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[Display omitted] • Nitrogen-doped carbon quantum dot (N-CQDs) designed for detection of methiocarb. • Fluorescent-paper sensor with smartphone is exploited for analysis of methiocarb. • Detection of methiocarb is based on quenching of fluorescence intensity of N-CQDs. • Fluorescent-paper sensor is instrument free, portable, user-friendly and rapid. The increasing use of pesticides in the agriculture fields strengthen the crop production to meet the needs of increasing population. The residues in water and food materials cause several health hazards. Herein, nitrogen-doped carbon quantum dot (N-CQDs) is designed for determination of methiocarb pesticide in vegetables by fluorescent paper sensor and compared the results with fluorimetry. The fluorescent paper-based detection is performed by recording the change in fluorescence of N-CQDs with introduction of methiocarb using smartphone and ImageJ software. Good linear range was acquired for analysis of methiocarb from 10 to 1000 μgL−1 with a low detection limit (LOD) of 3.5 μgL−1 in fluorimetry; and 700–10,000 μgL−1 with a LOD of 500 μgL−1 in fluorescent paper sensor. A better recovery from 92.0 to 95.4% illustrating the selectivity of both methods for analysis of methiocarb in vegetables. Thus, the advantage of using N-CQDs as a fluorescent sensor for analysis of methiocarb in vegetables is instrument free, portable and user-friendly. [ABSTRACT FROM AUTHOR]

Despite the high toxicity and resistance to conventional water treatments exhibited by methiocarb (MC), there are no reports regarding the degradation of this priority pesticide by means of alternative purification technologies. In this work, the removal of MC by means of ozonation was studied for the first time, employing a multi-reactor methodology and neutral pH conditions. The second-order rate constants of MC reaction with molecular ozone (O 3 ) and formed hydroxyl radicals (OH·) were determined to be 1.7·10 6 and 8.2·10 9 M −1 s −1 , respectively. During degradation experiments, direct ozone reaction was observed to effectively remove MC, but not its formed intermediates, whereas OH· could oxidize all species. The major identified TPs were methiocarb sulfoxide (MCX), methiocarb sulfoxide phenol (MCXP) and methiocarb sulfone phenol (MCNP), all of them formed through MC oxidation by O 3 or OH· in combination with hydrolysis. A toxicity assessment evidenced a strong dependence on MCX concentration, even at very low values. Despite the OH· capability to degrade MC and its main metabolites, the relative resistance of TPs towards ozone attack enlarged the oxidant dosage (2.5 mg O 3 /mg DOC) necessary to achieve a relatively low toxicity of the medium. Even though ozonation could be a suitable technique for MC removal from water compartments, strategies aimed to further promote the indirect contribution of hydroxyl radicals during this process should be explored. [ABSTRACT FROM AUTHOR]

A simultaneous analytical method was developed for the determination of methiocarb and its metabolites, methiocarb sulfoxide and methiocarb sulfone, in five livestock products (chicken, pork, beef, table egg, and milk) using liquid chromatography–tandem mass spectrometry. Due to the rapid degradation of methiocarb and its metabolites, a quick sample preparation method was developed using acetonitrile and salts followed by purification via dispersive- solid phase extraction (d-SPE). Seven-point calibration curves were constructed separately in each matrix, and good linearity was observed in each matrix-matched calibration curve with a coefficient of determination ( R 2 ) ≥ 0.991. The limits of detection and quantification were 0.0016 and 0.005 mg/kg, respectively, for all tested analytes in various matrices. The method was validated in triplicate at three fortification levels (equivalent to 1, 2, and 10 times the limit of quantification) with a recovery rate ranging between 76.4–118.0% and a relative standard deviation ≤ 10.0%. The developed method was successfully applied to market samples, and no residues of methiocarb and/or its metabolites were observed in the tested samples. In sum, this method can be applied for the routine analysis of methiocarb and its metabolites in foods of animal origins. [ABSTRACT FROM AUTHOR]

• Immobilisation of human FMO1 on glassy carbon electrode with cation surfactant DDAB. • Contact angle and AFM surface measurements of graphene oxide-DDAB. • Enhanced electrochemical signal of FMO1 in presence of graphene oxide. • FMO1 bioelectrode activity towards pesticides; phorate, methiocarb and fenthion. • Successful tandem oxidation of phorate with FMO1 and CYP3A4 bioelectrodes. It is highly advantageous to devise an in vitro platform that can predict the complexity of an in vivo system. The first step of this process is the identification of a xenobiotic whose monooxygenation is carried out by two sequential enzymatic reactions. Pesticides are a good model for this type of tandem reactions since in specific cases they are initially metabolised by human flavin-containing monooxygenase 1 (hFMO1), followed by cytochrome P450 (CYP). To assess the feasibility of such an in vitro platform, hFMO1 is immobilised on glassy carbon electrodes modified with graphene oxide (GO) and cationic surfactant didecyldimethylammonium bromide (DDAB). UV–vis, contact angle and AFM measurements support the effective decoration of the GO sheets by DDAB which appear as 3 nm thick structures. hFMO1 activity on the bioelectrode versus three pesticides; fenthion, methiocarb and phorate, lead to the expected sulfoxide products with K M values of 29.5 ± 5.1, 38.4 ± 7.5, 29.6 ± 4.1 µM, respectively. Moreover, phorate is subsequently tested in a tandem system with hFMO1 and CYP3A4 resulting in both phorate sulfoxide as well as phoratoxon sulfoxide. The data demonstrate the feasibility of using bioelectrochemical platforms to mimic the complex metabolic reactions of xenobiotics within the human body. [ABSTRACT FROM AUTHOR]

The overuse of pesticides to increase essential food production adversely affects the environment and human health. Methiocarb (MTC) is the most effective insecticide (acaricide) for controlling mollusks in soil and plants. However, MTC has poisoning effects on non-targeted living organisms and soil. Therefore, MTC monitoring in soil and water samples is necessary to mitigate its poisoning effect on living organisms. In this study, we explored novel architectures of barium vanadate multi-layered graphene (BaV 2 O 6 -ML-Gr) nanocomposites as highly selective and sensitive electrodes for MTC detection. These materials were synthesized using a facile precipitation method and ultrasonication. They were then utilized as electrode matrices for the electrochemical quantification of MTC in environmental samples. Subsequently, the electrochemical performance of the BaV 2 O 6 -ML-Gr/screen-printed carbon electrode (SPCE) was evaluated using differential pulse voltammetry, which revealed a high sensitivity of 1.0805 µA/(µM−1 cm−2) with a low detection limit of 8 nM and an adequate linear response of 0.01–64.9 µM. The real-time quantification of MTC using BaV 2 O 6 -ML-Gr/SPCE was conducted with different soil and water samples, which provided acceptable recovery results for MTC. The results showed that BaV 2 O 6 -ML-Gr/SPCE can be used for the on-site electrochemical analysis of MTC. • We prepared a BaV 2 O 6 -ML-Gr nanocomposite via co-precipitation and sonication. • Novel architecture BaV 2 O 6 -ML-Gr/SPCE was used for electrochemical detection of MTC. • BaV 2 O 6 -ML-Gr/SPCE exhibits an adequate linear range and lower LOD. • The BaV 2 O 6 -ML-Gr/SPCE provides an excellent sensing ability to the MTC in different soil and water samples. [ABSTRACT FROM AUTHOR]

The application of molluscicides baits on the soil surface is the most common practice to control terrestrial gastropods. There seems to be a gap in the accurate evaluation of molluscicidal baits effects to soil arthropods, since their hazard to non-target organisms has been considered low after mixing baits into soil. In this work the ecotoxicological effects of two molluscicide baits (metaldehyde and methiocarb) to the collembolan Folsomia candida were evaluated using two different approaches: (1) molluscicidal baits were applied to the top soil once and only at the beginning of the exposure and avoidance behaviour and reproduction were evaluated; and (2) baits were replaced by new ones after 14-d of exposure, simulating the recommended application rate recommended by the manufacturer and reproduction was assessed (repeated/pulse exposure). A preference for the side contaminated for methiocarb was observed but the distribution of collembolans in the avoidance test with metaldehyde was random. Exposure to metaldehyde resulted in a significant increase in mortality. For methiocarb, a reduction in the juveniles produced but no acute effects were observed. In the bait pulse test, the toxic effects of each chemical was significantly increased compared with the single exposure test, for all treatments used (both reproduction and mortality). In summary, molluscicides have an adverse effect on F. candida , with severe effects on their behaviour (only for methiocarb), reproduction and survival (for both), which can lead to population collapse with time. [ABSTRACT FROM AUTHOR]

Abstract: The micropollution of drinking water sources with pesticides has become a global concern. This work investigated the degradation of methiocarb (MC), a most commonly-used carbamate pesticide, by monochloramine (NH2Cl) under simulated water treatment conditions. Results indicate that the reaction was of first-order in MC and varied orders in NH2Cl depending on water pH. The observed rate constant of MC degradation decreased quickly with either a decrease in the molar ratio of chlorine to ammonia (Cl2:N) or an increase in water pH. The apparent activation energy of the reaction was determined to be 34 kJ mol−1. The MC degradation pathways also exhibited a strong pH dependence: at pH 6.5, MC was first oxidized by NH2Cl to methiocarb sulfoxide (MCX), and then hydrolyzed to methiocarb sulfoxide phenol (MCXP); while at pH 8.5, MCX, MCXP and methiocarb sulfone phenol (MCNP) were formed successively through either oxidation or hydrolysis reactions. Based on the identified byproducts and their concentrations evolution, the proposed pathways of MC degradation in the presence of NH2Cl were further validated through kinetic model simulations. [Copyright &y& Elsevier]

Highlights: [•] A stoichiometric ratio of 1:1 was determined for MC reacting with free chlorine. [•] MC reacted with free chlorine at an intrinsic rate constant of 2.42×108 M−1 s−1. [•] MCX and MCN were identified as the major degradation byproducts. [•] The further degradation of MCX to MCN (or MCXP) was highly pH dependent. [•] The toxicity of MC solution increased obviously after chlorination. [ABSTRACT FROM AUTHOR]

Abstract: The characteristics of host–guest complexation between tetrabutyl ether derivatives of p-sulfonatocalix[4]arene (SC4Bu) and methiocarb [3,5-dimethyl-4-(methylthio) phenyl methylcarbamate] were investigated by fluorescence spectrometry. Upon addition of methiocarb, the fluorescence intensity of SC4Bu was quenched regularly and a slight red shift was observed for the maximum emission peak. These results indicated that the SC4Bu-methiocarb complex was formed a 1:1 mole ratio. An association constant of 1.67×104 Lmol−1 was calculated by applying a deduced equation. The interaction mechanism of the inclusion complex was discussed. Based on the results, a novel spectrofluorimetric method was described for the determination of methiocarb with a detection limit at 0.05μgmL−1. This method is very simple and shows high sensitivity and selectivity. Moreover, the proposed method was successfully applied to the determination of methiocarb in water samples. [Copyright &y& Elsevier]

Abstract: Earthworms are important organisms for the soil ecosystem. They are sensitive to toxic chemicals and represent useful bioindicator organisms for soil biomonitoring. Recently the use of biomarkers in earthworms has been increasingly investigated for soil monitoring and assessment purpose. The aim of the preset paper was to analyze the pollutant-induced response of a suite of cellular and biochemical biomarkers in the earthworm Lumbricus terrestris exposed to copper sulphate or methiocarb in OECD soil at the maximal concentrations recommended in agriculture. These responses were compared to lifecycle parameters such as survival, growth and reproduction. Granulocyte morphometric alteration, lysosomal membrane stability, metallothionein concentration, and acetylcholinesterase activity were considered. In either copper sulphate or methiocarb exposure conditions the mean percentage variation of the pollutant-induced molecular and cellular biomarkers was consistent with the whole organism end-point responses. In particular pollutant-induced granulocyte enlargement, detected in either copper sulphate or methiocarb exposed organisms, showed to be a potential general biomarker that may be directly linked to organism health. Compared to the other biological responses to pollutants, it showed high sensitivity to pollutant exposure suggesting its possible applications as a sensitive, simple, and quick general biomarker for monitoring and assessment applications. [Copyright &y& Elsevier]

Abstract: We learned previously that red-winged blackbirds (Agelaius phoeniceus) use affective processes to shift flavor preference, and cognitive associations (colors) to avoid food, subsequent to avoidance conditioning. We conducted three experiments with captive red-winged blackbirds to reconcile varied consequences of treated food with conditioned sensory cues. In Experiment 1, we compared food avoidance conditioned with lithium chloride (LiCl) or naloxone hydrochloride (NHCl) to evaluate cue–consequence specificity. All blackbirds conditioned with LiCl (gastrointestinal toxin) avoided the color (red) and flavor (NaCl) of food experienced during conditioning; birds conditioned with NHCl (opioid antagonist) avoided only the color (not the flavor) of food subsequent to conditioning. In Experiment 2, we conditioned experimentally naïve blackbirds using free choice of colored (red) and flavored (NaCl) food paired with an anthraquinone- (postingestive, cathartic purgative), methiocarb- (postingestive, cholinesterase inhibitor), or methyl anthranilate-based repellent (preingestive, trigeminal irritant). Birds conditioned with the postingestive repellents avoided the color and flavor of foods experienced during conditioning; methyl anthranilate conditioned only color (not flavor) avoidance. In Experiment 3, we used a third group of blackbirds to evaluate effects of novel comparison cues (blue, citric acid) subsequent to conditioning with red and NaCl paired with anthraquinone or methiocarb. Birds conditioned with the postingestive repellents did not avoid conditioned color or flavor cues when novel comparison cues were presented during the test. Thus, blackbirds cognitively associate pre- and postingestive consequences with visual cues, and reliably integrate visual and gustatory experience with postingestive consequences to procure nutrients and avoid toxins. [ABSTRACT FROM AUTHOR]

Abstract: The kinetics and mechanism for methiocarb (MC) degradation by aqueous ClO2 were investigated under simulated water treatment conditions. Experimental results indicate that the reaction between MC and ClO2 was of second-order overall, and the rate constant rapidly increased from 0.56 to 4.5M−1 s−1 as the solution pH increased from 6.0 to 9.1 at 23°C. The activation energy was determined to be 75kJmol−1 in the studied temperature range of 7–35°C. Methiocarb sulfoxide (MCX) and methiocarb sulfone (MCN) were quantified to be the major byproducts from MC degradation. Unlike the sequential formation of sulfoxide and sulfone during the oxidation of many thioethers, the two byproducts were formed simultaneously during MC degradation by ClO2. The solution pH significantly affected the type and quantity of the degradation byproducts. For example, at pH 6.5 MCX and MCN accumulated as the reaction proceeded and finally accounted for 71% and 28% of MC degraded, respectively; while at pH 8.6 three more minor byproducts were identified. Though ClO2 can effectively oxidize MC in water, the significant increase in toxicity raises a potential risk to consumers. [Copyright &y& Elsevier]

Abstract: A simple and rapid immunochromatographic assay for a sensitive and inexpensive monitoring of methiocarb in surface water was developed using a binding inhibition format on a membrane strip. In the assay, detection reagent consisted of anti-methiocarb antibody and colloidal carbon-labelled secondary antibody. Methiocarb-ovalbumin conjugate was immobilized in a test line of the strip as a capture reagent. Colour intensity of the test line in methiocarb-positive assay was visually distinguishable from that of negative sample within 10min. The optimized semi-quantitative method provided a visual detection limit of 0.5ngmL−1. Cross-reactions with other carbamate pesticides were not found (<1%). Only a negligible matrix effect of surface water was recognized. In parallel analyses of spiked water samples, the assay results were in a good agreement with those of ELISA. The stability test indicated the strips could be used at least 2 months without change in performance. All characteristics of the visually evaluated assay mentioned above were verified by instrumental quantification of colour intensity in test lines. The developed immunochromatographic assay offers potential as a useful on-site screening tool for environmental analysis. [Copyright &y& Elsevier]

Abstract: Methiocarb, is used worldwide in agriculture and health programs. Besides its advantages in the agriculture, it causes several toxic effects. In this study, we aimed to investigate subacute effects of methiocarb on lipid peroxidation, reduced glutathione (GSH), antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and glutathione reductase (GSH-Rd) and histopathological changes in rat tissues. Moreover, we examined the possible protective effects of vitamin E and taurine on methiocarb-induced oxidative damage in rat tissues. Rats were randomly divided into six groups as follows; I-control group; II-methiocarb group; III-vitamin E group; IV-vitamin E+methiocarb group; V-taurine group and VI-taurine+methiocarb group. Methiocarb significantly increased lipid peroxidation in liver and kidney when compared to control groups. Levels of GSH and activities of SOD, CAT and GSH-Px were found to be decreased, while GSH-Rd remained unchanged in rat liver and kidney treated with methiocarb. Pretreatment of vitamin E and taurine resulted in a significant decrease on lipid peroxidation, alleviating effects on GSH and antioxidant enzymes. The degenerative histological changes were less in liver than kidney of rats treated with methiocarb. Pretreatment of vitamin E and taurine showed a protective effect on the histological changes in kidney comparing to the liver of rats treated with methiocarb. [Copyright &y& Elsevier]

Abstract: Although the ecological risks of toxic chemicals are usually assessed on the basis of individual responses, such as survival, reproduction or growth, ecotoxicologists are now attempting to assess the impact of environmental pollution on the dynamics of naturally exposed populations. The main issue is how to infer the likely impact on the population of the toxic effects observed at the individual level. Dynamic energy budget in toxicology (DEBtox) is the most user-friendly software currently available to analyze the experimental data obtained in toxicity tests performed on individuals. Because toxic effects are diverse and because the sensitivity of individuals varies considerably depending on life-cycle stage, Leslie models offer a convenient way of predicting toxicant effects on population dynamics. In the present study, we first show how parameter inputs, estimated from individual data using DEBtox, can be coupled using a Leslie matrix population model. Then, using experimental data obtained with Chironomus riparius, we show how the effects of a pesticide (methiocarb) on the population growth rate of a laboratory population can be estimated. Lastly, we perform a complex sensitivity analysis to pinpoint critical age classes within the population for the purposes of the field management of populations. [Copyright &y& Elsevier]

The electrooxidation of methiocarb and bisphenol A was studied in complex matrices, namely, simulated and real sanitary landfill leachate samples, using a boron-doped diamond anode. With simulated sanitary landfill leachate samples, the influence of the type and ratio of carbon source (glucose/humic acid) and electrolyte (NaCl or Na 2 SO 4) on the emerging contaminants removal was assessed. Using real sanitary landfill leachate, the influence of current density was evaluated. The experimental results showed that electrooxidation, using a boron-doped diamond anode, can be successfully utilized to degrade methiocarb and bisphenol A when present in complex matrices, such as sanitary landfill leachate, and that methiocarb is more easily oxidized than bisphenol A. Furthermore, it was found that the presence of chloride and high humic acid content increases emerging contaminants removal rate, showing that electrooxidation at boron-doped diamond is particularly adequate to solve the problems raised by sanitary landfill leachate, even when contaminated with emerging contaminants. Unlabelled Image • Methiocarb, watch list priority substance, is completely degraded by electrooxidation. • Methiocarb is more easily oxidized than bisphenol A. • The presence of chloride increases methiocarb and bisphenol A removal rates. • The increase in humic acid content leads to higher methiocarb and BPA removals. • Electrooxidation can successfully degrade methiocarb and BPA in landfill leachates. [ABSTRACT FROM AUTHOR]

Abstract: Previous studies have shown that seed dressing with methiocarb or metaldehyde can protect newly emerged oilseed rape seedlings from slug damage. Here, we document two mini-plot field experiments testing these seed dressings. Both metaldehyde and methiocarb significantly reduced slug damage compared with untreated control seeds, but both seed dressings performed less well to the metaldehyde bait pellets. Protection offered by metaldehyde seed dressing was short-lived, whereas methiocarb seed dressings gave protection throughout the 4 weeks duration of both experiments. [Copyright &y& Elsevier]