranged from 40 to 106% with relative standard deviations (R.S.D.s) from 10 to 19% whereas by the SBSE method, the recoveries were 12-47% and the R.S.D.s 3-17%. The LOQs were much better by SPE (0.2-0.5 mg kg(-1) depending on the processed sample amount) than those obtained by SBSE (1 mg kg(-1) for each compound). Advantages and disadvantages of both procedures are also discussed. As SPE is more robust, rapid, and sensitive than SBSE, its application in combination with MEKC is recommended because provided LOQs below the MRLs established, which is not always attained by SBSE.     

蔬菜、水果中12种限量有机磷农药残留量测定方法

建立了蔬菜、水果中12种限量有机磷农药的提取、净化及毛细管柱气相色谱测定法。目标农药经乙腈萃取,弗罗里硅土柱净化,浓缩后用带火焰光度检测器(FPD)的双塔双柱气相色谱测定,前柱(DB-17)定量,后柱(DB-1)定性。12种农药线性良好,线性相关系数大于0.9990,对蔬菜、水果添加0.01～0.1mg/kg的水平,12种有机磷的平均回收率在70.9%～119.9%之间,相对标准偏差0.12%～12%,本方法的最低检测限0.005～0.05mg/kg。     

Multiresidue analysis of pesticides in vegetables and fruits using a high capacity absorbent polymer for water

A single extraction and a single clean-up procedure was developed for multi-residue analysis of pesticides in non-fatty vegetables and fruits. The method involves the use of a high capacity absorbent polymer for water as a drying agent in extraction from wet food samples and of a graphitized carbon column for clean-up. A homogeneously chopped food sample (20 g) and polymer (3 g) were mixed to absorb water from the sample and then 10 min later the mixture was vigorously extracted with ethyl acetate (100 ml). The extract (50 ml), separated by filtration, was loaded on a graphitized carbon column without concentration. Additional ethyl acetate (50 ml) was also eluted and both eluates were concentrated to 5 ml for analysis. The procedure for sample preparation was completed within 2 h. In a recovery test, 107 pesticides were spiked and average recoveries were more than 80% from asparagus, orange, potato and strawberry. Most pesticides were recovered in the range 70-120% with usually less than a 10% RSD for six experiments. The results indicated that a single extraction with ethyl acetate in the presence of polymer can be applied to the monitoring of pesticide residues in foods.     

Multiresidue determination of pesticides in juice by solid-phase extraction and gas chromatography-mass spectrometry

A multiresidue method based on solid-phase extraction was developed for the simultaneous determination of 50 pesticides in commercial juices. The extraction procedure was carried out in C₁₈ columns preconditioned with acetonitrile and water. The subsequent elution of pesticides was performed with a mixture of hexane-ethyl acetate (1:1, v/v) prior to the determination by gas chromatography with electron impact mass spectrometric detection in the selected ion monitoring mode (GC-MS-SIM), using one target and two qualifier ions. Standards were prepared spiking blank juice samples to counteract the observed matrix effect. Average recoveries for all the pesticides studied were higher than 91% with relative standard deviations lower than 9% in the concentration range of 0.02-0.1 μg/mL and the detection limits achieved ranged from 0.1 to 4.6 μg/L. The proposed method was applied to the analysis of these compounds in commercial juices and diazinon, ethion and procymidone were the pesticides encountered, although the levels found were very low.     

Multiresidue analysis of pesticides in vegetables and fruits using two-layered column with graphitized carbon and water absorbent polymer

A high-throughput multiresidue analysis of pesticides in non-fatty vegetables and fruits was developed. The method consisted of a single extraction and a single clean-up procedure. Food samples were extracted with ethyl acetate and the mixture of extract and food dregs were poured directly into the clean-up column. The clean-up column consisted of two layers of water-absorbent polymer (upper) and graphitized carbon (lower), which were packed in a reservoir (75 ml ) of a cartridge column. The polymer removed water in the extract while the carbon performed clean-up. In a recovery test, 110 pesticides were spiked and average recoveries were more than 95% from spinach and orange. Most pesticides were recovered in the range 70-115% with RSD usually < 10% for five experiments. The residue analyses were performed by the extraction of 12 pesticides from 13 samples. The two methods resulted in similar residue levels except chlorothalonil in celery, for which the result was lower with the proposed method. The results confirmed that the proposed method could be applied to monitoring of pesticide residue in foods.     

Multiresidue analysis of pesticides in fresh fruits and vegetables using procedures developed by the Florida Department of Agriculture and Consumer Services

Improved quality and efficiency of pesticide residue analysis were achieved by examining all aspects of the laboratory process. In an effort to eliminate methylene chloride hazardous waste, an acetonitrile extraction method, originally developed by the California Department of Agriculture, was modified and adopted. Sample size and solvent consumption were reduced with the new method. Custom glassware racks and disposable supplies reduced overall analysis time. Gravity-fed, solid-phase extraction simplified sample preparation and provided cleaner extracts for gas chromatographic analyses. Modifications to the method were made to achieve the ruggedness needed to maintain quality objectives during routine analysis. Instrumental improvements, including new selective detectors, retention time locking, and mass spectrometry screening for all samples, provided the laboratory with efficient, reliable, and confirmed analytical results.     

A rapid multiresidue method for determination of pesticides in fruits and vegetables by using acetonitrile extraction/partitioning and solid-phase extraction column cleanup

A modification of a rapid and inexpensive multiresidue method for determination of pesticides in fruits and vegetables (QuEChERS method) is presented. Samples were extracted by shaking with acetic acid-acetonitrile (1 + 99). Water was removed by liquid-liquid partitioning with magnesium sulfate and sodium acetate. The extract was subjected to a single solid-phase extraction (SPE) column cleanup, which produced a cleaner extract than did the dispersive SPE cleanup used in the original QuEChERS method. Recovery data were obtained for 316 pesticide residues, at levels ranging from 20 ppb to 1.0 ppm. Data were provided by 3 different laboratories. The modified QuEChERS method resulted in a 65% reduction in solvent usage, when compared with the traditional multiresidue methods previously used in our laboratories.     

A simple and inexpensive "solvent in silicone tube extraction" approach and its evaluation in the gas chromatographic analysis of pesticides in fruits and vegetables

A novel, simple, and inexpensive approach to sorptive extraction, which we call solvent in silicone tube extraction (SiSTEx), was applied to pesticide residue analysis and its effectiveness and efficiency were evaluated. In SiSTEx, which is a form of open tubular sorptive extraction, a piece of silicone tubing (4 cm long, 1.47 mm ID, 1.96 mm OD in this study) is attached to the cap of a 20 mL glass vial that contains the aqueous sample. The tubing is plugged at the end dangling in the sample solution, and MeCN (e.g., 40 microL) added by syringe to the inner tube volume through a septum in the cap. A stir-bar is used to mix the sample for a certain time (e.g., 60 min), which allows chemicals to partition into the tubing where they diffuse across the silicone and partition into the MeCN. The final MeCN extract is then analyzed for the concentrated analytes. In this study, the SiSTEx approach was evaluated for the analysis of organophosphorus (OP) and organochlorine (OC) pesticides in fruits and vegetables using GC/pulsed flame photometric (PFPD) and halogen specific (XSD) detectors for analysis. The produced samples were initially extracted by a rapid MeCN procedure, and 5 mL of the initial extract was diluted four-fold with water to undergo sorptive extraction for 60 min. The final extract was analyzed by GC/PFPD + XSD for 14 OP and 22 OC pesticides. This simple approach was able to detect 26 of the 36 pesticides at 10 ng/g or less original equivalent sample concentration with average reproducibility of 11% RSD. For those 26 pesticides, a 44-fold lower detection limit on average was achieved in matrix extracts using SiSTEx despite the four-fold dilution with water.     

Multiresidue analysis of pesticides in vegetables and fruits by gas chromatography/mass spectrometry after gel permeation chromatography and graphitized carbon column cleanup

A multiresidue method for pesticides that enables quantitative, sequential analysis of a large number of vegetable and fruit samples by gas chromatography/mass spectrometry has been developed. First, 89 important target compounds were selected for monitoring, and then the appropriate internal standards for these pesticides, 14 stable isotopically labeled pesticides (surrogates), were used. The sample was extracted with acetonitrile, and the extract was cleaned up by a salting-out step followed by redissolution in ethyl acetate. Coextractives were removed automatically by gel permeation chromatography with a graphitized carbon column, and then by use of a tandem silica-gel/PSA cartridge column. Recoveries of 82 of the 89 pesticides from fortified spinach, tomato, apple, and strawberry were within a range from 70 to 120%, and the relative standard deviation values of 80 of the 89 pesticides were <5%. The method was applied to 188 commercial vegetable and fruit samples to demonstrate its use in routine analysis.     

Continuous solid-phase extraction and gas chromatographic determination of organophosphorus pesticides in natural and drinking waters

A simple, rapid continuous-flow solid-phase extraction method with gas chromatographic detection for the determination of organophosphorus pesticides is proposed. The continuous system consists of an adsorbent column where pesticides are preconcentrated and subsequently eluted with ethyl acetate. Various sorbent materials were assayed of which RP-C18 was found to provide the best results, with a sorption efficiency close to 100%. A comparative study of the determination of pesticides in aqueous samples was conducted using gas chromatography with nitrogen-phosphorus (NPD) and flame ionization (FID) detection. The detection limits of the method for 10 ml of sample were between 50-130 ng/l and 4.5-1 1.7 microg/l with NPD and FID detection, respectively. The method was used to determine organophosphorus pesticides in river, pond, well and tap waters, all with good precision (2.9-4.3%) and recoveries ranging from 93.8 to 104.5%.     

Multiresidue methods using solid-phase extraction techniques for monitoring priority pesticides, including triazines and degradation products, in ground and surface waters

The review describes the use of solid-phase extraction (SPE) techniques for monitoring priority pesticides in ground and surface waters. The focus is on triazine herbicides and their degradation products. Data concerning the fate, occurrence, properties and extraction of triazines and their degradation products using different SPE techniques are tabulated and discussed.     

Determination of triazine herbicides in fruits and vegetables using dispersive solid-phase extraction coupled with LC-MS

A simple, rapid, and sensitive liquid chromatography-mass spectrometry (LC-MS) method was successfully developed for the determination of three chloro-s-triazine herbicides, viz. atrazine, simazine, and propazine, two thiomethyl-s-triazine ones, viz. ametryn and prometryn, and prometon in fruits and vegetables. The instrumental parameters affecting LC separation and MS detection were investigated and the best conditions were selected. Samples were extracted and purified by dispersive solid-phase extraction (dispersive-SPE) with a primary-secondary amine sorbent. Three typical representative samples (luffa, broad bean, and grape) were selected to investigate the effect of different matrices on pesticide recoveries and assay precision after spiking at 0.05 mg/kg. Matrix composition did not interfere significantly with the determination of these pesticides. The recoveries were, with a few exceptions, in the range of 80-110% with relative standard deviations less than 10% (n = 5). In addition, this method was also applied to 21 different kinds of agriculture products collected from the local market, and two of the six triazines could be detected and quantified.     

Headspace solid-phase microextraction for the gas chromatographic analysis of organophosphorus insecticides in vegetables

Residues of organophosphorus insecticides (diazinon, methyl parathion, fenitrothion, malathion, and parathion) were determined in 13 different vegetable matrixes by headspace solid-phase microextraction performed with a polydimethyl-siloxane fiber (100 microm). Determination was carried out by gas chromatography with a nitrogen-phosphorus detector. Limits of detection and quantification were < 0.005 and 0.017 mg/kg, respectively; thus, the limits of maximum residue levels (MRLs) required by European regulations can be verified without difficulty. Pesticide residues were found in 38% of the 125 fresh commercial samples (imported and domestic) that were analyzed. Residues of methyl parathion and parathion, which were withdrawn in Greece in 2003, were detected in 36.8 and 4% of all samples, respectively. The MRLs were exceeded overall by 1%.     

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。     

Determination of urea-derived pesticides in fruits and vegetables by solid-phase preconcentration and capillary electrophoresis

A multiresidue analytical method based on solid-phase extraction (SPE) enrichment combined with capillary electrophoresis (CE), using micellar electrokinetic capillary chromatography (MEKC), was developed to determine ten substituted urea pesticides in orange and tomato samples. Several factors such as pH, composition and concentration of the buffer, concentration of surfactant, addition of organic solvent, and working voltage were optimized to obtain the best compound separation in the shortest time. Separation can be achieved in 7 min using a micellar aqueous pH 9 buffer composed of 4 mM borate and 35 mM sodium dodecyl sulfate. After an SPE procedure, which provided a 10-fold enrichment, the limit of detection was about 0.05 mg kg(-1), which is in the order of the maximum residue limits (MRLs) established by the European Union (EU) for most of these compounds. Increasing the enrichment factor by using a larger amount of sample is difficult in oranges due to the matrix interferences, but is possible in tomatoes, which gave cleaner extracts and easily reached a 25-fold enrichment factor. The procedure involving SPE and CE provided acceptable recoveries (ranged 42-118%) and relative standard deviations (RSDs; < 19%) at levels between 0.3 and 5 mg kg(-1).     

Application of gas chromatography-tandem mass spectrometry to the analysis of pesticides in fruits and vegetables

A new analytical method was devised using gas chromatography with tandem mass spectrometry (GC-MS-MS) for the routine analysis of 31 multi-class pesticide residues and approximately 8000 fresh fruit and vegetable samples (green bean, cucumber, pepper, tomato, eggplant, watermelon, melon, and marrow). Extraction of the pesticides with dichloromethane was carried out. The optimal ionization mode, either electron impact or chemical ionization, was selected for each pesticide in the same run. Carbofrit was used in the liner and combined with the selectivity of the detector this avoided additional clean-up. Thus, not only was money and time saved, the uncertainty of the method was decreased in its application to routine analysis. The average recoveries in cucumber obtained for each pesticide ranged between 71 and 119% at two different fortification levels (n=10 each) that ranged between 7 and 300 ng g(-1) (depending on the pesticide). The relative standard deviation was lower than 19% for all compounds tested. The calculated limits of detection and quantification were typically <1 ng g(-1) which were much lower than the maximum residue levels established by European legislations.     

Multiresidue analysis of 74 pesticides in fruits and vegetables by liquid chromatography–electrospray–tandem mass spectrometry

A multiresidue method is described for the determination of 74 pesticides commonly used in crop protection including mainly carbamate, conazole, benzimidazole and pyrimidine fungicides and insecticides. Pesticides residues are extracted from the samples with ethyl acetate. No additional clean-up steps are necessary. Analysis is performed by liquid chromatography–electrospray ionization–tandem mass spectrometry. The method has been validated for various fruits and vegetables matrices. Good sensitivity and selectivity of the method are obtained with limits of quantification of 0.01 mg/kg in almost all cases. Recoveries, RSD and accuracy values of the method fulfilled the criteria of validation commonly admitted. The method was applied very satisfactorily to routine analysis as a complement to traditional GC method. More than 2500 fruits and vegetables samples have been controlled, as a part of the pesticide monitoring program of the “Service de Protection de la Consommation” in Geneva. Quality control systems applied during the assays have demonstrated very good performances and stability with time.     

New materials for solid-phase extraction and multiclass high-performance liquid chromatographic analysis of pesticides in grapes

Sample preparation procedures which included the use of new aminopropyl (NH2) and octadecyl (C18) solid-phase extraction (SPE) sorbents are proposed for the simultaneous multiclass determination of the fungicide benomyl and of the herbicides tebuthiuron, diuron, simazine, atrazine, and ametryn in grapes, using single wavelength high-performance liquid chromatography. Sorbent preparation uses a fast, easy, and effective procedure to obtain silica-based materials, made by depositing polysiloxanes on a silica support followed by thermal immobilization. Recovery results of the compounds, after elution from the SPE cartridges, indicate that the most efficient system employed silica loaded with 40% of an aminofunctional polydimethylsiloxane as sorbent, using dichloromethane:methanol (95:5, v/v) as eluent. Method validation, carried out in agreement with International Conference on Harmonization directives, was performed at three fortification levels (100, 200, and 1000 microg kg(-1)). Limits of detection and quantification show that the method developed can be used to detect the pesticides at concentrations below the maximum residue levels established by Codex Alimentarius, the US Environmental Protection Agency, the European Union, and Brazilian legislation.