QuEChERS Technique for the Gas Chromatographic Determination of Organophosphate Residues in Strawberries

This study describes the validation of an analytical method employing gas chromatography with flame photometric detection for the determination of organophosphate pesticides (diazinon, disulfoton, parathion, chlorpyrifos, and malathion) in strawberries. The method employed a QuEChERS dispersive solid phase extraction for the sample preparation. QuEchERS is inexpensive, fast, and easy for the separation of the analytes from the matrix. In addition, the method provided linear calibration curves, ranging from 0.10–1.00 µg g^?1, for diazinon, disulfoton, parathion, and chlorpyrifos, and 0.10–2.00 µg g^?1 for malathion. Recovery studies yielded values in the range from 81.64 to 100.00%. These results demonstrated the potential of the technique for the determination of organophosphate residues in strawberries.     

Multiresidue Method for the Determination of Organophosphorus Pesticides in Still Wine and Fortified Wine Using Solid-Phase Microextraction and Gas Chromatography – Tandem Mass Spectrometry

A SPME-GC-MS/MS method for the determination of eight organophosphorus pesticides (azinphos-methyl, chlorpyriphos, chlorpyriphos-methyl, diazinon, fenitrothion, fenthion, malathion, and methidathion) in still and fortified wine was developed. The extraction procedure is simple, solvent free, and without any sample pretreatment. Limits of detection (LOD) and quantitation (LOQ) values in the range 0.1–14.3 µg/L and 0.2–43.3 µg/L, respectively, were obtained. The LOQ values are below the maximum residue levels (MRLs) established by European Regulation for grapes, with the exception of methidathion. Coefficients of correlation (R²) higher than 0.99 were obtained for the majority of the pesticides, in all different wines analyzed.     

Application of a single-drop microextraction for the analysis of organophosphorus pesticides in juice

In this study, a new method for the determination of organophosphorus pesticides (OPPs) (ethoprophos, diazinon, parathion methyl, fenitrothion, malathion, isocarbophos and quinaphos) in orange juice was developed. Single-drop microextraction (SDME) parameters, such as organic solvent, drop volume, agitation rate, extraction time, and salt concentration were optimized through analysis of OPPs in fortified water. The orange juice was simply centrifuged and diluted with water, extracted by SDME and analyzed by gas chromatography (GC) equipped with a flame photometric detection (FPD). Fortification tests were conducted for concentrations between 10 and 500 microg/L; mean relative recoveries for each pesticide were all above 76.2% and below 108.0%. Limits of detection of the method for orange juice were below 5 microg/L for all target pesticides. The repeatability of the proposed method, expressed as relative standard deviation varied between 4.6 and 14.1% (n=5). The proposed method is acceptable in the analysis of OPPs pesticides in juice matrices.     

Application of the molecularly imprinted solid-phase extraction to the organophosphate residues determination in strawberries

This study describe an analytical method employing gas chromatography (GC) using flame photometric detection that has been developed for the simultaneous determination of organophosphate pesticides (diazinon, disulfoton, parathion, chlorpyrifos and malathion) in strawberry samples. For this purpose, molecularly imprinted solid-phase extraction was applied as a sample preparation technique. The method was linear in the ranges from 0.10 to 1.00?μg?g^?1, for diazinon, disulfoton, parathion and chlorpyrifos, and 0.10 to 2.00?μg?g^?1 for malathion with r?>?0.99. The detection limits (LD) ranged from 0.02 to 0.05?μg?g^?1. Recovery studies yielded average recoveries in the range of 65.25 to 87.70?%. These results showed the potential of this technique for organophosphate residue monitoring in strawberry samples.     

分散液液微萃取-气相色谱法快速测定水中23种有机磷农药

建立了分散液液微萃取(DLLME)的新型样品前处理方法,并采用气相色谱/火焰光度检测器对饮用水中的治螟磷、甲拌磷、二嗪农、乙拌磷、甲基毒死蜱、甲基对硫磷、皮蝇磷、杀螟松、马拉硫磷、毒死蜱、倍硫磷、对硫磷、溴硫磷、嘧啶磷、甲基异硫磷、稻丰散、杀扑磷、丙溴磷、乙硫磷、三唑磷、三硫磷、哒嗪硫磷、亚胺硫磷23种痕量有机磷农药残...     

固相微萃取/气相色谱-质谱检测纺织品中有机磷农药残留

采用PDMS萃取纤维一次吸附富集纺织品中马拉硫磷、甲基对硫磷、敌敌畏、三唑磷、对硫磷、喹硫磷、二嗪磷7种有机磷农药,在气相色谱-质谱(GC-MS)进样口热解吸后进行定性定量检测。筛选了几种商品化的萃取纤维,并优化了萃取时间、萃取温度、吸附时间、盐浓度以及pH值等萃取条件。本方法操作简单、快速、环保,检出限低,可适用于生态纺织品中物质的快速检测。     

Rapid clean-up of fat extracts for organophosphorus pesticide residue determination using C18 solid-phase extraction cartridges

Commercial solid-phase extraction (SPE) cartridges with C₁₈ bonded silica packings effectively cleaned up acetonitrile extracts of 3-g samples of fats and oils for determination of organophosphorus pesticide residues by gas chromatography with flame photometric detection. Cartridges from three different sources were tested and found to differ in lipid capacity and inertness (free silanol activity). Consequently, the amount of packing (i.e., number of cartridges) and/or the choice of eluent used were adjusted for each brand of cartridge to achieve optimum clean-up and analyte recovery. Seven pesticides with a wide range of polarity (acephate, azodrin, chlorpyrifos, diazinon, malathion, methamidophos and methyl parathion) were separated from coextracted lipids by elution with either acetonitrile or methanol, depending on the brand of cartridge used. Cartridges were regenerated by purging lipids with dichloromethane and were reused numerous times without apparent loss of effectiveness. Recoveries from vegetable oils and butterfat fortified with the seven compounds at levels of 0.05–0.87 μg g^?1 ranged from 80 to 103%. Practical limits of determination range from 0.01 to 0.08 μg g^?1, depending on analyte response.     

Confirmation of chlorotriazine pesticides,their degradation products and organophosphorus pesticides in soil samples using gas chromatography-mass spectrometry with electron impact and positive- and negative-ion chemical ionization

Gas chromatography-mass spectrometry (GC-MS) with electron impact (EI), positive-ion chemical ionization (PCI) and negative-ion chemical ionization (NCI) were applied as confirmatory techniques for residue analysis of chlorotriazine pesticides, their degradation products and organophosphorus pesticides in soil samples. Clean-up was effected using a Florisil column with subsequent analysis by GC with a nitrogen-phosphorus detector. GC-MS with the EI mode of operation is the common mode of confirmation for all the pesticides. Further confirmation by either GC-MS with PCI and NCI for chlorotriazines and organophosphorus pesticides, respectively, is recommended. The method was applied to the determination of residue levels of atrazine, deethylatrazine, deisopropylatrazine, simazine, fenitrothion and tetrachlorvinphos in several soil samples at levels from 5 ng g^?1 to 9 μg g^?1.     

Evaluation of a modified QuEChERS method for the extraction of pesticides from agricultural, ornamental and forestal soils

A modified version of the QuEChERS method has been developed for the determination of a group of ten organophosphorus pesticides (i.e. ethoprofos, dimethoate, diazinon, malaoxon, chlorpyrifos-methyl, fenitrothion, malathion, chlorpyrifos, fenamiphos and phosmet) and one thiadiazine pesticide (buprofezin) in three different types of soils (forestal, ornamental and agricultural). The method was validated through linearity, recovery, precision and accuracy studies, and also by carrying out a matrix-matched calibration for the three soils owing to the existence of a strong matrix effect. Acceptable recovery values were obtained (between 45 and 96%) for all the pesticides and soils, except for malathion and malaoxon in forestal and ornamental soils, from which they could not be quantitatively extracted. Limits of detection of the whole method ranged between 0.48 and 7.78 ng/g. The method was finally applied to the determination of chlorpyrifos concentration in a treated soil for cultivation of potatoes.     

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%.     

Adsorption of diazinon and fenitothion on MCM-41 and MCM-48 mesoporous silicas from non-polar solvent

The adsorption of two common organophosphorus pesticides, diethoxy-[(2-isopropyl-6-methyl-4-pyrimidinyl)oxy]-thioxophosphorane (diazinon) and dimethoxy-(3-methyl-4-nitrophenoxy)-thioxophosphorane (fenitrothion), by MCM-41 and MCM-48 mesoporous silicas at room temperature was investigated. UVvis and IR spectroscopy, small-angle X-ray diffraction, and the specific surface area analysis (S _BET) were used to study the adsorption behavior of diazinon and fenitrothion. The results show that the MCM-41 and MCM-48 mesoporous silicas adsorb diazinon more efficiently than fenitrothion. The extraction of adsorbed materials from the adsorbents with polar solvents and subsequent analysis by ³¹P NMR showed that the adsorption of diazinon and fenitrothion on mesoporous silicas is destructive and non-destructive, respectively. Nitrogen adsorption measurements showed that the specific surface area of both silicas decreases after the adsorption of pesticides, and the larger effect is observed for diazinon. The article is published in the original.     

Determination of organophosphorus pesticide residues in fruits by gas chromatography with ITD and NPD detection

Summary Several widely used organophosphorus insecticides, diazinon, methyl-parathion, fenitrothion, malathion, fenthion and methidathion were selected for inclusion in this work. A comparative study of the multiresidue determination of these compounds in citrus fruit and grapes has been carried out by gas chromatography with nitrogen-phosphorus and ion trap detection. Samples were spiked with 0.1, 0.5 and 1 mg kg^–1 of each pesticide and blended in a Sorvall homogeniser with ethyl acetate. Column clean-up on Florisil was necessary for citrus peel extracts. The average recoveries varied from 81 to 107% with a relative standard deviation between 0.3 and 9.5% for GC-ITD and from 86 to 104% with a relative standard deviation ranging from 1.4 to 8.0% for GC-NPD. The detection limit of the method was 10 ng g^–1 or less for each organophosphorus insecticide, with both detectors. This method was applied to the analysis of treated lemons and 0.25 mg kg^–1 of fenitrothion in fruit was detected a week after treatment and identified by its mass spectrum. The results obtained showed that the proposed methods are reproducible and sensitive enough for the simultaneous determination of these insecticides in fruits at residue level.     

Extraction of pesticides from aqueous samples: A comparative study

Three different extraction procedures for eight pesticides (chlorfenvinphos, diazinon, ethyl parathion, ethiofencarb, fenitrothion, malathion, metalaxyl, pirimicarb) in water samples are compared. The extraction procedures are: liquid-liquid extraction (LLE), solid-phase extraction (SPE) and microextraction (ME). For each procedure the most suitable conditions were obtained experimentally, with special remarks on ME, in which the effects of different mixtures of Kaltron with other solvents were tested. A preconcentration factor (PF) was used to rank the methods; the best results were observed for ME, (PF 15–45, whereas PF < 10 for SPE, and PF 13 for LLE). In all cases, the determination was performed by gas chromatography, using a nitrogen phosphorus detector and the internal standard method (methyl parathion) as the quantification procedure.     

Immunochemical determination of four organophosphorus insecticide residues in olive oil using a rapid extraction process

Sensitive, simple and rapid ELISA methods have been developed for the determination of four organophosphorus pesticides in extra virgin olive oil. The analytical procedure involves simultaneous extraction of the analytes from oil matrix with methanol and a freezing clean-up step (−80 °C), followed by immunoassay determination using standards in matrix. The methodology is specific for diazinon, fenthion, malathion and chlorpyrifos showing little or no cross-reactivity against other organophosphorus compounds. Limits of detection for the pesticides in olive oil are from 46 ng ml⁻¹ for diazinon to 10 ng ml⁻¹ for fenthion, all of them under the established MRLs for olives. The excellent recoveries (between 94 and 122%) obtained by the complete analytical protocol confirm the potential of this approach for detecting these compounds in olive oil, being useful as screening and complementary method in pesticide regulatory and food safety programs. The proposed methodology also correlates well with the reference chromatographic (GC-MS) methods.     

Rapid multiresidue screening method for organophosphate pesticides in vegetables

Summary A rapid and efficient multiresidue extraction procedure using ethyl acetate and sodium sulfate has been applied to the analysis of diazinon, methamidophos, chlorpyrifos, malathion, parathion, parathion-methyl, dimethoate and monocrotophos residues in many different kinds of vegetables. No cleanup step was required Concentrated extracts were analysed by gas chromatography with flame photometric detection in phosphorus mode. Recovery studies were performed in six kinds of matrices at two fortification levels. Recoveries were in the range 80–115%. The limit of quantification of the analytical method has been estimated as 0.01 ppm for diazinon, methamidophos and malathion, 0.03 ppm for chlorpyrifos, parathion, parathion-methyl and dimethoate and 0.1 ppm for monocrotophos. Experiments showed that potentially it should be possible to develop a rapid and universally applicable method for organophosphate pesticide residues in different matrices.     

Synthesis of three haptens for the class-specific immunoassay of O,O-dimethyl organophosphorus pesticides and effect of hapten heterology on immunoassay sensitivity

A general and broad class-specific enzyme-linked immunosorbent assay was developed for the O,O-dimethyl organophosphorus pesticides, including malathion, dimethoate, phenthoate, phosmet, methidathion, fenitrothion, methyl parathion and fenthion. Three haptens with different spacer-arms were synthesized. The haptens were conjugated to bovine serum albumin (BSA) for immunogens and to ovalbumin (OVA) for coating antigens. Rabbits were immunized with the immunogens and six polyclonal antisera were produced and screened against each of the coating antigens using competitive indirect enzyme-linked immunosorbent assay for selecting the proper antiserum. The effect of hapten heterology on immunoassay sensitivity was also studied. The antibody-antigen combination with the most selectivity for malathion was further optimized and tested for tolerance to co-solvent, pH and ionic strength changes. The IC₅₀ values, under optimum conditions, were estimated to be 30.1 μg L⁻¹for malathion, 28.9 μg L⁻¹ for dimethoate, 88.3 μg L⁻¹ for phenthoate, 159.7 μg L⁻¹ for phosmet, 191.7 μg L⁻¹ for methidathion, 324.0 μg L⁻¹ for fenitrothion, 483.9 μg L⁻¹ for methyl parathion, and 788.9 μg L⁻¹ for fenthion. Recoveries of malathion, dimethoate, phenthoate, phosmet and methidathion from fortified Chinese cabbage samples ranged between 77.1% and 104.7%. This assay can be used in monitoring studies for the multi-residue determination of O,O-dimethyl organophosphorus pesticides.     

气相色谱-火焰光度法测定土壤中有机磷农药残留

建立了气相色谱-火焰光度(GC-FPD)分析土壤中敌敌畏、氧化乐果、二嗪农、乐果、甲基对硫磷、马拉硫磷、对硫磷、水胺硫磷、喹硫磷等9种有机磷农药残留量的方法。样品用丙酮-二氯甲烷(1:3)提取,浓缩、定容后用Hp-5MS(30m×0.25 mm×0.25μm)毛细管柱分离,FPD检测器检测。方法回收率在68.71%～110.39%之间;RSD在5.5%～11%之间;检出限在0.397～1.60μg/mL之间,方法可用于环境土壤样品中有机磷农药残留的测定。     

固相萃取-液相色谱-串联质谱法测定蔬菜中4种有机磷农药及其代谢产物

在蔬菜种植中经常使用的有机磷农药马拉硫磷、甲基对硫磷、敌百虫及乙酰甲胺磷可能转化的主要代谢产物分别为O,O-二甲基二硫代磷酸酯、对硝基酚、敌敌畏及甲胺磷。根据蔬菜色素等基质的含量不同采用不同的净化方法,色素含量高的蔬菜采用活性炭和弗罗里硅土串联固相萃取小柱净化,其他蔬菜采用弗罗里硅土固相萃取小柱净化。色谱分离选择ACQUITY UPLC BEH HILIC色谱柱,以乙腈和5 mmol/L乙酸铵水溶液为流动相进行梯度洗脱,得到的分离效果较好;质谱采用电喷雾正或负离子电离、多反应监测模式检测。液相色谱-质谱检测的基质效应为15.3%~45.1%;4种有机磷农药及其代谢物的方法回收率为76.9%~102.8%,相对标准偏差为5.92%~10.19%;定量限范围为0.001~0.01 mg/L;在0.01~1.00 mg/L范围内线性相关系数为0.9982~0.9999。方法具有良好的回收率、相对标准偏差、定量限及线性关系,适合蔬菜中有机磷及代谢物的检测,应用该检测方法对农贸市场购买的白菜、辣椒、西红柿及洋葱进行了检测。     

Adsorption of diazinon and fenitrothion on nanocrystalline alumina from non-polar solvent

Nanocrystalline ??-alumina was prepared by the sol-gel method from aluminum sec-butoxide and, after characterization by X-ray diffraction and transmission electron microscopy, was used as an adsorbent for two common organophosphorus pesticides, diethoxy-[(2-isopropyl-6-methyl-4-pyrimidinyl)oxy]-thioxophosphorane (diazinon) and dimethoxy-(3-methyl-4-nitrophenoxy)-thioxophosphorane (fenitrothion). Absorption of these pesticides from hexane was monitored by UV-vis and ³¹P NMR spectroscopies. Adsorption of the aforementioned pesticides by nanocrystalline alumina prepared by the sol-gel method and calcined at 500°C and 800°C was compared with their adsorption by micron-size commercial alumina. Sol-gel derived nanocrystalline alumina showed significantly higher activity than commercial alumina in the destructive adsorption of diazinon and fenitrothion. The bonding mode of pesticides over nanocrystalline and commercial ??-aluminas was investigated by infrared spectroscopy.     

Response surface methodology for the microwave-assisted extraction of insecticides from soil samples

The extraction of two pyrethroid insecticides (deltamethrin and α-cypermethrin) together with three organophosphorus insecticides (dimethoate, diazinon and malathion) from soil samples was carried out with microwave-assisted technology. Experimental designs showed that extraction temperature, addition of water to the extractant and solvent/soil ratio were the variables that affected the recoveries of the pesticide the most. Response surface methodology was applied to find the optimum values of the variables involved in the extractions of the analytes. In addition, in order to achieve near-optimal extraction conditions, a desirability function was used to optimize the five pesticides simultaneously. The optimized conditions were applied to different types of soils.