Simple analytical method for organophosphorus pesticide determination in unpolished rice, using removal of fats by zinc acetate

A rapid and simple method is developed for the determination of organophosphorus pesticides in unpolished rice. The new method incorporated acetonitrile-water (1 + 1) extraction, removal of fats by zinc acetate, and further cleanup on an activated charcoal chromatographic column. The higher fatty acids in the extract react rapidly with zinc acetate to form insoluble zinc carboxylates, which precipitate. Additional interferences were cleaned up on an activated charcoal chromatographic column, and organophosphorus pesticides adsorbed on the activated charcoal were eluted with acetone-hexane. Dimethoate is not retained on the activated charcoal and must be extracted with dichloromethane from the first acetonitrile-water eluate. Pesticides are measured by flame photometric gas chromatography. Recoveries from 50 g unpolished rice samples fortified with 5-50 micrograms diazinon, 6-30 micrograms parathion, 8-40 micrograms fenitrothion and IBP, 10-50 micrograms dimethoate and fenthoate, 20-100 micrograms malathion, or 40-200 micrograms EPN ranged from 75.7 to 95.8%.     

Assessment of pesticide residues in honey samples from portugal and Spain

Fifty samples of honey collected from local markets of Portugal and Spain during year 2002 were analyzed for 42 organochlorine, carbamate, and organophosphorus pesticide residues. An analytical procedure based on solid-phase extraction with octadecyl sorbent followed by gas chromatography-mass spectrometry (GC-MS), for organochlorines, and by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS), for organophosphorus and carbamates, has been developed. Recoveries of spiked samples ranged from 73 to 98%, except for dimethoate (40%), with relative standard deviations from 3 to16% in terms of repeatability, and from 6 to 19% in terms of reproducibility. Limits of quantification were from 0.003 to 0.1 mg kg(-)(1). Most of the pesticides found in honey were organochlorines. Among them, gamma-HCH was the most frequently detected in 50% of the samples, followed by HCB in 32% of the samples and the other isomers of HCH (alpha-HCH and beta-HCH) in 28 and 26% of the samples, respectively. Residues of DDT and their metabolites were detected in 20% of the samples. Of the studied carbamates, both methiocarb and carbofuran were detected in 10% of the samples, pirimicarb in 4% and carbaryl in 2%. The only organophosphorus pesticides found were heptenophos in 16%, methidathion in 4%, and parathion methyl in 2% of honey samples. Results indicate that Portuguese honeys were more contaminated than Spanish ones. However, honey consumers of both countries should not be concerned about the amounts of pesticide residues found in honeys available on the market.     

Semiautomated determination of pesticides in water using solid phase extraction disks and gas chromatography-mass spectrometry

A method based on semiautomated solid phase extraction using octadecyl-bonded silica disks and gas chromatography-mass spectrometry, operated in selected ion monitoring mode, allows detection and quantification of approximately 100 pesticides and transformation products in drinking water. Samples (500 mL) were passed through the disk, and the retained pesticides were eluted with acetone and ethyl acetate. Typical recoveries for pesticides at 0.1 microg L(-1) in water were in the range of 72-120% with relative standard deviations less than 20%. Calibration curves were linear over the range of 0.025-0.5 microg mL(-1) (equivalent to a concentration range in drinking water of 0.05-1.0 microg L(-1)).     

Extraction and cleanup procedures for determination of diarylphosphates in fish, sediment, and water samples

Methods for determination of triaryl/alkylphosphates (TAPs) in water, fish, and sediment have been extended to determination of the diarylphosphate (DAP) degradation products. DAPs were extracted from water (adjusted to pH 0.5) by use of XAD-2 resin and determined by gas-liquid chromatography as butyl esters. Recovery of diphenylphosphate (DPP) and o-, m-, p-dicresylphosphates (DoCP, DmCP, DpCP) were greater than 95% in water samples fortified at 1, 10, and 50 micrograms/L. DAPs were extracted from fish with methanol and the extracts were cleaned up on reverse phase (C18) silica cartridges. Recoveries were greater than 87% for DPP, DoCP, DmCP, and DpCP in fish muscle fortified at 50, 100, and 500 ng/g. Sediments were refluxed with aqueous methanol and DAPs were recovered by use of XAD-2 resin. Recoveries of DAPs from sediments fortified at 50 and 100 ng/g were greater than 76%. Interferences (1-10 ng/g) from phosphorus or nitrogen-containing GLC peaks prevented sub- ng/g level analysis for DAPs in sediment and fish extracts.     

Analysis of organophosphorus pesticides in honeybee by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry

Pesticides applied in extended agricultural fields may be controlled by means of bioindicators, such as honeybees, in which are the pesticides bioaccumulate. Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) experiments with positive (PI) and negative (NI) ion modes were optimized for the analysis of 22 organophosphorus pesticides in honeybee samples. The extraction required 3 g of sample, which was extracted with acetone. The extract was purified with coagulating solution and reextracted with Cl(2)CH(2). Pesticides studied could be detected by both ionization modes except for parathion, parathion-methyl, and bromophos, which did not give signals in PI mode, and triazophos, which was not detected in NI mode. Fragmentation voltage and vaporizer temperature were optimized to achieve the highest sensitivity. The spectra profile of each pesticide in PI mode showed the [M + H](+) ion as the main signal, whereas in NI mode only fragment ions were shown. The detection limit obtained in selected ion monitoring mode ranged from 1 to 15 microg kg(-1). The average recoveries from spiked honeybees at various concentration levels (0.5-5 mg kg(-1)) exceeded 65% with relative standard deviations of 4-15%. The method was applied to real samples, in which residues of coumaphos and dimethoate were detected.     

Development of a solid-phase extraction coupling chemiluminescent enzyme immunoassay for determination of organophosphorus pesticides in environmental water samples

Solid-phase extraction (SPE) and direct competitive chemiluminescence enzyme immunoassay (dcCL-EIA) were combined for the detection of organophosphorus pesticides (OPs) in environmental water samples. dcCL-EIA based on horseradish peroxidase labeled with a broad-specificity monoclonal antibody against OPs was developed, and the effects of several physicochemical parameters on dcCL-EIA performance were studied. SPE was used for the pretreatment of water samples to remove interfering substances and to concentrate the OP analytes. The coupling of SPE and dcCL-EIA can detect seven OPs (parathion, coumaphos, phoxim, quinalphos, triazophos, dichlofenthion, and azinphos-ethyl) with the limit of quantitation below 0.1 ng/mL. The recoveries of OPs from spiked water samples ranged from 62.5% to 131.7% by SPE-dcCL-EIA and 69.5% to 112.3% by SPE-HPLC-MS/MS. The screening of OP residues in real-world environmental water samples by the developed SPE-dcCL-EIA and their confirmatory analysis using SPE-HPLC-MS/MS demonstrated that the assay is ideally suited as a monitoring method for OP residues prior to chromatographic analysis.     

Gas chromatographic relative retention data for pesticides on nine packed columns: II. Organophosphorus and organochlorine pesticides, using electron-capture detection

The retention time relative to parathion, absolute retention time, concentration range, peak asymmetry factor, and peak shape class are given for each of 42 organophosphorus pesticides and 28 organochlorine pesticides analyzed by gas chromatography (GC) on 9 different packed columns. The packing materials used were 3% SP-2100, 1% Dexsil-300, 3% OV-17, 1.5% OV-17 + 1.95% QF-1, 4% SE-30 + 6% QF-1, 3% OV-17 + 3% OV-210, 5% DC-200 + 7.5% QF-1,3% Carbowax-20M, and 4% Reoplex-400. Retention data were determined at 200 degrees C with a carrier gas flow at uopt, using a 63Ni electron-capture detector. Results should be useful for preliminary identification of environmental samples and also for single or multiple pesticide residue analysis.     

Simplified cleanup and gas chromatographic determination of organophosphorus pesticides in crops

A simple and efficient cleanup method for gas chromatographic determination of 23 organophosphorus pesticides in crops including onion is described. The sample was extracted with acetone. The extract was purified with coagulating solution, which contained ammonium chloride and phosphoric acid, and then filtered by suction. The filtrate was diluted with NaCl solution and reextracted with benzene. The organic layer was evaporated and injected into a gas chromatograph equipped with a flame photometric detector (FPD) and fused silica capillary columns (0.53 mm id) coated with silicone equivalent to OV-1701, OV-1, and SE-52. Onion extract, which contained FPD interferences, was cleaned up on a disposable silica cartridge. Recoveries of most organophosphorus pesticides from spiked crops: mandarin orange, tomato, spinach, sweet pepper, broccoli, lettuce, and onion at levels of 0.02-0.28 ppm, exceeded 80%, but the water-soluble pesticides dichlorvos and dimethoate gave poor recoveries in all crops; the nonpolar pesticides disulfoton, chlorpyrifos, fenthion, prothiophos, and leptophos were not recovered quantitatively in spinach, sweet pepper, broccoli, and lettuce. IBP, edifenphos, phosmet, and pyridaphenthion were not recovered from onion because of adsorption to the silica cartridge. The detection limits ranged from 1.25 to 17.5 ppb on a crop basis.     

Quantitative determination of pyrethroids, pyrethrins, and piperonyl butoxide in surface water by high-resolution gas chromatography/high-resolution mass spectrometry

A new method for determination of pyrethroids, pyrethrins, and piperonyl butoxide (PBO) by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) was developed for surface water samples. The method is based on sampling 100 L of ambient surface water with a solid phase extraction (SPE) technique that uses both wound glass fiber filters for collecting the particulate-associated chemicals and XAD-2 resin for collecting the dissolved chemicals. The method detection limits of the analytes ranged from 0.58 to 8.16 ng/sample, which is equivalent to a detection limit range of 0.0058-0.082 ng/L for a 100 L water sample collected by the SPE technique. The SPE when coupled with HRGC/HRMS was a suitable match for detecting these chemicals at subnanogram per liter ranges that are toxicologically significant to aquatic organisms. To confirm the utility of this method for environmental applications, pyrethroids and PBO were found at subnanogram per liter concentrations in surface water samples collected from five tributaries (primarily urban creeks) of the San Francisco Bay, California.     

Determination of Acidic Pesticides in the Drinking Water of Greece Using Capillary Gas Chromatography-Mass Spectrometry

There is no data currently available on acidic pesticides in the drinking water of Greece, although considerable quantities of them are in use. In this study, the occurrence of the six most important acidic herbicides in the drinking water of Greece was investigated. The target compounds studied include four chlorophenoxy herbicides, namely mecoprop, dichlorprop, MCPA and 2,4-D, and two other acidic herbicides, i.e. bromoxynil and bentazone. Analysis was carried out at a concentration level of 100 ng L^?1 using capillary gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring (SIM). The method involved a pre-concentration with solid phase extraction and derivatization with pentafluorobenzyl bromide. Thirty-eight samples of drinking water from nine regions in Greece were screened. No herbicides were detected although fortification experiments with parallel water samples resulted in recovery rates better than 70%. The detection limits of the recovered compounds were found to be between 10 and 50 ng L^?1.     

SBSE-GC-ECD/FPD in the analysis of pesticide residues in Passiflora alata Dryander herbal teas

Stir bar sorptive extraction (SBSE) in combination with GC-ECD/FPD analysis is here applied to the determination of the residues of 11 pesticides (hexachlorobenzene, lindane, chlorothalonil, parathion methyl, parathion ethyl, fenitrothion, malathion, dieldrin, alpha- and beta-endosulfan, and tetradifon) in herbal teas prepared with Passiflora alata Dryander spiked leaves. The method was optimized using spiked herbal teas in a range from 0.05 to 1 pg/microL for organochlorine pesticides and from 0.15 to 3 pg/microL for organophosphorus pesticides. The method is reproducible and repeatable with recoveries calculated from herbal teas prepared with spiked plant material versus spiked herbal teas, varying from about 30% for tetradifon to about 90% for parathion methyl and malathion. The limits of quantitation (LOQs) ranged from 0.017 pg/microL for lindane to 0.117 pg/microL for malathion.     

Direct determination of p-nitrophenyl substituent organophosphorus nerve agents using a recombinant Pseudomonas putida JS444-modified Clark oxygen electrode

A microbial biosensor for rapid, sensitive, selective, and cost-effective determination of the total content of organophosphorus nerve agents with p-nitrophenyl substituent is reported. The biosensor consisted of genetically engineered PNP-degrader Pseudomonas putida JS444 expressing organophosphorus hydrolase (OPH) on its cell surface immobilized on a dissolved oxygen electrode. Surface-expressed OPH catalyzed the hydrolysis of organophosphorus pesticides with p-nitrophenyl substituent such as paraoxon, methyl parathion, and parathion to release p-nitrophenol that was oxidized by the enzymatic machinery of Pseudomonas putida JS444 to carbon dioxide while consuming oxygen. The oxygen consumption was measured and correlated to the concentration of organophosphates. The sensor signal and response time were optimized with 0.086 mg dry weight of cell and operating in 50 mM pH 7.5 citrate-phosphate buffer with 50 microM CoCl(2) at room temperature. When operated at optimized conditions, the biosensor measured as low as 55 ppb of paraoxon, 53 ppb of methyl parathion, and 58 ppb of parathion without interference from most phenolic compounds and other commonly used pesticides, such as atrazine, coumaphos, sutan, sevin, and diazinon. The operational life of the microbial biosensor was approximately 5 days when stored in the operating buffer at 4 degrees C.     

设施大棚农药污染残留调查分析

利用弗罗里矽柱净化前处理方法,采用气相色谱（GC）方式,依据保留时间和特征离子丰度比,对辽宁某地区大棚内种植黄瓜及其叶片部分样品中的有机磷类农药（粉锈宁、乐果、敌敌畏、喹硫磷、辛硫磷、噻嗪酮、甲拌磷、马拉硫磷和对硫磷）,拟除虫菊酯类农药（百菌清、氯氰菊酯、氰戊菊酯、溴氰菊酯）的残留量进行检测分析。结果表明,有机磷类农药检出种类不固定,拟除虫菊酯类农药检出情况较为稳定,有机磷和拟除虫菊酯类农药在叶片中的检出率均略高于在果实中的检出率,且在不同时期不同大棚检出情况略有差异。针对当前农药施用现状,应多注意有机磷类和拟除虫菊酯类农药的使用和监管,对于有机磷类高毒性农药应减少或停止施用,中低毒性的拟除虫菊酯类农药应加强其作用的宣传并控制其使用量,避免追求高产量而盲目过量的施用,造成不必要的污染。     

Determination of halogenated phenols in raw and potable water by selected ion gas chromatography-mass spectrometry

Pentafluorobenzylation and in situ acetylation are compared in the determination of phenol and halogenated phenols in water samples. The latter technique is considered superior to the former for determining phenols at the ng/L level because of less background interference and better recoveries (80% or better except for pentachlorophenol and trichloroguaiacol which had recoveries of about 60%). Further evaluation of the in situ technique by electron capture gas chromatography and gas chromatography-mass spectrometry shows that the latter, in the selected ion monitoring mode, is more suitable because, unlike GC-ECD, it can confirm and quantitate all phenols. In particular, GC-ECD could not detect even high levels of phenol and the monohalogenated phenols. Phenols at 5-473 ng/L were detected in some Canadian drinking water supplies by the in situ acetylation technique combined with GC-MS.     

基于构建微生物传感器的甲基对硫磷降解菌的分离鉴定及其降解特性研究

有机磷农药是目前环境中残留量最多的农药之一,对其残留量的检测及降解机制的研究对于环境污染及生态修复具有重要意义。微生物传感器由生物学元件与换能器构成,因具有成本低廉、易于微型化及选择性高等特点而被广泛应用于各种生化物质的分析和检测。本文从长期受农药污染的土壤中分离出4株能以甲基对硫磷为碳源生长的菌株,根据形态特征和16S r RNA基因序列同源性分析,对4株降解菌进行鉴定,利用高效液相色谱测定降解率,选取降解率最高的1株菌进行降解机制研究,以期将其应用于测定环境中甲基对硫磷残留的电位型微生物传感器的构建。结果表明,在甲基对硫磷初始浓度50 mg·L-1、30℃、p H 7.0的培养条件下培养7 d,4株菌对甲基对硫磷的降解率均在78%以上,其中1株菌的降解效率可达100%。16S r RNA基因序列测定表明,该菌株属于克雷伯氏菌属,命名为Klebsiella sp.MP-6。利用液相色谱-质谱联用对其降解产物的研究表明,菌株MP-6水解甲基对硫磷主要产生二甲基硫代磷酸(dimethyl thiophosphoric acid,DMTP)和对硝基苯酚(p-nitrophenol,PNP),极少部分PNP通过产生4-硝基邻苯二酚(4-nitrocatechol,4-NC)和1,2,4-苯三酚(1,2,4-BT)进一步代谢。结果表明,基于测定中间产物对硝基苯酚(p-nitrophenol,PNP)的电位响应信号,该菌株适用于构建测定海水及土壤等环境中有机磷农药的微生物传感器。     

Behavior of 78 pesticides and pesticide metabolites on four different Ultra-Bond gas chromatographic columns

The gas chromatographic (GC) elution order and relative retention time data (compared to aldrin) are presented for 78 pesticides and pesticide metabolites on 4 different types of commercially available 2 mm id Ultra-Bond columns including Ultra-Bond 20M (20M), Ultra-Bond 20SE (20SE), Ultra-Bond 20M coated with 1% OV-210 (OV-210), and Ultra-Bond 20M coated with 0.5% OV-210 + 0.65% OV-17 (mixed phase). Relative retention time data (compared to parathion) are also represented for 19 organophosphorus insecticides on the 4 Ultra-Bond columns evaluated. Corresponding 4 mm id Ultra-Bond columns were evaluated at the same time as the 2 mm id columns, and results and comparisons for these larger-diameter columns are discussed. These data indicate that, with aldrin as a reference peak, a complement of the mixed-phase column and either the 20M, the 20SE, or the OV-210 column represents a useful chromatographic tool for dual-column analysis of pesticide residues. The 2 mm id columns were more useful in chromatographing later-eluting pesticides whereas the corresponding 4 mm id columns were more useful in chromatographing earlier-eluting pesticides.     

Capillary gas chromatography with atomic emission detection for pesticide analysis in soil samples

A method for the simultaneous determination of 10 pesticides (organochlorines, organophosphorus compounds, and pyrethrins) in soils using capillary gas chromatography with atomic emission detection (GC-AED) is reported. Soil samples are first "cleaned-up" with 25 mL of an ascorbic acid solution (pH 2.15). The aqueous phase is extracted with ethyl acetate, and the solid residue is then extracted twice with 10 mL of ethyl acetate. The three resultant organic extracts are combined, concentrated to dryness, and reconstituted in 1 mL of acetone. The pesticides are selectively detected by monitoring chlorine and bromine in the first run and sulfur emission line wavelength in the second run. Each chromatographic run takes 19 min. Detection limits are between 25 and 75 pg, depending on the compound, which corresponds to 1.7 and 5.0 ng/g in the soil samples, respectively. Recoveries of the pesticides from spiked preparations result in an overall mean recovery of 95.3% (n = 120) at fortification levels ranging from 10 to 60 ng/g, depending on the compound. The method is reliable and can be useful for routine monitoring in soils.     

甲基对硫磷对红壤地区土壤微生物数量的影响

有机P农药是我国最重要一种农药类型,在农业生产上使用广泛。采用室内模拟方法,研究了甲基对硫磷对红壤地区不同类群土壤微生物数量的影响。研究结果表明,甲基对硫磷对土壤微生物数量的影响随甲基对硫磷添加的浓度、微生物类群和培养时间的不同而变化。添加100 mg/L和500 mg/L浓度甲基对硫磷能明显增加土壤细菌的数量,细菌数量的最大值出现在第10天左右;低浓度甲基对硫磷对土壤微生物数量影响不大。平板混合菌体培养实验证明,甲基对硫磷通过抑制或者杀灭某些种类土壤细菌,从而大大促进土壤生态系统中部分种类细菌数量的增殖。     

Degradation of Prototype Pesticides Submitted to Conventional Water Treatment Conditions: The Influence of Major Parameters

The behavior of several pesticides in aqueous solution, namely bifenthrin, amethrin (pyrethroid insecticides), endosulfan and endosulfan sulfate (organochlorine pesticides), disulfoton, methyl pyrimiphos, and phorate (organophosphorus pesticides), submitted to the conditions typically employed in water treatment stations was investigated. Continuous pesticide depletion was monitored by solid-phase microextraction sampling followed by gas chromatography–mass spectrometry analysis. The influence of major parameters (sodium hypochloride concentration, solution pH, and exposure time to ultraviolet (UV) light) was, thus, adequately established via two complementary approaches: factorial (2³, three variables—two levels) and Doehlert designs. Hence, the sodium hypochloride concentration and the solution pH produced distinct effects depending on the pesticide evaluated (for instance, acidic and basic media caused increasing rates of degradation for the organophosphorus/pyrethroid and organochlorine pesticides, respectively). Conversely, higher rates of degradation were achieved for all of the pesticides investigated when increased exposure times to UV radiation were employed. Finally, the exposure time to UV radiation that lead to complete degradation of disulfoton and endosulfan sulfate (organophosphorus and organochlorine pesticides, respectively) in aqueous media under ordinary conditions employed in water treatment stations was established; disulfoton and endosulfan sulfate were completely degraded after 10 and 40 h, respectively.     

Determination of acidic herbicides and related compounds in water and soil by capillary gas chromatography using a nitrogen-phosphorus detector

Methods are described for the determination of acidic herbicides and related compounds in water and soil. Eight acidic herbicides and related compounds were extracted from water using either dichloromethane or an XAD-2 resin column. The acidic moieties were derivatized with 2-cyanoethyldimethyl(diethyl)aminosilane. The derivatized compounds were separated using capillary gas chromatography and quantitated using a nitrogen-phosphorus detector. Extraction from water using dichloromethane or an XAD-2 resin column resulted in recoveries greater than 90% at 0.1 ppb with an average coefficient of variation (CV) of 6%. In soils extracted with aqueous acetonitrile-acetic acid and partitioned into dichloromethane, recoveries at 500 ppb were greater than 75% with an average CV of 3.3%. The methods are rapid and there are few interferences.