Biodegradation of phorate by bacterial strains in the presence of humic acid and metal ions.

Phorate is a systemic insecticide used to eradicate mites, insects, and nematodes. Extensive use of this organophosphate has engendered severe environmental concerns. The current research aimed to explore the kinetic pathways of phorate biodegradation in aqueous solutions. Two novel bacterial strains Pseudomonas aeruginosa strain PR1 (KP268772.1) and Pseudomonas sp. PR_02 (KP268773.1) were isolated, screened, and developed given their potential to degrade phorate. Mineralization of phorate was assayed with and without the addition of metal ions [Fe (II) and Cu (II)] and humic acid (HA). In 14 days, experiment both strains have consumed about 69%-94.5% (half-life from 3.58 to 6.02 days) of phorate. The observed biodegradation rate of phorate with Cu (II) in the system was 73% and 87%, with a half-life of 4.86 and 4.07 days for PR1 and PR2, respectively. The biodegradation of phorate using Fe(II) was 69% and 82%, with half-life periods 5.68 and 4.49 days. Meanwhile, incorporating HA, the phorate biodegradation was inhibited significantly, showing 71% and 85% degradation, with half-life periods of 6.02 and 5.02 days. The results indicated that both bacterial strains were able to mineralize phorate with PR2 > PR1. Summarizing, the inhibition in phorate biodegradation order under different conditions was as HA > Fe (II) > Cu (II). UV-visible measurements and gas chromatography-mass spectrometric assays indicated that the possible degradation pathway of phorate included ethoxy-phosphonothio-methanethiol S-mercaptomethyl-O,O-dihydrogen phosphorodithioate, diethyl-methylphosphonate, methane dithiol, ethanethiol, and phosphate, as the main metabolites identified. Therefore, it was concluded that the newly isolated Pseudomonas strains could be a potential candidates for biodegradation of phorate in a cost-effective, safe, and environmentally friendly alternative.

Pesticide Residues Identification by Optical Spectrum in the Time-Sequence of Enzyme Inhibitors Performed on Microfluidic Paper-Based Analytical Devices (µPADs).

Pesticides vary in the level of poisonousness, while a conventional rapid test card only provides a general "absence or not" solution, which cannot identify the various genera of pesticides. In order to solve this problem, we proposed a seven-layer paper-based microfluidic chip, integrating the enzyme acetylcholinesterase (AChE) and chromogenic reaction. It enables on-chip pesticide identification via a reflected light intensity spectrum in time-sequence according to the different reaction efficiencies of pesticide molecules and assures the optimum temperature for enzyme activity. After pretreatment of figures of reflected light intensity during the 15 min period, the figures mainly focused on the reflected light variations aroused by the enzyme inhibition assay, and thus, the linear discriminant analysis showed satisfying discrimination of imidacloprid (Y = -1.6525X - 139.7500), phorate (Y = -3.9689X - 483.0526), and avermectin (Y = -2.3617X - 28.3082). The correlation coefficients for these linearity curves were 0.9635, 0.8093, and 0.9094, respectively, with a 95% limit of agreement. Then, the avermectin class chemicals and real-world samples (i.e., lettuce and rice) were tested, which all showed feasible graphic results to distinguish all the chemicals. Therefore, it is feasible to distinguish the three tested kinds of pesticides by the changes in the reflected light spectrum in each min (15 min) via the proposed chip with a high level of automation and integration.

Dissipation behavior of phorate and its toxic metabolites in the sandy clay loam soil of a tropical sugarcane ecosystem using a single-step sample preparation method and GC-MS.

The dissipation of phorate in the sandy clay loam soil of tropical sugarcane ecosystem was studied by employing a single-step sample preparation method and gas chromatography with mass spectrometry. The limit of quantification of the method was 0.01 µg/g. The recoveries of phorate, phorate sulfoxide, phorate sulfone, and phorate oxon were in the range 94.00-98.46% with relative standard deviations of 1.51-3.56% at three levels of fortification between 0.01 and 0.1 µg/g. The Half-life of phorate and the total residues, which include phorate, phorate sulfoxide and phorate sulfone, was 5.5 and 19.8 days, respectively at the recommended dose of insecticide. Phorate rapidly oxidized into its sulfoxide metabolite in the sandy clay loam soil. Phorate sulfoxide alone accounted for more than 20% of the total residues within 2 h post-application and it was more than 50% on the fifth day after treatment irrespective of the doses applied. Phorate sulfoxide and phorate sulfone reached below the detectable level on 105 and 135 days after treatment, respectively as against 45 days after treatment for phorate residues at the recommended dose. Thus, the reasonably prolonged efficacy of phorate against soil pests may be attributed to longer persistence of its more toxic sulfoxide and sulfone metabolites.

QuEChERS method for the simultaneous quantification of phorate and its metabolites in porcine and chicken muscle and table eggs using ultra-high performance liquid chromatography with tandem mass spectrometry.

An analytical method to detect phorate and its metabolites, including phorate sulfone, phorate sulfoxide, phoratoxon, phoratoxon sulfone, and phoratoxon sulfoxide, in porcine and chicken muscles and table eggs was developed and validated. Extraction was performed using a quick, easy, cheap, effective, rugged, and safe method and analysis was conducted using ultra-high performance liquid chromatography-tandem mass spectrometry. Matrix-matched calibrations were linear over the tested concentrations, with determination coefficient ≥ 0.995 for all tested analytes in the different matrices. The limits of detection and quantification were 0.001 and 0.004 mg/kg, respectively. The calculated recovery rates at three fortification levels were satisfactory, with values between 74.22 and 119.89% and relative standard deviations < 10%. The method was applied successfully to commercial samples collected from locations throughout the Korean Peninsula, and none of them showed any traces of the tested analytes. Overall, the developed method is simple and versatile, and can be used for monitoring phorate and its metabolites in animal products rich in protein and fat.

Development of gold nanoparticles-based aptasensor for the colorimetric detection of organophosphorus pesticide phorate.

The present study reports a highly simple and rapid method for the detection of a widely used and extremely toxic organophosphorus pesticide, phorate. The detection employs a pesticide-specific aptamer as the recognition element and gold nanoparticles as the optical sensors. The aptamer, owing to its random coil structure, provides stability to the gold nanoparticles upon linking, thereby keeping the nanoparticles well dispersed. However, on the addition of the target pesticide, the aptamer acquires a rigid conformation resulting in the aggregation of the gold nanoparticles. Consequently, the color of the solution changes from red to blue and is easily observable with the naked eye. The proposed method was linear in the concentration range of 0.01 nM to 1.3 µm with the limit of detection as low as 0.01 nM. Moreover, the proposed assay selectively recognized phorate in the presence of other interfering substances and, thus, can be applied to real samples for the rapid and efficient screening of phorate.

Isolation and evaluation of potent Pseudomonas species for bioremediation of phorate in amended soil.

Use of phorate as a broad spectrum pesticide in agricultural crops is finding disfavor due to persistence of both the principal compound as well as its toxic residues in soil. Three phorate utilizing bacterial species (Pseudomonas sp. strain Imbl 4.3, Pseudomonas sp. strain Imbl 5.1, Pseudomonas sp. strain Imbl 5.2) were isolated from field soils. Comparative phorate degradation analysis of these species in liquid cultures identified Pseudomonas sp. strain Imbl 5.1 to cause complete metabolization of phorate during seven days as compared to the other two species in 13 days. In soils amended with phorate at different levels (100, 200, 300 mg kg(-1) soil), Pseudomonas sp. strain Imbl 5.1 resulted in active metabolization of phorate by between 94.66% and 95.62% establishing the same to be a potent bacterium for significantly relieving soil from phorate residues. Metabolization of phorate to these phorate residues did not follow the first order kinetics. This study proves that Pseudomonas sp. strain Imbl 5.1 has huge potential for active bioremediation of phorate both in liquid cultures and agricultural soils.

Determination of Organothiophosphate Insecticides in Environmental Water Samples by a Very Simple and Sensitive Spectrofluorimetric Method.

A simple, rapid and sensitive spectrofluorimetric method was developed for the determination of di-syston, ethion and phorate in environmental water samples. The procedure is based on the oxidation of these pesticides with cerium (IV) to produce cerium (III), and its fluorescence was monitored at 368 ± 3 nm after excitation at 257 ± 3 nm. The variables effecting oxidation of each pesticide were studied and optimized. Under the experimental conditions used, the calibration graphs were linear over the range 0.2-15, 0.1-13, 0.1-13 ng mL(-1) for di-syston, ethion and phorate, respectively. The limit of detection and quantification were in the range 0.034-0.096 and 0.112-0.316 ng mL(-1), respectively. Intra- and inter-day assay precisions, expressed as the relative standard deviation (RSD), were lower than 5.2 % and 6.7 %, respectively. Good recoveries in the range 86 %-108 % were obtained for spiked water samples. The proposed method was applied to the determination of studied pesticides in environmental water samples.

Brevibacterium frigoritolerans as a Novel Organism for the Bioremediation of Phorate.

Phorate, an organophosphorus insecticide, has been found effective for the control of various insect pests. However, it is an extremely hazardous insecticide and causes a potential threat to ecosystem. Bioremediation is a promising approach to degrade the pesticide from the soil. The screening of soil from sugarcane fields resulted in identification of Brevibacterium frigoritolerans, a microorganism with potential for phorate bioremediation was determined. B. frigoritolerans strain Imbl 2.1 resulted in the active metabolization of phorate by between 89.81% and 92.32% from soils amended with phorate at different levels (100, 200, 300 mg kg(-1) soil). But in case of control soil, 33.76%-40.92% degradation were observed. Among metabolites, sulfone was found as the main metabolite followed by sulfoxide. Total phorate residues were not found to follow the first order kinetics. This demonstrated that B. frigoritolerans has potential for bioremediation of phorate both in liquid cultures and agricultural soils.

Novel restricted access materials combined to molecularly imprinted polymers for selective solid-phase extraction of organophosphorus pesticides from honey.

A novel restricted access materials (RAM) combined to molecularly imprinted polymers (MIPs), using malathion as template molecule and glycidilmethacrylate (GMA) as pro-hydrophilic co-monomer, were prepared for the first time. RAM-MIPs with hydrophilic external layer were characterized by scanning electron microscopy and recognition and selectivity properties were compared with the restricted access materials-non-molecularly imprinted polymers (RAM-NIPs) and unmodified MIPs. RAM-MIPs were used as the adsorbent enclosed in solid phase extraction column and several important extraction parameters were comprehensively optimized to evaluate the extraction performance. Under the optimum extraction conditions, RAM-MIPs exhibited comparable or even higher selectivity with greater extraction capacity toward six kinds of organophosphorus pesticides (including malathion, ethoprophos, phorate, terbufos, dimethoate, and fenamiphos) compared with the MIPs and commercial solid phase extraction columns. The RAM-MIPs solid phase extraction coupled with gas chromatography was successfully applied to simultaneously determine six kinds of organophosphorus pesticides from honey sample. The new established method showed good linearity in the range of 0.01-1.0 µg mL(-1), low limits of detection (0.0005-0.0019 µg mL(-1)), acceptable reproducibility (RSD, 2.26-4.81%, n = 6), and satisfactory relative recoveries (90.9-97.6%). It was demonstrated that RAM-MIPs solid phase extraction with excellent selectivity and restricted access function was a simple, rapid, selective, and effective sample pretreatment method.

Surface-enhanced Raman spectroscopic analysis of phorate and fenthion pesticide in apple skin using silver nanoparticles.

Traditional pesticide residue detection methods are usually complicated, time consuming, and expensive. Rapid, portable, online, and real-time detection kits are the developing direction of pesticide testing. In this paper, we used a surface-enhanced Raman spectroscopy (SERS) technique to detect the organophosphate pesticide residue of phorate and fenthion in apple skin, for the purpose of finding a fast, simple, and convenient detection method for pesticide detection. The results showed that the characteristic wavenumbers of the two organophosphorus pesticides are more easily identified using SERS. We selected the Raman peaks at 728 cm(-1) of phorate and 1215 cm(-1) of fenthion as the target peaks for quantitative analysis, and utilized internal standards to establish linear regression models for phorate and fenthion. The detection limit was 0.05 mg/L for phorate and 0.4 mg/L for fenthion. This method can be used as a quantitative analytical reference for the detection of phorate and fenthion.

Detections of eleven organophosphorus insecticides and one herbicide threatening Pacific salmonids, Oncorhynchus spp., in California, 1991-2010.

California's surface water monitoring results from 1991 through 2010 were analyzed to determine whether 12 organophosphorus insecticides and herbicides (i.e., azinphos methyl, bensulide, dimethoate, disulfoton, ethoprop, fenamiphos, methamidophos, methidathion, methyl parathion, naled, phorate, and phosmet) and their degradates have been detected above maximum concentration limits (MCLs) in Pacific salmonid habitats. Methidathion, methyl parathion, phorate, phosmet, and the oxygen analogue of naled (DDVP) detections exceeded MCLs. Methyl parathion detections may be accounted for by monthly use trends, while methidathion detections may be explained by yearly use trends. There were inadequate phorate, phosmet, or DDVP data to evaluate for correlations with use.

Hypersalinity acclimation increases the toxicity of the insecticide phorate in coho salmon (Oncorhynchus kisutch).

Previous studies in euryhaline fish have shown that acclimation to hypersaline environments enhances the toxicity of thioether organophosphate and carbamate pesticides. To better understand the potential mechanism of enhanced toxicity, the effects of the organophosphate insecticide phorate were evaluated in coho salmon (Oncorhynchus kisutch) maintained in freshwater (<0.5 g/L salinity) and 32 g/L salinity. The observed 96-h LC50 in freshwater fish (67.34 ± 3.41 µg/L) was significantly reduced to 2.07 ± 0.16 µg/L in hypersaline-acclimated fish. Because organophosphates often require bioactivation to elicit toxicity through acetylcholinesterase (AChE) inhibition, the in vitro biotransformation of phorate was evaluated in coho salmon maintained in different salinities in liver, gills, and olfactory tissues. Phorate sulfoxide was the predominant metabolite in each tissue but rates of formation diminished in a salinity-dependent manner. In contrast, formation of phorate-oxon (gill; olfactory tissues), phorate sulfone (liver), and phorate-oxon sulfoxide (liver; olfactory tissues) was significantly enhanced in fish acclimated to higher salinities. From previous studies, it was expected that phorate and phorate sulfoxide would be less potent AChE inhibitors than phorate-oxon, with phorate-oxon sulfoxide being the most potent of the compounds tested. This trend was confirmed in this study. In summary, these results suggest that differential expression and/or catalytic activities of Phase I enzymes may be involved to enhance phorate oxidative metabolism and subsequent toxicity of phorate to coho salmon under hypersaline conditions. The outcome may be enhanced fish susceptibility to anticholineterase oxon sulfoxides.

Intoxicação por organofosforado em bovinos no Rio Grande do Sul / Poisoning by organophosphate in cattle in southern Brazil

An outbreak of organophosphate (ORF) poisoning in cattle occurred in the central-midwestern region of Rio Grande do Sul, Brazil. The water available for 49 cattle was contaminated with ORF and carbamate (CM). Twenty cows died after a clinical course that lasted for few hours. The classical clinical signs of over stimulation of the parasympathetic nervous system were observed, including motor incoordination, aggressiveness, drooling, muscle tremors and, on occasion, diarrhea. Significant morphological changes were not observed at necropsy or at histopathological examination. ORF e CM were detected by thin layer chromatography in tissue samples of two affected cattle and in a sample from the water consumed by the affected cattle. Additionally, two other water samples accessed by the affected cattle were positive for ORF. A quantitative analysis carried out by gas chromatography in the abomasum contents of an affected cow revealed 0.93µg/g of mancozebe (CM) and 0.07µg/g of phorate (ORF).

Descreve-se um surto de intoxicação por organofosforado (ORF) em bovinos na mesorregião centro ocidental do Rio Grande do Sul. A água fornecida a 49 bovinos foi contaminada com ORF e carbamato (CM). Vinte bovinos morreram após quadro clínico de poucas horas. Foram observados os clássicos sinais clínicos de hiperestimulação do sistema parassimpático incluindo incoordenação motora, agressividade, sialorreia, tremores musculares e, em alguns casos, diarreia. Na necropsia e histopatologia não foram observadas alterações morfológicas significativas. ORF e CM foram detectados por cromatografia em camada delgada em amostras de tecido de dois bovinos afetados. Adicionalmente, uma amostra da água consumida pelos bovinos foi positiva para ORF e CM e outras duas foram positivas para ORF. Uma análise quantitativa realizada por cromatografia gasosa no conteúdo do abomaso de um bovino afetado, revelou 0,93µg/g de mancozebe (CM) e 0,07 µg/g de forato (ORF).

[Research the role of gulonic acid lactone in the five kinds of organic phosphorus pesticide detection].

OBJECTIVE: To evaluate the protective effect of gulonic acid lactone in the gas chromatography-mass spectrometry system for detecting phorate, diazinon, dimethoate, methyl parathion, malathion five kinds of organic phosphorus pesticide. METHODS: By comparing the peak area changes of organic phosphorus pesticide configured with different concentrations (0, 0.3, 0.6, 0.9 and 1.2 mg/ml) of the gulonic acid lactone-methanol solution, and the concentrations (500 ng/ml) of organic phosphorus pesticide are same, to determine the best dosage of gulonic acid lactone. In the concentration, evaluate the protective effect of gulonic acid lactone on five kinds of organic phosphorus pesticide testing. RESULTS: When the concentration of gulonic acid lactone-methanol solution <1 mg/ml, the selected ion peak area of the five kinds organophosphorus pesticides detected by gas chromatography-mass spectrometry in the same conditions increases with the upward trend of its concentration ; when the concentration is equal to 1 mg/ml, the peak area reached the highest level, and then with the concentrations increased, no significant change in it. Diazinon's sensitivity increased by 4 times, phorate's sensitivity increased by 5 times, dimethoate, methyl parathion and malathion's sensitivity increased by 10 times, and the peak shape improved distinctly, tailing phenomenon disappears. CONCLUSION: Gulonic acid lactone can effectively improve the five kinds of organic phosphorus pesticide's sensitivity, improving the peak-type tailing and asymmetric phenomenon by the result of the active site. Quantitative bias can be effectively corrected caused by matrix effects. When the concentration is 1 mg/ml, it has the best effect of the compensation effect.

Development of a solid phase extraction method for agricultural pesticides in large-volume water samples.

An analytical method using solid phase extraction (SPE) and analysis by gas chromatography/mass spectrometry (GC-MS) was developed to determine trace levels of a variety of 41 agricultural pesticides and selected transformation products in high-elevation surface waters. Large-volume water sampling (up to 100L) was employed because it was anticipated that pesticide contamination, if present, would be at very low levels. The target compounds comprise pesticides (and selected oxygen transformation products) known to have been extensively used in agriculture in the San Joaquin Valley, CA, USA. Solid phase extraction using the polymeric resin Abselut Nexus was optimized to extract the pesticide analytes from water samples. A single determinative method using GC-MS with electron ionization was used for all the analytes. Recoveries from 100L of reagent water at 100pg/L and 1ng/L concentrations were generally greater than 75%, although dimethoate, disulfoton, and phorate were not recovered. Analysis of the extracts without cleanup yielded detection limits for the remaining 38 analytes between 0.1 and 30ng/L. A silica cleanup with separate analysis of 3 eluant fractions improved detection limits for 37 of the compounds to between 6 and 600pg/L in high-elevation surface waters.

Persistence and nematicidal efficacy of carbosulfan, cadusafos, phorate, and triazophos in soil and uptake by chickpea and tomato crops under tropical conditions.

The productivity of chickpea, Cicer arietinum (L.), and tomato, Solanum lycopersicum (L.), is adversely affected by root-knot nematode, Meloidogyne species. Nematode-resistant chickpea and tomato are lacking except for a few varieties and therefore grower demand is not met. The available nematicides, namely, carbosulfan, cadusafos, phorate, and triazophos, were, therefore evaluated for their efficacy and persistence in soil and crops to devise nematode management decisions. In alluvial soil, cadusafos was the most persistent nematicide followed by phorate, carbosulfan, and triazophos in that order. The percent dissipation of cadusafos was greater (P < 0.05) in chickpea than in tomato plots, which influenced its half-life in soil. Nematicide residues were differentially taken up by chickpea and tomato plant roots with active absorption continuing for up to 45 days. Cadusafos and triazophos were absorbed to greater extent (P < 0.05) in tomato than in chickpea. The translocation of residues to shoot was highest by day 15 for cadusafos and at day 45 for other nematicides, with carbosulfan residues translocated the most. Nematicide residue concentrations in shoots never exceeded those in roots, with residues in both roots and shoots persisting beyond 90 days. Nematicide residues in green seeds of chickpea and tomato fruits were all below the Codex/German MRLs of 0.02, including the Indian tolerances of 0.1 microg/g in fruits and vegetables. Cadusafos was found to be the most effective nematicide followed by triazophos against Meloidogyne incognita and reniform nematode, Rotylenchulus reniformis . Application of cadusafos (Rugby 10 G) or, alternatively, spray application of triazophos (Hostathion 40 EC) in planting furrows, both at 1.0 kg of active ingredient/ha, followed by light irrigation is recommended for the effective control of M. incognita and R. reniformis infestations on chickpea and tomato.

Adsorption of phorate, an organophosphorus pesticide, on vertisol.

Adsorption of phorate, an organophosphorus pesticide, on a vertisol soil was studied. The resulting data were well described by Freundlich and Langmuir adsorption isotherms. Adsorption was fast and the equilibrium was established within 8 h, which is comparatively less than reported previously. The mechanism of interaction between phorate and clay and humic acid extracted from the same soil was studied by Fourier-transform infrared (FTIR) spectroscopy. FTIR results suggested the formation of hydrogen bonds between carboxylic acid groups present in humic acid and appropriate electrophilic hydrogen atoms present in phorate. Also there is an indication of involvement of -P-O- group of phorate in the interaction with humic acid. However, the binding of phorate with clay minerals involves van der Waal forces of attraction.

Ionic liquid-based dispersive liquid-liquid microextraction followed high-performance liquid chromatography for the determination of organophosphorus pesticides in water sample.

Using 1-octyl-3-methylimidazolium hexafluorophosphate ([C(8)MIM][PF(6)]) ionic liquid as extraction solvent, organophosphorus pesticides (OPPs) (parathion, phoxim, phorate and chlorpyifos) in water were determined by dispersive liquid-liquid microextraction (DLLME) combined with high-performance liquid chromatography (HPLC). The extraction procedure was induced by the formation of cloudy solution, which was composed of fine drops of [C(8)MIM][PF(6)] dispersed entirely into sample solution with the help of disperser solvent (methanol). Parameters including extraction solvent and its volume, disperser solvent and its volume, extraction time, centrifugal time, salt addition, extraction temperature and sample pH were investigated and optimized. Under the optimized conditions, up to 200-fold enrichment factor of analytes and acceptable extraction recovery (>70%) were obtained. The calibration curves were linear in the concentration range of 10.5-1045.0 microg L(-1) for parathion, 10.2-1020.0 microg L(-1) for phoxim, 54.5-1089.0 microg L(-1) for phorate and 27.2-1089.0 microg L(-1) for chlorpyifos, respectively. The limits of detection calculated at a signal-to-noise ratio of 3 were in the range of 0.1-5.0 microg L(-1). The relative standard deviations for seven replicate experiments at 200 microg L(-1) concentration level were less than 4.7%. The proposed method was applied to the analysis of four different sources water samples (tap, well, rain and Yellow River water) and the relative recoveries of spiked water samples are 99.9-115.4%, 101.8-113.7% and 87.3-117.6% at three different concentration levels of 75, 200 and 1000 microg L(-1), respectively.

Soil column experiments used as a means to assess transport, sorption, and biodegradation of pesticides in groundwater.

Soil column experiments are used to investigate the fate of three pesticides of high, intermediate, and low solubility in groundwater: N- phosphonomethyl glycine (glyphosate); O,O-diethyl-S-[(ethylthio)methyl]phosphorodithioate (phorate); (2,4-dichlorophenoxy)acetic acid (2,4-D). Feed solutions are prepared by adding each pesticide (100 mg/L glyphosate, 50 micro g/L phorate, 50 mg/L 2,4-D) along with conservative tracer, KBr, in synthetic groundwater. The concentration of the pesticides in effluents is detected by ion chromatography (glyphosate, 2,4-D) and GC-FID (phorate). The Br(-) breakthrough curves are employed to estimate the dispersion coefficient and mean pore velocity in each column. Solute transport and reactive models accounting for equilibrium/non-equilibrium sorption and biodegradation are coupled with inverse modeling numerical codes to estimate the kinetic parameters for all pesticides.

Determination of organophosphorous pesticides in wastewater samples using binary-solvent liquid-phase microextraction and solid-phase microextraction: a comparative study.

A simple and efficient binary solvent-based two-phase hollow fiber membrane (HFM)-protected liquid-phase microextraction (BN-LPME) technique for moderately polar compounds was developed. Six organophosphorous pesticides (OPPs) (triethylphosphorothioate, thionazin, sulfotep, phorate, disulfoton, methyl parathion and ethyl parathion) were used as model compounds and extracted from 10-mL wastewater with a binary-solvent (toluene:hexane, 1:1) mixture. Some important extraction parameters, such as extraction time, effect of salt, sample pH and solvent ratio composition were optimized. BN-LPME combined with gas chromatography/mass spectrometric (GC/MS) analysis provided repeatability (R.S.D.s < or = 12%, n = 4), and linearity (r < or = 0.994) and solid-phase microextraction provides comparable of R.S.D.s < or = 13%, n = 4 and linearity (r < or = 0.966) for spiked water samples. The limits of detection (LODs) were in the range of 0.3-11.4 ng L(-1) for BN-LPME and 3.1-120.5 ng L(-1) for SPME at (S/N = 3) under GC/MS selective ion monitoring mode. In addition to high enrichment, BN-LPME also served as a sample cleanup procedure, with the HFM act as a filtering medium to prevent large particles and extraneous materials from being extracted. To investigate and compare their applicability, the BN-LPME and SPME procedures were applied to the detection of OPPs in domestic wastewater samples.