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Intensive use of pesticides requires innovative approaches for their removal from the environment. Here we report the method for degradation of dimethoate in water using non-thermal plasma needle and analyze kinetics of dimethoate removal and possible degradation pathways. The effects of dimethoate initial concentration, plasma treatment time, Argon flow rate and the presence of radical promoters on the effectiveness of proposed method are evaluated. With argon flow rate of 0.5 slm (standard litres per minute) 1 × 10−4 M dimethoate can be removed within 30 min of treatment. Using UPLC analysis it was confirmed that one of the decomposition products is dimethoate oxo-analogue omethoate, which is in fact more toxic than dimethoate. However, the overall toxicity of contaminated water was reduced upon the treatment. The addition of H2O2 as a free radical promoter enhances dimethoate removal, while K2S2O8 results with selective conversion to omethoate. Using mass spectrometry in combination with the theoretical calculations, possible degradation pathways were proposed. The feasibility of the proposed method for dimethoate degradation in real water samples is confirmed. The proposed method is demonstrated as a highly effective approach for dimethoate removal without significant accumulation of undesirable toxic products and secondary waste. © 2019 Elsevier Ltd

Despite the tremendous achievements of existing sensing techniques, sensitive and portable sensing of organophosphorus pesticides (OPs) in a non-polluting manner remains a challenging issue. This work proposed a facile colorimetric paper sensor using γ-MnOOH nanowires (NWs) as a degradable nanozyme and 3,3′,5,5′-tetramethylbenzidine (TMB) as a chromogenic indicator for rapid and sensitive screening of OPs and acetylcholinesterase (AChE) activity. The sensing mechanism was based on the easy disintegration of the oxidase-like γ-MnOOH NWs into invalid Mn2+ ions by the selective reaction with thiocholine (TCh) produced by AChE and acetylthiocholine iodide (ATCh), triggering a remarkable activity loss of MnOOH nanozymes towards TMB oxidation. The concentration of OPs, as an AChE inhibitor, was measured by the changes in absorbance at 652 nm or blue color of oxTMB products. Such detection platform in solution state achieved relatively low limits of detection (LODs) for AChE activity (0.007 mU mL−1), and for two typical OPs, i.e., omethoate (0.35 ng mL−1) and dichlorvos (0.14 ng mL−1), respectively. Further, the portable assembly of such AChE-nanozyme tandem reaction on test paper performed well, reaching LODs of 0.1 mU mL−1 for AChE, 10 ng mL−1 for omethoate, and 3 ng mL−1 for dichlorvos, respectively. Meanwhile, this sensing system showed great selectivity and anti-interfering capacity in both solution and solid states, and worked well in real serum and vegetable samples. The abovementioned results, along with evidence of its good ecological sustainability, demonstrated the superiority of this well-performing platform for application in the food, environmental, and medical fields.

Sulfoxaflor is the first commercially available sulfoximine insecticide, which exhibits highly efficacy against many sap-feeding insect pests and has been applied as an alternative insecticide against cotton aphid in China. This study was conducted to investigate the risk of resistance development, the cross-resistance pattern and the potential resistance mechanisms of sulfoxaflor in Aphis gossypii. A colony (SulR strain) of A. gossypii with 245-fold resistance, originated from Xinjiang field population, was established by continuous selection using sulfoxaflor. The SulR strain has developed cross-resistance to imidacloprid (80.8-fold), acetamiprid (19.3-fold), thiamethoxam (10.0-fold), and flupyradifurone (107.5-fold), while no cross-resistance was detected to malathion, omethoate, bifenthrin, methomyl, and carbosulfan. Piperonyl butoxide and S, S, S-tributyl phosphorotrithioate could significantly increase the toxicity of sulfoxaflor to the SulR strain by 5.99- and 4.18-fold, respectively, whereas no synergistic effect with diethyl maleate was observed. The activities of P450s and carboxylesterase were significantly higher in the SulR strain than that in the SS strain. Further gene expression determination demonstrated that nine P450 genes were significantly increased in SulR strain and suppression the expression of CYP6CY13 and CYP6CY19 by RNAi significantly increased the susceptibility of SulR adult aphids to sulfoxaflor. These results demonstrated that the enhancing detoxification by cytochrome P450 monooxygenase may be involved in A.gossypii resistance to sulfoxaflor.

The risk of exposure of honey bees to the presence of insecticides in melliferous plants is higher than previously reported. Therefore, monitoring insecticide residues in these plants is of great importance to honey bee safety. A novelty of the present research was the development of an innovative procedure for determination of residues of 142 insecticides in weeds and agricultural crops among melliferous plants. Phacelia, buckwheat, rape, common dandelion, cornflower and clover were selected for testing. Samples were extracted via QuEChERS. Two single sorbents (Z-Sep and Chitosan) and two combinations of sorbents (PSA/C18/ENVI-Carb/MgSO4, PSA/GCB/MgSO4) were tested. The matrix effect was applied as the main criterion for assessment of the method's effectiveness. The best sorbent for preparation of: (i) common dandelion samples was PSA/GCB/MgSO4, (ii) rape, cornflower and clover samples - PSA/C18/ENVI-Carb/MgSO4 sorbent and (iii) phacelia and buckwheat samples - Z-Sep sorbent. The developed procedure was applied for quantification of insecticide residues in 41 melliferous plant samples to estimate exposure of honey bees to pesticides through calculation of the hazard quotient (HQ). In total, 12 different insecticides were detected. The presence of neonicotinoid insecticides was found 7 times. The residues most frequently identified in melliferous plants were deltamethrin, dimethoate, and its metabolite, omethoate. An increased insecticide risk to honey bees was found for 4.9% and 9.8% of samples, for the oral and contact dose, respectively. This is why the hazard of melliferous plant residues was considered elevated for honey bees. The results clearly demonstrated that the approach developed provides reliable, simple and rapid determination of insecticides in melliferous plants, which is of great importance to honey bee safety.

An efficient method for the rapid extraction and clean-up of 20 pesticide residues from polyphenol-rich agricultural samples (tea, apple, broccoli, and shallot) for analysis by UPLC-MS/MS was developed. Following extraction, PVPP was used to precipitate polyphenols, supernatant was diluted to minimize matrix effects. Homogenized samples were vortexed in acetonitrile prior to cleanup with a combination of PVPP (150 mg), PSA (50 mg) and GCB (10 mg). Supernatant (1 mL) was filtered and diluted 10-fold before analysis. In 4 agricultural products that usually produce high interference, the matrix effects were overcome for all pesticides expect in green and oolong tea for acephate, omethoate, dinotefuran and nitenpyram. Mean recoveries ranged from 73% to 106%, and RSD ≦ 13%. Limits of quantification ranged from 0.01 to 0.02 mg kg−1. PVPP as one of excellent QuEChERS material combined with dilution was verified as a promising method for multiple pesticide residues analysis in complex matrices.

Omethoate, an organophosphorous pesticide, can cause a variety of health effects, especially the decrease of cholinesterase activity. The aim of this study is to explore the association of genetic polymorphisms of telomere binding proteins with cholinesterase activity in omethoate-exposed population. Cholinesterase activities in whole blood, red blood cell and plasma were detected using acetylthiocholine and dithio-bis-(nitrobenzoic acid) method; Genetic Genotyping of POT1 rs1034794, POT1 rs10250202, TERF1 rs3863242 and TERT rs2736098 were performed with PCR-RFLP. The cholinesterase activities of whole blood, red blood cells and plasma in exposure group are significantly lower than that of the control group (P 0.001). Multivariate analysis indicates that exposure group (b = - 1.016, P 0.001), agender (b = 0.365, P 0.001), drinking (b = 0.271, P = 0.004) and TERF1rs3863242 (b = - 0.368, P = 0.016) had an impact on cholinesterase activities. The results suggest that individual carrying AG+GG genotypes in TERF1 gene rs3863242 polymorphism were susceptible to damage in cholinesterase induced by omethoate.

Quantum chemical calculations were performed to investigate the mechanism of OH radical-initiated atmospheric oxidative degradation of dimethoate (DMA). Geometrical parameters and vibrational frequencies were calculated at the MPWB1K/6-31 + G (d,p) level and the energies of reactants, transition states, intermediates, and products were calculated at the MPWB1K/6-311 + G (3df,2p) level. Rate constants of the key elementary steps with positive potential barriers were obtained by utilizing the canonical variational transition-state (CVT) theory in combination with the small curvature tunneling (SCT) correction over a temperature range of 273–333 K. Both H abstraction from the CH3 group (in NHCH3 group) and the generation of more toxic omethoate (OMA) via OH-adduct are barrierless processes, which reveals that these pathways are thermodynamically favorable and OMA could be one of the major intermediates in DMA degradation process in the atmosphere. The calculated rate constants provide new insights into the lifetime of dimethoate in the atmosphere.

Highlights • GPSD plasma was successfully applied to degrade OP residues from L. barbarum. • GPSD plasma exposure didn’t induce any changes in the fruit quality. • Electrical and optical characteristics of the plasma discharge were analysed. • The degradation efficiency of OP residues reached 99.55% and 96.83% at 10 kV. Abstract Pesticides are widely used in commercial goji Lycium barbarum cultivation to prevent damage of the delicate fruits by insects, potentially leading to insecticide and fungicide residues at levels dangerous to human health. In this study, removal of organophosphorus pesticide (OP) residues (i.e. omethoate and dichlorvos) from the surface of L. barbarum was conducted using a gas phase surface discharge (GPSD) plasma system. ICCD and GC-MS measurements showed that a homogeneous and uniform GPSD glow-like plasma could be achieved and the efficiency of OP residues degradation greatly depended on the applied voltage and plasma exposure time, with 99.55% and 96.83% efficiency recorded for omethoate and dichlorvos (DDVP), respectively after 30 min GPSD plasma exposure at the discharge voltage of 10 kV. FT-IR and chemical analysis of the intermediates produced during GPSD exposure revealed that the omethoate and DDVP molecules could be completely degraded into nontoxic species, at the appropriate dosage of GPSD plasma exposure, without compromising the quality of L. barbarum. Based on the experimental and simulation results, a mechanism of OP degradation attributed to energetic electrons and highly reactive species generated by GPSD plasma was proposed.

Organophosphorus pesticides (OPs) are widely used in pest control. The residual OPs can cause pollution to the environment and harm to the human body. Although OPs can inhibit the activity of acetylcholinesterase (AChE) and lead to neurological diseases, it also provides enlightenment for the development of a simple and sensitive method for the detection of OPs. Herein, we report a colorimetric sensor array using nanozymes (Fe-N-C nanozymes and Cu-N-C nanozymes) combined with natural enzymes to discriminate eight OPs (Iprobenfos (Ipr), Diazinon (Dia), Crotoxyphos (Cro), Bromophos ethyl (Bro), Dipterex (Dip), Chlorpyrifos methyl (Chl), Ethion (Eth), and Omethoate (Ome)) through a cascade reaction system. Surprisingly, eight OPs were successfully identified in tap water at 1 ng mL−1.

Development of selective, ultra-sensitive, rapid and facile methods for the detection of chemical residues of toxic pesticides and hazardous chemicals are quite important in food safety, environmental monitoring and safeguarding public health. Herein, we presented a fluorescent turn-on aptasensor based on sulphur-doped graphene quantum dot (S-GQD) utilizing specific recognition and binding property of aptamer for the ultra-sensitive and selective detection of omethoate (OM) which is a systemic organophosphorus pesticide. The detection method is based on tuning aggregation-disaggregation mechanism of S-GQD by way of conformational alteration of the recognition probe. Fluorescence ‘turn-on’ process includes aggregation-induced quenching of S-GQD with aptamer via S-GQD-aptamer complex formation and its subsequent fluorescence recovery with the addition of OM by structural switching of S-GQD-aptamer complex to aptamer-omethoate complex. The reported ‘switch-on’ aptasensor has exhibited a low limit of detection of 0.001 ppm with high selectivity for OM over other pesticides.

This study investigated the levels of highly toxic pesticides (HTPs) in 6554 vegetable and fruit samples from 31 regions of China, along with the associated risk of dietary exposure for the population between 2014 and 2017. 18 HTPs were detected in 325 (4.96%) samples, and the levels of HTPs in 103 (1.57%) samples were found to be higher than the maximum residue limits (MRLs) of China. The rate of detection of HTPs in six types of vegetables and fruits, in a decreasing order, was found to be as follows: eggplant (8.84%) >grape (5.58%) >tomato (5.43%) >cucumber (5.43%) >pear (3.12%) >apple (2.30%). The level of contamination of HTPs was found to be higher in vegetables compared with fruits. The vegetable and fruit samples with the highest percentages of HTPs exceeding MRLs were found in eggplants from Guangxi (20%) and grapes from Inner Mongolia (12.5%), respectively. Both, the average target hazard quotient (THQ) of a single highly toxic pesticide (HTP) and the average hazard index (HI) of the mixture of HTPs for adults and children from vegetables and fruits from the 31 regions were found to be less than one. Omethoate, carbofuran, ethoprophos, triazophos, and phorate were identified as the major contributors to the average HI for vegetables, and carbofuran, ethoprophos, omethoate, phorate, and phosphamidon were identified as the primary contributors to the average HI for fruits. The results of this study revealed that HTPs in vegetables and fruits did not cause any significant chronic risk of dietary exposure. The detection of HTPs exceeding MRLs in some of the samples implied that appropriate management guidelines for HTPs should be implemented to protect the health of the consumers.

A double-film screening card, composed of an enzyme (acetylcholinesterase, AChE) and its substrate (indoxyl acetate) films, was developed for simple and rapid screening of organophosphate and carbamate pesticide residues. On the card, indoxyl acetate is decomposed by AChE to produce a blue-green compound. Compared with the speed of inhibition of AChE activity by pesticides, The color developing speed is relatively slow. When a sample solution with pesticides is dropped in the test window, this reaction of AChE is efficiently and rapidly inhibited to a degree depending on the level of pesticide. Any remaining active AChE would hydrolyze indoxyl acetate to show color. Qualitative and quantitative detection of pesticide residues could be achieved based on the color intensity. The selected suitable carrier films containing the enzyme and substrate were hydrophilic materials that were capable of adsorbing and releasing the full doze of enzyme or substrate. The optimum materials for containing AChE and indoxyl acetate on the card were glass fiber RB65 and polyester fiber VL78, respectively. The optimum quantities of AChE and indoxyl acetate per film in the test window were 15 μL of 3500 U/mL and 10 μL of 100 mM, respectively. The maximum color intensity was reached at room temperature in 15 min. The limits of detection were up to 0.05 μg/mL for phoxim, 0.1 μg/mL for acephate, 0.5 μg/mL for malathion, 0.5 μg/mL for omethoate, 0.04 μg/mL for carbofuran and 0.09 μg/mL for aldicarb. The card showed good reproducibility and high sensitivity when applied to real food samples.

A thiamethoxam-resistant strain of cotton aphid (ThR) displayed a 13.79-fold greater resistance to thiamethoxam than a susceptible cotton aphid (SS) strain. Piperonyl butoxide (PBO) and triphenyl phosphate (TPP) synergistically increased the toxicity of thiamethoxam in the resistant strain, whereas diethyl maleate (DEM) did not exhibit significant synergistic effects. Bioassay results indicated that the ThR strain developed increased levels of cross-resistance to bifenthrin (11.71 fold), cyfluthrin (17.90 fold), esfenvalerate (6.85 fold), clothianidin (6.56 fold), methidathion (5.34 fold) and alpha-cypermethrin (4.53 fold) but did not show cross-resistance to malathion, omethoate, acephate, chlorpyrifos, methomyl, sulfoxaflor or imidacloprid. PBO and TPP increased bifenthrin toxicity in the resistant strain by 2.38 and 4.55 fold, respectively. Quantitative real-time PCR results indicated that the mRNA expression levels of the α1, α4-1, α4-2, α5 and α7 subunits decreased significantly by 3.32, 1.60, 2.05, 5.41 and 1.48 fold, respectively, in the resistant strain compared with those in the susceptible strain. However, significant differences were not observed in the expression of the α2, α3 and β1 subunits. No target-site mutations within the α1, α2 and β1 subunits of nicotinic acetylcholine receptors (nAChRs) were detectable in the ThR strain. In conclusion, the levels of thiamethoxam resistance and cross-resistance to other insecticides observed in the ThR strain are likely regulated by two mechanisms, which include the overexpression of detoxification-related P450s and esterase. These results should be useful for the understanding thiamethoxam resistance mechanism and the management of insecticide-resistant cotton aphids in China.

The absorption, distribution, metabolism and primary risk evaluation data of four neonicotinoids and two organophosphate insecticides in tea plant (Camellia sinensis L.) were compared. 22 neonicotinoid metabolites and 2 organophosphate metabolites were identified. The amount ratio of each neonicotinoid metabolite to its corresponding parent (M/P) was lower than 0.076 in the treated time. The organophosphates (omethoate and methamidophos) increased sharply, with M/Ps as high as 1.111 and 0.612. The risks evaluation of insecticides and their metabolites in treated leaves on day seven showed that the chronic risk was from the lowest 0.0759 (clothianidin) to highest 43.6409% (dimethoate), and the acute risk was highest 0.0370 for all targets. The calculated combined toxicity of leaves treated with acephate reached 1.5 folds in mature, 1.5 folds in tender leaves than no metabolites, and which of dimethoate were 2.1 folds in mature and 3.7 folds in tender leaves.

Rhopalosiphum padi (Linnaeus) and Sitobion avenae (Fabricius) are the predominant pests coexisting on wheat plants. In this study, the susceptibilities of 29 R. padi and 30 S. avenae populations from 15 provinces in China to pyrethroids (beta-cypermethrin and bifenthrin), neonicotinoids (imidacloprid and thiamethoxam), organophosphates (omethoate and chlorpyrifos) and macrolides (avermectin) were determined during 2018–2019. The median lethal insecticide concentrations (LC50) indicated that R. padi was more sensitive than S. avenae to most of the insecticides. Monitor results showed that most wheat aphid populations were moderately resistant to pyrethroids. Two R. padi populations were highly resistant to beta-cypermethrin with 127.3-fold and 442.8-fold resistance ratio (RR), and two were highly resistant to bifenthrin (RR of 293.9 and 320.6, respectively). One S. avenae population was highly resistant to beta-cypermethrin (RR of 136.8) and one was highly resistant to bifenthrin (RR of 313.4). All populations of two wheat aphids exhibited low to moderate resistance to neonicotinoids (RR

OBJECTIVE The aim of this study was to explore the association between genetic variations in telomere pathway genes and the level of hydrogen peroxide (H2O2) in omethoate exposure workers. METHODS A total of 180 omethoate exposure workers and 115 healthy controls were recruited. The level of H2O2 in plasma was determined with molybdenic acid colorimetry. Polymerase chain reaction and restriction fragment length was used to detect polymorphisms in POT1 rs1034794, POT1 rs10250202, TERF1 rs3863242, and TERT rs2736098. RESULTS The level of H2O2 in exposure group (4.26 ± 0.71) was significantly higher than that in control group (3.29 ± 0.46). Generalized linear models indicated that risk factors for the increase H2O2 level were exposure [β(95 % CI) = 0.951 (0.806, 1.096), P

A novel magnetic mesoporous nanomicrospheres Fe3O4@SiO2@mTiO2 were synthetized and characterized by a series of techniques including FE-TEM, EDS, FE-SEM, PXRD, XPS, BET, TGA as well as VSM, and subsequently tested as a photocatalyst for the degradation of Acephate, Omethoate, and Methyl parathion under UV irradiation. The well-designed nanomicrospheres exhibit a pure and highly crystalline anatase TiO2 layer, large specific surface area, and high-magnetic-response. Photocatalytic degradation of the three organophosphorus pesticides (OPPs) and the formation intermediates were identified using HPLC, TOC-Vcpn, IC, pH meter and GC-MS. Acephate, Omethoate, and Methyl parathion disappeared after 45min, 45min, and 80min UV illumination, respectively. At the end of the treatment, the total organic carbon (TOC) of the OPPs was reduced 80-85%. The main mineralization products were SO4(2-), NO3(-) and PO4(3-) and Omethoate additionally formed NO2(-). Based on the results, we proposed the photocatalytic degradation pathways for Acephate, Omethoate, and Methyl parathion.

The effect of different kinds of pesticide residues in grapes on alcoholic fermentation by Saccharomyces cerevisiae was evaluated. Among four types of pesticides added into the grape slurry, omethoate, triadimefon and cyhalothrin did not inhibit the alcoholic fermentation at their proposed spraying concentration of 0.21, 0.10 and 0.10 g L−1, respectively, whereas chlorothalonil concentration above 0.03 g L−1 behaved significantly negative influence on both S. cerevisiae growth and alcoholic fermentation efficiency. When the chlorothalonil concentration was lower than 0.01 g L−1, the fermentation proceeded smoothly without any degradation of chlorothalonil. Considering the cumulative toxicity and adverse effect of chlorothalonil on fermentation, chlorothalonil hydrolytic dehalogenase (Chd) extracellularly expressed from the recombinant Bacillus subtilis WB800 was used to pretreat the chlorothalonil-contaminated grape slurry. After treatment by the Chd enzyme in an activity of 7.25 mU L−1 slurry for 60 min, the inhibition effect could be substantially eliminated even at an initial concentration of 0.10 g L−1 chlorothalonil. This study provides a potential approach for solving the conflict in fermentation industry with pesticides inhibition.

A new methodology for the retrospective screening of pesticide metabolites in ambient air was developed, using liquid chromatography coupled to Orbitrap high-resolution mass spectrometry (UHPLC-HRMS), including two systematic workflows (i) post-run target screening (suspect screening) and (ii) non-target screening. An accurate-mass database was built and used for the post-run screening analysis. The database contained 240 pesticide metabolites found in different matrixes such as air, soil, water, plants, animals and humans. For non-target analysis, a "fragmentation-degradation" relationship strategy was selected. The proposed methodology was applied to 31 air samples (PM10) collected in the Valencian Region (Spain). In the post-target analysis 34 metabolites were identified, of which 11 (3-ketocarburan, carbofuran-7-phenol, carbendazim, desmethylisoproturon, ethiofencarb-sulfoxide, malaoxon, methiocarb-sulfoxide, N-(2-ethyl-6-methylphenyl)-L-alanine, omethoate, 2-hydroxy-terbuthylazine, and THPAM) were confirmed using analytical standards. The semiquantitative estimated concentration ranged between 6.78 and 198.31 pg m(-3). Likewise, two unknown degradation products of malaoxon and fenhexamid were elucidated in the non-target screening.

This study was designed to investigate organophosphorus pesticides (OPs) concentrations in fresh vegetables and estimate potential health risks to inhabitants. A total of 214 samples of seven types of vegetables were collected from Changchun, the capital of Jilin province, one of the most important vegetable production areas. The eleven OPs were analyzed by gas chromatography coupled with flame photometric detector (GC-FPD). Results showed that 23.4% of samples contained OPs above maximum residue limit (MRL), 68.7% of samples below MRL and only 7.9% of samples were found free of OPs. Detection rates of OPs decreased in the following order: diazinon (82.2%) > phorate (45.8%) > dimethoate (29.4%) > parathion-methyl (27.6%) > omethoate (23.8%) > dichlorvos (22.9%) > fenitrothion (21%) > fenthion (18.7%) > parathion (18.2%) > methamidophos (17.3%) > malathion (12.1%). The OPs levels were higher for leafy than for non-leafy vegetables. The percentages of OPs above MRL: welsh onion (82.5%) > radish (37.5%) > pepper (17.2%) > Chinese cabbage (14.3%) > cucumber (3.2%) > eggplant (2.9%) > tomato (0%). 49.5% samples contained two or more OPs. The average target hazard quotients (ave THQ) were all less than one and the average Hazard Index (ave HI) for adults and children were 0.448 and 0.343, respectively. It is concluded that inhabitants who are exposed to average OPs levels may not be endangered by health risk.

Organophosphate insecticides (OI) are widely used. To humans the main routes of exposure are skin and inhalation. For this, keratinocytes (HaCaT) and bronchial cells (NL-20) were used as cell culture models to evaluate the effects of OI. The aim of this study was to evaluate the effect of four OI on HaCaT and NL-20 cells: azinphos-methyl, (AM); parathion-methyl (PM); omethoate (OM); and methamidophos (MET). Cells were exposed to 0.1, 1 and 10 μg/μL of each. Results showed a decrease in cell viability in both cell lines. Viability of the NL-20 cell line decreased with the three concentrations of OM. All differences were significant (p < 0.05). Genotoxic damage, evaluated through the comet assay, was observed in both cell lines with AM. NL-20 cell line was more sensitive than HaCaT. Higher concentrations of the insecticides except MET, induced cell death. MET caused DNA damage in HaCaT cells at all concentrations. Differences were significant (p < 0.05). Both cell lines revealed the presence of single membrane vacuoles of different sizes when exposed to 1 μg/μL of each insecticide. Quantitative real time-polymerase chain reaction (RT-qPCR) showed an increase of BN1 gene in HaCaT by effect of AM and MET at 1 μg/μL. In conclusion, all the insecticides induced different levels of cyto and genotoxic effects in both cell lines.

In this work, electrodeposition, a simple, fast and convenient method, was used to prepare a superhydrophilic 3D tree-like silver (Ag) microstructure and a acetylcholinesterase (AChE) biosensor was constructed based on 3D tree-like Ag. Several advantages were illustrated in this work as follows: the electrodeposition method provided uniform distribution and stable adhesion of the material at the electrode surface; the superhydrophilic property of the prepared material could increase the contact area between the electrode surface and the liquid (solid–liquid interphase); and the rough structure of the 3D tree-like Ag could provide a good microenvironment for the enzyme load. These features all greatly improved the sensitivity and stability of biosensors. Under the optimal conditions, the AChE/3D tree-like Ag/GCE biosensor obtained a high sensitivity of 0.056 μA mM−1, a wide linear range from 10-13 M to 10-7 M, and a low detection limit of 1.26 × 10-14 M (calculated for S/N = 3), which was much smaller than the maximum amount permitted by Chinese National Standards (20 μg/kg). The prepared biosensor also obtained excellent reproducibility and stability. Moreover, the feasibility of the prepared biosensor to detect omethoate in real samples has been confirmed with good recovery (97.2%-102.2%).

Advanced nanocomposite from silica-fume based MCM-41 and cobalt oxide (Co3O4/SF-MCM-41) which precipitated by green techniques in the presences of Pomegranate leaves extract as reducing reagent. The formation of the Co3O4/SF-MCM-41composite was confirmed by different studied analytic techniques and applied as novel photocatalyst in the visible light oxidation of Omethoate pesticide. The composite is of stunning surface area (742 m2/g) and low band gap energy value (1.53 eV) which giving it promising photocatalytic performances. It showed highly effective photocatalytic activity which reflected in a complete degradation of 50 mg/L, 100 mg/L, 150 mg/L, 200 mg/L and 250 mg/L of Omethoate after 30 min, 50 min, 80 min, 100 min, and 120 min, respectively using 0.25 g of Co3O4/SF-MCM-41. This associated with complete degradation of the detected TOC content within the same time intervals. The detected intermediate organic materials of (CH3O)3P(O), (CH3O)2P(O)SCH3, CH3NHC(O)CH2SH, CH3NHC(O)CH2SCH3, and NH2C(O)CH2SCH3 were identified as oxidizing products during the degradation steps and all of them were converted into NO3−, SO42-, PO43-, and CO2 as final products. The composite is of reusability value and the hydroxyl radicals were identified as the controlling radicals during the oxidation process.

The English grain aphid, Sitobion avenae Fabricius, is one of the major wheat pests distributed worldwide. Insecticide application is typically effective for controlling S. avenae, However, S. avenae has developed resistance to multiple insecticides. Thus, it is crucial to elucidate resistance mechanisms in S. avenae. In this study, the mechanisms of resistance to imidacloprid in S. avenae and the risk of cross resistance to other insecticides were investigated. An imidacloprid resistant strain (SA-R) of S. avenae was established via continuous imidacloprid selection with 42.7-fold resistance compared with the susceptible population (SA-S). There was cross resistance in SA-R between imidacloprid and other insecticides tested (acetamiprid, abamectin, chlorpyrifos, and omethoate), with ratios ranging from 10.7- to 24.7-fold higher than SA-S. S, S, S-tributyl phosphorotrithioate (TPP), piperonyl butoxide (PBO), and diethyl maleate (DEM) had synergism with imidacloprid in the SA-R strain with 2.85-, 3.59-, and 2.14-fold reductions, respectively, in LC50 values. Additionally, the activities of cytochrome P450 (P450), glutathione-S-transferases (GST), and carboxylesterase (COE) were significantly higher by 2.69-, 1.42-, and 1.39-fold in the SA-R strain than in the SA-S strain. Based on the S. avenae transcriptome database, 11 P450, two COE, four GST, and two esterase (EST) genes that were significantly induced by imidacloprid were selected to compare gene expression levels between SA-R and SA-S. Fourteen detoxification genes of the 19 tested from the SA-R strain were overexpressed compared to those of the SA-S strain. Silencing of CYP6A14-1, CYP307A1, GST1-1-1, and COE2 by dsRNA feeding resulted in increased susceptibility of SA-R aphids to imidacloprid. These results provide evidence that detoxification genes including CYP6A14-1, CYP307A1, GST1-1-1, and COE2 contribute to resistance to imidacloprid in S. avenae, which was confirmed by RNA interference (RNAi) feeding.

To monitor pesticide residues in cowpea and assess the potential public health risk, 433 fresh cowpea samples from Hainan province (2012 and 2013) were collected and the presence of 20 organophosphoate, carbamate and pyrethroid was determined. A screening analysis consisting of a dietary exposure assessment of pesticide residue was performed using a deterministic approach-point estimate of exposure. The results indicated the most important residues were triazophos, carbofuran, isocarbophos, phoxim and omethoate. The estimated daily intakes (EDIs) of those pesticides were 72.89%, 27.45%, 12.35%, 12.19% and 9.15% of Acceptable Daily Intake (ADI) respectively. Then a probabilistic approach applied on the residues of concern demonstrated that exposure from triazophos exceeded the ADI at P99.9. A relative potency factors method was employed to ascertain that exposure to triazophos is a cause for concern.

A modified residual contact vial bioassay (RCV) in which a small aliquot (1 μl) of water was supplemented to minimize control mortality was established as a rapid insecticide resistance monitoring tool for the western flower thrips, Frankliniella occidentalis. Based on the RCV scheme, diagnostic doses for seven insecticides that are widely used for F. occidentalis control were determined at 8 h post-treatment using a susceptible RDA strain. The diagnostic doses for five insecticides (chlorfenapyr, acrinathrin, spinosad, emamectin benzoate and thiamethoxam) were in the range of 0.03 to 0.42 μg− 1 cm2 and were readily applicable for the detection of resistance levels. In the case of the remaining two insecticides (omethoate and imidacloprid), however, the estimated diagnostic doses were too high (3.28 and 12.4 μg− 1 cm2, respectively) to form a viscous film over the inner wall of the treated vial, thereby limiting their use for resistance detection. Thus, the performance of RCV in detecting resistance to the five insecticides was evaluated for five local populations of F. occidentalis. The RDA strain exhibited 100% mortality to all insecticides tested, whereas field populations collected from horticultural glass houses generally showed remarkably reduced mortality (

Pardosa pseudoannulata is an important predatory enemy against insect pests, such as rice planthoppers and leafhoppers. In order to understand the insecticide selectivity between P. pseudoannulata and insect pests, two acetylcholinesterase genes, Pp-ace1 and Pp-ace2, were cloned from this natural enemy. The putative proteins encoded by Pp-ace1 and Pp-ace2 showed high similarities to insect AChE1 (63% to Liposcelis entomophila AChE1) and AChE2 (36% to Culex quinquefasciatus AChE2) with specific functional motifs, which indicated that two genes might encode AChE1 and AChE2 proteins respectively. The recombinant proteins by expressing Pp-ace1 and Pp-ace2 genes in insect sf9 cells showed high AChE activities. The kinetic parameters, Vmax and Km, of two recombinant AChE proteins were significantly different. The sensitivities to six insecticides were determined in two recombinant AChEs. Pp-AChE1 was more sensitive to all tested insecticides than Pp-AChE2, such as fenobucarb (54 times in Ki ratios), isoprocarb (31 times), carbaryl (13 times) and omethoate (6 times). These results indicated that Pp-AChE1 might be the major synaptic enzyme in the spider. By sequence comparison of P. pseudoannulata and insect AChEs, the key amino acid differences at or close to the functional sites were found. The locations of some key amino acid differences were consistent with the point mutation sites in insect AChEs that were associated with insecticide resistance, such as Phe331 in Pp-AChE2 corresponding to Ser331Phe mutation in Myzus persicae and Aphis gossypii AChE2, which might play important roles in insecticide selectivity between P. pseudoannulata and insect pests. Of course, the direct evidences are needed through further studies.

This study used a cell/microbe co-incubation assay to evaluate the effect of four organophosphorus insecticides (parathion-methyl, azinphos-methyl, omethoate, and methamidophos) metabolized by coriander (Coriandrum sativum). The reverse mutation of Salmonella typhimurium strains TA98 and TA100 was used as an indicator of genetic damage. Treatments with these insecticides inhibited peroxidase activity in plant cells by between 17% (omethoate) and 98% (azinphos-methyl) and decreased plant protein content by between 36% (omethoate) and 99.6% (azinphos-methyl). Azinphos-methyl was the most toxic when applied directly. In the Ames test, treatments applied directly to strain TA100 killed the bacteria; however, the presence of plant metabolism detoxified the system and permitted the growth of bacteria. In strain TA98, plant metabolites of insecticides were mutagenic. This result suggests that the tested pesticides produce mutations through frameshifting. The same pesticides were applied to human skin (HaCaT) and lung (NL-20) cell lines to evaluate their effects on cell viability. Pesticides applied directly were more cytotoxic than the combination of pesticide plus coriander metabolic fraction. Omethoate and methamidophos did not affect the viability of HaCaT cells, but azinphos-methyl and parathion-methyl at 100 and 1000μgmL(-1) significantly decreased viability (p

A novel sensitive visual screening card for rapid detection of pesticide residues was developed based on the blue-green color intensity changes, which were generated as a result of indoxyl acetate hydrolysis catalyzed by acetylcholinesterase (AChE) and the inhibition of AChE activity by pesticides. The procedure for preparing the test card was optimized. The AChE was immobilized onto the Hybond N + nylon membrane using physical adsorption method. The immobilization temperature was set at 4 °C and the immobilization time was set to 30 min. The immobilized enzyme was freeze dried under vacuum conditions for 2 min. The indoxyl acetate was dissolved in methanol and diluted to 10 mM by phosphate buffer solution (pH7.5). The inhibition time and the color development time were set to 15 min and 10 min respectively. The final experimental results on determining various pesticides showed that the limit of detection (LOD) of this assay system was 1 μg/mL for omethoate, 0.1 μg/mL for dichlorvos, 2 μg/mL for methamidophos, 0.05 μg/mL for chlorpyrifos, 1.5 μg/mL for carbaryl, and 0.8 μg/mL for pirimicarb. Detection results of pesticide residues in real food samples of fruit juices and vegetable showed this visual screening card had high sensitivity, good reproducibility and stable-storage property, suggesting its great potential for practical application in rapid determination of pesticide residues.

Pesticides in the inhalable fraction of particulate matter (PM10) should be well tracked in order to contribute information to future exposure assessment in individuals of the general public. A total of 40 current-used pesticides and metabolites were searched for in ambient air samples collected from January through December 2010. The samples were taken from one remote, one urban and three rural sites in Valencia Region (Spain) and analyzed using liquid chromatography coupled to mass spectrometry in tandem (LC-MS/MS). In the PM10 fraction 17 pesticides and metabolites were detected overall, two of them currently banned (carbofuran and omethoate, although the latter is a metabolite of the permitted pesticide dimethoate). The detected pesticides appeared at frequencies ranging from 1 to 75%, with omethoate, terbuthylazine and its metabolites, and carbendazim presenting the highest frequencies. The concentrations detected ranged from few pg m−3 to thousands of pg m−3, with omethoate having the highest average concentration (141.15 pg m−3) in the 5 sites overall. Each station showed its own specific pesticide profile, which is linked to the different types of crops around each site. In the rural stations pesticide levels were greater in spring and early summer, which correlates with their application in agricultural practices. These findings suggest that more efforts are required to implement an extensive air monitoring network in Europe for pesticide control and to develop regulations or recommendations regarding safer pesticide levels in ambient air.

In this study we propose a chromogenic platform for rapid analysis of organophosphate (OP) and carbamate (CM) insecticide residues, based on recombinant Drosophila melanogaster acetylcholinesterase (R- Dm AChE) as enzyme and indoxyl acetate as substrate. The visible chromogenic strip had the advantages identical to those of commonly used lateral flow assays (LFAs) with utmost simplicity in sample loading and result observation. After optimization, depending on the color intensity (CI) values, the well-established assay has the capabilities of both qualitative measurement via naked eyes and quantitative analysis by colorimetric reader with the desirable IC 50 values against the tested six insecticides (0.06 μg mL −1 of carbofuran, 0.28 μg mL −1 of methomyl, 0.03 μg mL −1 of dichlorvos, 31.6 μg mL −1 of methamidophos, 2.0 μg mL −1 of monocrotophos, 6.3 μg mL −1 of omethoate). Acceptable matrix effects and satisfactory detection performance were confirmed by in-parallel LC–MS/MS analysis in different vegetable varieties at various spiked levels of 10 −3 to 10 1 μg g −1 . Overall, the testified suitability and applicability of this novel platform meet the requirements for practical use in food safety management and environmental monitoring, especially in the developing world.

The degree of insecticide resistance, synergism effects, acetylcholinesterase (AChE) activity kinetics, specific activities of detoxification enzymes and cross-resistance were investigated in omethoate resistant and relatively susceptible strains of Aphis gossypii Glover. The resistant cotton aphid strain (ORR) exhibited 231.3-fold resistance to omethoate compared to the susceptible strain (OSS). Synergist piperonyl butoxide (PBO) dramatically increased the toxicity of omethoate in the resistant strain, while triphenyl phosphate (TPP) and diethyl maleate (DEM) did not exhibit synergism effects. The calculated AChE activity, V max and K m ratios of ORR to OSS were 0.1, 0.2 and 0.4, respectively. Based on analysis of IC 50 indices, enzyme inhibition experiments showed that AChE from the ORR strain was 10.6-, 3.2-, 6.2-, 10.5- and 4.4-fold more insensitive to inhibition by eserine, omethoate, paraoxon, paraoxon-methyl and malaoxon, respectively, than that from the OSS strain. The cytochrome P450-mediated O-demethylation activity (3.7-fold) and ethoxycoumarin-O-deethylase activity (2.6-fold) in the ORR strain were significantly higher than in the OSS strain. Specific activity of carboxylesterase (CarE) and glutathione S-transferase (GST) were not significantly different in both the ORR and OSS strains. Bioassay results indicated the ORR strain had developed high levels of cross-resistance to chlorpyrifos (24.2-fold), malathion (21.1-fold), acephate (10.2-fold), esfenvalerate (30.6-fold), methomyl (22.4-fold), carbofuran (33.2-fold), but had negative cross-resistance to bifenthrin (0.4-fold). Overall, these results demonstrate that reduced AChE sensitivity, combined with increased cytochrome P450 monooxygenase detoxification, plays an important role in the high levels of omethoate resistance and can cause cross-resistance to other insecticides in the ORR strain.

Omethoate is one of the most powerful insecticides in China. Despite its high risks of human health and environmental safety, omethoate is still hard to be replaced because of its low price and high efficiency. To better understand physiological and biochemical responses to omethoate, we examined plant growth and antioxidative defense responses as well as omethoate uptake in wheat seedlings grown hydroponically with omethoate. Fresh and dry shoot weights were significantly higher at low concentrations (e.g. 0.1 g/L) than at high concentrations (e.g. 5.0 g/L). The same is true for the soluble protein content. On the contrary, contents of malondialdehyde, proline and omethoate, and activities of superoxide dismutase, peroxidase and ascorbate peroxidase in shoots increased linearly with increasing concentration of omethoate and with exposure time as well. However, catalase activity was increased dramatically at 0.1 g/L but sharply decreased by omethoate added at 1.0 g/L and above compared with that of the control. Taken together, these results support our hypothesis that antioxidative defense response is an important component of plant responses to omethoate and oxidative damage is the major cause for growth reduction of wheat exposed to higher concentrations of omethoate.

In the present study an effort has been made to evaluate the residues of selected insecticides (organophosphorous and pyrethroid) and fungicides (triazoles and chloronitriles) in fruits and vegetables collected from Xiamen, China, during the October 2006 to March 2009 monitoring campaign. Gas chromatography with electron capture detector (GC-ECD) was used to determine the concentrations of 22 pesticide residues among those recommended for pest treatment. Of 1135 samples (37.7%) that contained pesticide residues, pakchoi cabbage, legumes, and leaf mustard were the commodities in which pesticide residues were most frequently detected, with 17.2%, 18.9% and 17.2% of the samples exceeding the maximum residue limits (MRLs), respectively. Concerning the most frequently detected pesticide residues, cypermethrin was found in 18.7% of the samples analyzed. Data obtained were then used for estimating the potential health risks associated with the exposures to these pesticides. The estimated daily intakes (EDIs) range from 0.1% of the ADI for cyfluthrin to 2.61% of the ADI for omethoate and 0.1% of the ADI for omethoate. The most critical commodity is legumes, contributing 2.61% to the hazard index (HI). The results show that despite a high occurrence of pesticide residues in fruits and vegetables from this region, it could not be considered a serious public health problem. Nevertheless, an investigation into continuous monitoring and tighter regulation of pesticide residues in fruits and vegetables is recommended.

Omethoate (OMT), a typical organophosphorus pesticide and also an oxidation byproduct of dimethoate, is very difficult to remove from water due to its hydrophilic nature and relatively low reactivity towards ozone. In this work, Fe(III)-loaded activated carbon (Fe@AC) was prepared and used as catalyst to promote OMT degradation by ozone. The catalytic activity of Fe@AC was investigated under various experiment conditions. Results indicate that the OMT removal was significantly enhanced in O3/Fe@AC through effective generation of hydroxyl radicals (·OH), as compared to ozonation alone and O3/AC. The Fe(III) deposited on AC mainly existed in the form of ferrihydrite (FHD) particles which provided the main active sites promoting ozone decomposition. The optimal pH ranged from 7.0 to 8.0 for catalytic ozonation, which corresponded to a nearly neutral surface charge of the catalyst. The apparent rate constant of OMT degradation was almost linearly correlated with the aqueous ozone concentration. The acute toxicity of the reaction solution was substantially reduced by catalytic ozonation with Fe@AC.

The carmine spider mite Tetranychus cinnabarinus is the most serious of crop mite pests in China. Their ability to rapidly develop resistance to acaricides has caused difficulty in controlling this mite. In this study, the molecular mechanism of acaricide resistance associated with esterase genes TCE1 and TCE2 was investigated in susceptible and acaricide-resistant strains of T. cinnabarinus. The quantitative real-time PCR (qrtPCR) method was adopted to compare the expression level of two esterase genes TCE1 and TCE2 among four different strains (abamectin-resistant, AbR; fenpropathrin-resistant, FeR; omethoate-resistant, OmR and susceptible strains, S) of T. cinnabarinus. The relative expression level of TCE2 was 1.39–2.47 fold in the three resistant strains compared with the S strain. And after inducing with abamectin, fenpropathrin, and omethoate the highest expression level of TCE2 in the S was 1.64-, 2.92- and 2.24-fold compared with the control, respectively, and this difference was found to be significant. However, there was no obvious difference of the mRNA relative expression levels of TCE1 genes among the four strains, and those of TCE1 were not higher than the control throughout the study. Furthermore, the expression modes of TCE1 and TCE2 in AbR and FeR were similar with that in the S after being treated with abamectin and fenpropathrin, respectively. These results indicated that the enhanced expression of esterase gene TCE2 was associated with acaricide-resistance in T. cinnabarinus.

We have investigated surface-enhanced Raman spectroscopy (SERS) spectrum of Omethoate (O,O-dimethyl-S-methylcarbamoylmethylthiophosphate). It is found significant signals in the ordinary Raman spectrum for solid-state Omethoate as well as strong vibrational signals absorbed on the silver sol surface which is prepared by γ-irradiation technique at a very low concentration. Effects of pH and anions (Cl-, Br-, I-) on the adsorption orientation are investigated as well. Two different adsorption mechanisms are deduced, depending on the experimental conditions. The sulfur atom or the sulfur and two oxygen atoms are adsorbed onto the silver sol surface. Among halide ions, Br- and I- are more strongly adsorbed onto the silver sol surface. As a result, the adsorption of Omethoate is less effective due to their steric hindrance.

The degree of insecticide resistance, acetylcholinesterase (AChE) activity kinetics, AChE gene expression and the cDNA sequence of AChE gene were investigated in resistant and relatively susceptible strains of the cotton aphids, Aphis gossypii (Glover). The resistant strain (ORR) exhibited 53.28-fold resistance to omethoate compared to the relatively susceptible strain (OSS) in cotton aphids. AChE activity, V(max) and K(m) were significantly lower in the ORR strain than in the OSS strain (0.13-, 0.04- and 0.31-fold, respectively). Based on analysis of IC(50) indices, enzyme inhibition experiments showed that AChE from the ORR strain was 7.99-, 4.12-, 4.27-, 8.71- and 4.57-fold insensitive to inhibition by eserine, omethoate, paraoxon, paraoxon-methyl and malaoxon than the OSS strain. Sequence analysis indicated that there were no amino acid substitutions in AChEI (Ace1) and AChEII (Ace2) between the OSS and ORR strain. However, when compared with the 81-171B strain (GenBank No. AF502081), we detected two site mutations (S146N and L532P) in Ace1 with high frequency in both the ORR and OSS strains. One conserved mutation (S431F) in Ace2 was also found in both strains when compared with the 171B strain (GenBank No. AJ748114). Measurements of the levels of gene expression for Ace1 and Ace2 in ORR and OSS, as determined by real-time quantitative PCRs, revealed that the relative transcription levels of Ace1 and Ace2 were 0.26- and 1.07-fold, respectively, in the ORR strain as compared to the OSS strain. These results indicate that the altered AChE sensitivity brought about by a decreased transcriptional level of Ace1 mRNA and combined with the site mutants in both Ace1 and Ace2 might be related to omethoate resistance in cotton aphids.

The aim of this work was to investigate whether reduced glutathione (GSH) could protect rats from the respiratory muscle injury induced by omethoate. Three groups named as control, OM (omethoate poisoning) and OM + GSH (omethoate poisoning treated with GSH) were arranged. The cholinesterase (ChE) activity was assayed and the pathological observation of respiratory muscles was carried out. Furthermore, activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and the free organophosphate (FOP) remained in the respiratory muscles were measured. The results indicated that ChE activity was significantly inhibited by omethoate and not be changed by GSH. GSH could attenuate the respiratory muscle injury after omethoate poisoning. No changes of SOD, GPx, CAT and FOP were found after GSH was given. The findings suggested that GSH could protect the respiratory muscle against injury induced by omethoate, which was not the result of GSH to reactivate ChE or regulate the antioxidant enzymes.

Diethylphosphono acetic acid (DPA) was used as a current hapten to generate broad specificity polycolonal antibodies against a group of organophosphorus pesticides. Six New Zealand white rabbits were immunized with immunogens synthesized by the active ester method (AEM) or 1-ethyl-3-(3-dimethylaminopropyl)-carbodimide method (EDC). The titers of antisera reached 25 600 by AEM and 6 400 by EDC, respectively. Polyclonal antibodies raised against DPA were screened and selected for the competitive indirect enzyme-linked immunosorbent assay (CI-ELISA). A CI-ELISA for DPA was developed with a detection limit of 3.536 ng mL−1 and an I50 value of 0.182 μg mL−1. The assay specificity was evaluated by obtaining competitive curves for several structurally related compounds as competitors. The antiserum showed high affinities to chlorpyrifos, diazinon, omethoate, parathion-ethyl and profenofos with I50 of 0.12, 0.15, 0.21, 0.88, 0.97 and 2.5 μg mL−1, respectively. The results indicate that the assay could be a screening tool for quantitation and semi- quantitation determination of the above former five organophosphorus pesticides.

Levels of insecticide resistance, carboxylesterase activity, and carboxylesterase expression were investigated in both omethoate-selected resistant and susceptible strains of cotton aphids, Aphis gossypii (Glover). The resistant strain exhibited 21.72-fold resistance to omethoate based on comparison LC 50 values with the susceptible strain in cotton aphids. Five substrates, α-naphthyl acetate (α-NA), β-naphthyl acetate (β-NA), α-naphthyl butyrate (α-NB), α-Naphthyl propionate (α-NPr), and α-naphthyl phosphate (α-NP) were used to determine carboxylesterase activity in both resistant and susceptible strains of cotton aphids. Carboxylesterase activity was significantly higher in resistant strain than in susceptible strain, 11-fold for α-NA and β-NA, 12-fold for α-NB and 10-fold for α-NPr and α-NP. The levels of gene expression for carboxylesterase of both resistant and susceptible strains were determined by real-time quantitative PCRs. Compared with the susceptible strain, the relative transcription levels and gene copy numbers of the carboxylesterase were 4.54- and 0.97-fold in the resistant strain, respectively. These results indicated that the increased expression of the carboxylesterase resulted from the increased transcription levels of carboxylesterase mRNA was related to omethoate resistance in cotton aphids.

Dimethoate (DIM) is an organophosphorothionate (OPT) pesticide used worldwide as a systemic insecticide and acaricide. It is characterized by low-to-moderate acute mammalian toxicity; similarly to the other OPT pesticides, its mode of action is mediated by the inhibition of acetylcholinesterase (AChE), exerted by its toxic metabolite dimethoate-oxon or omethoate (OME), which is also used as a direct acting pesticide. Human hepatic DIM bioactivation to the toxic metabolite OME has been characterized by using c-DNA expressed human CYPs and human liver microsomes (HLM) also in the presence of CYP-specific chemical inhibitors, with a method based on AChE inhibition. The obtained kinetic parameters and AChE IC(50) have been compared with those previously obtained with other OPTs, indicating a lower efficiency in DIM desulfuration reaction and a lower potency in inhibiting AChE. Results showed that, similarly to the other OPTs tested so far, at low DIM concentration OME formation is mainly catalysed by CYP1A2, while the role of 3A4 is relevant at high DIM levels. Differently from the other OPTs, DIM desulfuration reaction showed an atypical kinetic profile, likely due to CYP3A4 autoactivation. The sigmoidicity degree of the activity curve increased with the level of CYP3A4 in HLM or disappeared in the presence of a CYP3A4 chemical inhibitor. This atypical kinetic behaviour can be considered one of the possible explanations for the recent findings that among patients hospitalized following OPT intoxication, DIM ingestion gave different symptoms and more severe poisoning (23.1% of fatal cases versus total) than chlorpyrifos (8% of deaths), which has a lower LD(50) value. Since DIM-poisoned patients poorly responded to pralidoxime, the possibility to use CYP3A4 inhibitors could be considered as a complementary treatment.

Wheat aphid, Sitobion avenae (fabricius), is one of the most important wheat pests and has been reported to be resistant to commonly used insecticides in China. To determine the resistance mechanism, the resistant and susceptible strains were developed in laboratory and comparably studied. A bioassay revealed that the resistant strain showed high resistance to pirimicarb (RR: 161.8), moderate reistance to omethoate (32.5) and monocrotophos (33.5), and low resistance to deltamethrin (6.3) and thiodicarb (5.5). A biochemistry analysis showed that both strains had similar glutathione- S -transferase (GST) activity, but the resistant strain had 3.8-fold higher esterase activity, and its AChE was insensitive to this treatment. The I 50 increased by 25.8-, 10.7-, and 10.4-folds for pirimicarb, omethoate, and monocrotophos, respectively, demonstrating that GST had not been involved in the resistance of S. avenae . The enhanced esterase contributed to low level resistance to all the insecticides tested, whereas higher resistance to pirimicarb, omethoate, and monocrotophos mainly depended on AChE insensitivity. However, the AChE of the resistant strain was still sensitive to thiodicarb (1.7-fold). Thus, thiodicarb could be used as substitute for control of the resistant S. avenae in this case. Furthermore, the two different AChE genes cloned from different resistant and susceptible individuals were also compared. Two mutations, L436(336)S in Sa.Ace1 and W516(435)R in Sa.Ace2, were found consistently associated with the insensitivity of AChE. They were thought to be the possible resistance mutations, but further work is needed to confirm this hypothesis.

On the basis of several experiments carried out in China, it was proved that both seaweed liquid fertilizer and rare earth (RE) could promote the growth of crops and increase their yield. The effects of extraction from seaweed and its complex with RE on the degradation of organophosphorous pesticides and the yield of vegetables were investigated. The results showed that the extract and its complex with RE could degrade organophosphorous pesticides in neutral solvent. The residues of the pesticides treated by the extract decreased by 96.88%, 52.30%, 49.52%, and 22.88%, respectively, for chlorpyrifos, dichlorvos, omethoate, and dimethoate, and those by the complex decreased by 95.99%, 54.23%, 48.79%, and 25.66%, respectively, when compared with the control. The residues of chlorpyrifos and dimethoate in spinach sprayed with the complex were decreased by 90.64% and 76.56%, respectively, compared with those in spinach from control plots when the interval between spraying and sampling was 8 d. The fresh weight of brassica chinensis and cabbage increased by 28.62% and 18.72%, and their dry weight increased by 44.49% and 14.74%, respectively, compared with those of the controls. The chlorpyrifos and dimethoate residues in brasscia chinese were decreased by 36.36% and 50.00%, respectively, and their rate of decrease in cabbage was 40.00% and 75.00%, respectively, on 5th day after spraying with the complex, when compared with those in the vegetable from control. These results suggest that this complex can increase the agricultural productivity and reduce the use of pesticide residues in the production of vegetables.

Resins of complexes made from agarose-Ce4+ (RCA-Ce) and chitosan-Ce4+ (RCC-Ce) were prepared. Hydrolysis rates of methamidophos, omethoate and chlorpyrifos treated by RCA-Ce were 32.39%, 27.12% and 46.62%, respectively, those of chlorpyrifos and methamidophos in mung bean sprout juice 38.28% and 35.45%, and that of chlorpyrifos in tea extract 59.76%. Hydrolysis rates of protein in tea extract treated by RCA-Ce increased by 86.46%. RCC-Ce could be employed in the apple juice production. The contents of methamidophos and parathion-methyl in the juice treated by RCC-Ce decreased 58.76% and 71.92%. Furthermore, RCC-Ce was used to clarification for beer by the ways of a column. RCC-Ce could hydrolyze sensitive protein and increase contents of free amino acid in the beer. Therefore, the beer treated by RCC-Ce could stay oxidation and aging procedure due to some metal ions being absorbed by RCC-Ce.

This work is focused on the effectiveness of headspace solid-phase microextraction (HS-SPME) for the analysis of nine organophosphorus (OPs) insecticides (dimethoate, diazinon, fenitrothion, malathion, fenthion, parathion ethyl, methyl bromophos, methidathion, ethion) and four metabolites (omethoate, malaoxon, fenthion sulfoxide and fenthion sulfone) residues in olive oil samples. The efficiency of six fibre types with different film thickness was compared. PDMS (100 mu m) was found to be the most suitable fibre for the analysis of OPs in olive oils. Optimization of SPME conditions (stirring rate, extraction time, temperature, salt addition) was based on previous developed method in the laboratory that was enriched with additional analytes including major metabolites. In addition, the effect of the oil matrix on the pesticide recoveries was evaluated using spiked oil samples of different composition (acidity, fatty acids, triglycerides, sterols). It was found that only acidity and total amount of sterols are the main factors influencing the SPME efficiency. Matrix effects were compensated for, by using the internal standard method for the quantification of pesticides. The recoveries at three spiking levels were between 80% and 106% with R.S.D. (%) values below 10% in most cases. Good linearity (R-2 > 0.985) was observed in the 0.025-0.50 mg kg(-1) concentration range with satisfactory R.S.D. (%) values of 4.5-10.4%. The method allowed detection of the tested compounds at concentrations below 0.010 mg kg(-1) with GC-FTD detection. In addition, intra- and inter-day precision was satisfactory (R.S.D. (%) < 10%). The performance results confirm the usefulness of the proposed methodology for the analysis of OPs in olive oils. Moreover, the maximum residue limits required by European and international regulations can be attained without difficulty. Finally, the method was applied to 30 virgin olive oil samples from major olive production areas of Greece in the framework of an extended monitoring survey of OPs residues in olive oil. The most commonly found pesticides were fenthion, dimethoate and ethion in levels that did not exceed the MRLs. (c) 2006 Elsevier B.V. All rights reserved. Analytica Chimica Acta

This work presents an automatic method able to identify the presence of neurotoxic insecticides using omethoate as a model compound. The acetylcholinesterase (AChE)-based biosensors used to detect the neurotoxic insecticides present two shortcomings: the weak limit of detection (LOD) and the lack of selectivity. An appropriate LOD is obtained in our work by using two sensitive AChEs from Drosophila melanogaster ( Dm ): the wild type (wt- Dm ) and the E69W mutant. To discriminate between the insecticides and all other interferences, we use a FIA system that provides analytical information acquired from two enzymes: (i) the sensitive Dm- AChEs and (ii) an omethoate-resistant AChE from Electric Eel (Eel), which is equally affected by the matrix. The enzymes were immobilised on screen-printed electrodes by entrapment in a photocrosslinkable PVA-SbQ polymer used with a FIA system with three channels, each one of them simultaneously analysing the same sample using biosensors based on different AChEs. The biosensor based on the wt- Dm had a LOD of 2 × 10 −6 M omethoate, while the one based on the E69W mutant permitted to lower the LOD to 1 × 10 −7 M. Interferences produced by mercury and hypocloryte were successfully discriminated. Environmental water samples were also analysed.

The acute toxicities of two organophosphorodithioate (dimethoate and disulfoton) and two organophosphorothioate (omethoate and demeton-S-methyl) insecticides were evaluated individually and in binary combination with the herbicide atrazine using fourth-instar larvae of the aquatic midge, Chironomus tentans. Atrazine alone up to 1000 μg/L did not show significant toxicity to the midges in a 48-h bioassay. However, atrazine concentrations as low as 1 μg/L in combination with dimethoate at EC25 (concentration to affect 25% of tested midges), 100 μg/L in combination with disulfoton (EC25), and 10 μg/L in combination with demeton-S-methyl (EC25) significantly enhanced the toxicity of each organophosphate insecticide. In contrast, atrazine concentrations of 10 μg/L and above in combination with omethoate (EC25) significantly decreased the toxicity of the insecticide. Biochemical analysis indicated that increased toxicity of dimethoate, disulfoton, and demeton-S-methyl in binary combination with atrazine correlated to the increased inhibition of acetylcholinesterase. Furthermore, cytochrome P450-dependent O-deethylation activity in the midges exposed to atrazine at 1000 μg/L was 1.5-fold higher than that in the control midges. Thus, atrazine appeared to induce cytochrome P450 monooxygenases in the midges. Elevated cytochrome P450 monooxygenase activity may increase the toxicities of dimethoate, disulfoton, and demeton-S-methyl by enhancing the oxidative activation of dimethoate into omethoate, and disulfoton and demeton-S-methyl into their sulfoxide analogs with increased anticholinesterase activity. In contrast, atrazine reduced the toxicity of omethoate possibly by enhancing the oxidative metabolic detoxification since omethoate does not require oxidative activation.

In greenhouse (Khartoum, Sudan), the effect of NeemAzal-T/S® (NA, at 20 g a. i. ha −1 ) on mortality of third instar nymphs of Jacobiasca lybica was not significantly different from that of Omethoate at 200 g a. i. ha −1 . Neem oil (at 0.2 g a. i. ha −1 ) was less effective. In two semi-field tests, numbers of J. lybica and potato yield were negatively correlated. The percentage yield losses were equal in both years. Two field experiments conducted in potato, using a VLV-technique with weekly treatments of 20 l ha −1 , showed similar mortality by NA and fenvalerate (20% EC at 140 g a. i. ha −1 ) in J. lybica and Bemisia tabaci . In Aphis gossypii , fenvalerate exerted a stronger effect (84%) than NA (77%). Potato yield was highest in NA and fenvalerate, lower in neem kernel water extract (NKWE; with 2–5 g a. i. ha −1 ), and equal to water treatment in neem oil (NO). In three similar field experiments in eggplant (aubergines), fenvalerate reduced J. lybica , B. tabaci and A. gossypii by 92%, 70% and 82%, respectively, followed by NA (86%, 61% and 78%). NO and NKWE were less effective. Eggplant yield was highest following NA-treatment, fenvalerate having a lower yield in one of the experiments. NO and NKWE increased the yield in only one of the three experiments. In eggplant, the frequency of stenophagous antagonists of the homopterous pests was affected negatively by fenvalerate, resulting in an unfavourable prey/predator ratio. The neem preparations induced only mild reduction of the antagonists, producing a favourable prey/predator ratio. Based on availability, the effects on pests, beneficials, and on yield, the use of NKWE may be recommended for plant protection in vegetables in the Sudan. Optimal concentrations, in excess of 2–5 g a. i. ha −1 , as used here, and new formulations remain to be studied.

Seventeen organic phosphorus pesticides (OPs) and 18 organic chlorine pesticides (OCs) at water from Jiulong River Estuary (JLRE) are determined by SPE–GC–(FPD and μECD). The contents of the total OPs (17) ranged from 134.8 to 354.6 ng/l (the mean is 227.2 ng/l). Total OCs concentrations varied from 115.4 to 414.7 ng/l in water (mean 237.7 ng/l). The levels of total hexachlorocyclohexane in water varied from 31.95 to 129.8 ng/l (mean 62.51 ng/l), and those of total DDTs were in the range 19.24–96.64 ng/l (mean 48.69 ng/l). The distribution and behavior characteristics of OPs indicate that five main OPs (methamidophos, dichlorvos, malathion, omethoate and dimethoate) occupied the most part of the total OPs, in addition, the sources of the OPs (mainly from current usage) are not stable. While the OCs mainly came from early application and were more stable. The OPs did not have obvious correlation with the dissoved organic carbon and suspended particulate matter at water from JLRE. It maybe due to the complicated hydrological kinetics in the estuary, and the higher water solubility and weak absorption (with organic matter) action of OPs. When compared with other areas, the OPs and OCs level in JLRE are some moderate.