Environmental fate and metabolic transformation of two non-ionic pesticides in soil: Effect of biochar, moisture, and soil sterilization.

Soil moisture, organic matter, and soil microbes are the key considering factors that control the persistence, degradation, and transformation of applied pesticides under varied soil conditions. In this study, underlying influence of these factors was assessed through the fates and metabolic transformation of two non-ionic pesticides (e.g., Phorate and Terbufos) in soils. Concisely, two distinct experiments including a customized batch equilibrium (sorption study), and a lab incubation trial (degradation study) were performed, following the OECD guidelines. As per study findings, biochar (BC) amendment was found to be the most influential factors during sorption study, particularly, 1% BC amendment contributed to achieve the best results. In addition, the non-linearity of sorption isotherm (1/n < 1.0) was revealed through Freundlich isotherm, indicating the strong adsorption of studied pesticides onto the soils. On the other hand, during degradation study, soil moisture initiates the enhanced degradation of parent pesticides and subsequent metabolism. In the presence of 40% water holding capacity (WHC), 1% BC amendment enhances the metabolic transformation, while H2O2 treatment could hinder the process. Additionally, the half-life degradation (t1/2) of phorate and terbufos was controlled by biochar amendment, moisture, and soil sterilization, respectively. Finally, BC can accelerate the metabolic transformation, whereas, phorate underwent a metabolic change into sulfoxide and sulfone while terbufos turned into solely sulfoxide. This pioneering study gathered crucial data for understanding the persistence and metabolic transition of non-ionic pesticides in soils and their patterns of degradation.

Highly Sensitive Fluorescence Detection of Three Organophosphorus Pesticides Based on Highly Bright DNA-Templated Silver Nanoclusters.

It is still challenging to achieve simultaneous and sensitive detection of multiple organophosphorus pesticides (OPs). Herein, we optimized the ssDNA templates for the synthesis of silver nanoclusters (Ag NCs). For the first time, we found that the fluorescence intensity of T base-extended DNA-templated Ag NCs was over three times higher than the original C-riched DNA-templated Ag NCs. Moreover, a "turn-off" fluorescence sensor based on the brightest DNA-Ag NCs was constructed for the sensitive detection of dimethoate, ethion and phorate. Under strong alkaline conditions, the P-S bonds in three pesticides were broken, and the corresponding hydrolysates were obtained. The sulfhydryl groups in the hydrolyzed products formed Ag-S bonds with the silver atoms on the surface of Ag NCs, which resulted in the aggregation of Ag NCs, following the fluorescence quenching. The fluorescence sensor showed that the linear ranges were 0.1-4 ng/mL for dimethoate with a limit of detection (LOD) of 0.05 ng/mL, 0.3-2 µg/mL for ethion with a LOD of 30 ng/mL, and 0.03-0.25 µg/mL for phorate with a LOD of 3 ng/mL. Moreover, the developed method was successfully applied to the detection of dimethoate, ethion and phorate in lake water samples, indicating a potential application in OP detection.

Bioelectrochemical platform with human monooxygenases: FMO1 and CYP3A4 tandem reactions with phorate.

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 KM 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.

Protection of Potatoes and Mortality of Wireworms (Agriotes obscurus) With Various Application Methods of Broflanilide, a Novel Meta-Diamide Insecticide.

Wireworms are primary pests of potatoes in Canada. Presently, the highly toxic organophosphate phorate (i.e., Thimet 20G) is the only effective insecticide in use in Canada. As such, there is an urgent need for novel alternative treatments that provide competitive tuber blemish protection and wireworm reduction with a safer human and environmental portfolio. Herein we evaluated broflanilide, a novel meta-diamide insecticide for both tuber protection and wireworm mortality. When evaluated in field trials in Agassiz, British Columbia over 6 yr, broflanilide applied as a seed piece treatment (SPT) to mother tubers at 1.5-2.0 g AI/100 kg seed (approx. 50 g AI/ha), or as an in-furrow spray (IFS) at 0.23-0.25 g AI/100 m row (approx. 25 g AI/ha) was as effective at reducing blemishes to daughter tubers by wireworms (Agriotes obscurus) as phorate (Thimet 20G at 3230 g AI/ha), bifenthrin (Capture 2EC IFS at 300 g AI/ha) and clothianidin (Titan ST at 312.5 g AI/ha). In addition, broflanilide SPT and IFS applied at the above rates reduced resident wireworms (in the field at the time of planting) by 95.4-99.0% and neonate wireworms (produced from eggs laid during the growing season) by 98.1-100%. Similar results were obtained when broflanilide IFS (nonsystemic) was paired with clothianidin SPT (systemic) for broad-spectrum potato insect pest control. Strategies for the use of broflanilide on wheat (e.g., Teraxxa F4) in rotation with potatoes (Cimegra), both registered in Canada in 2020 are discussed.

Novel colorimetric aptasensor based on MOF-derived materials and its applications for organophosphorus pesticides determination.

For the visual detection of four organophosphorus pesticides (OPs), a colorimetric aptasensor was developed based on aptamer-mediated bimetallic metal-organic frameworks (MOFs) nano-polymers. Fe-Co magnetic nanoparticles (MNPs) and Fe-N-C nanozymes were prepared based on pyrolytic reaction, and were labeled with broad spectrum aptamers and complementary chains of organophosphorus pesticides respectively. The hybridization of aptamers and complementary chains led to the formation of nano-polymers. In the presence of target pesticides, they competed with complementary chains for aptamers on Fe-Co MNPs, resulting in a large number of Fe-N-C nanozymes signal labels being released into the supernatant. Fe-N-C nanozymes showed similar activity to peroxidase and catalyzed the 3,3',5,5'-tetramethylbenzidine-hydrogen peroxide (TMB-H2O2) color system to turn the solution blue-green under mild conditions. The magnetic probes had good selectivity and sensitivity, and were easily separated by magnetic absorption. The sensor functioned well under optimal conditions, demonstrating good stability and specificity for four pesticides: phorate, profenofos, isocarbophos and omethoate, and the detection limits of four pesticides were as low as 0.16 ng/mL, 0.16 ng/mL, 0.03 ng/mL and 1.6 ng/mL respectively, and the recovery rate of OPs residue in vegetable samples was satisfactory. The work described here provided a simple, rapid and sensitive way to construct a biosensor.

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

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

Application of Q-TOF-MS based metabonomics techniques to analyze the plasma metabolic profile changes on rats following death due to acute intoxication of phorate.

Organophosphorus pesticides (OPS) are widely used in the world, and many poisoning cases were caused by them. Phorate intoxication is especially common in China. However, there are currently few methods for discriminating phorate poisoning death from phorate exposure after death and interpretation of false-positive results due to the lack of effective biomarkers. In this study, we investigated the metabonomics of rat plasma at different dose levels of acute phorate intoxication using ultra-performance liquid chromatography quadrupole-time of flight mass spectrometry (UPLC-Q-TOF-MS) analysis. A total of 11 endogenous metabolites were significantly changed in the groups exposed to phorate at LD50 level and three times of LD50 (3LD50) level compared with the control group, which could be potential biomarkers of acute phorate intoxication. Plasma metabonomics analysis showed that diethylthiophosphate (DETP) could be a useful biomarker of acute phorate intoxication. The levels of uric acid, acylcarnitine, succinate, gluconic acid, and phosphatidylcholine (PC) (36:2) were increased, while pyruvate level was decreased in all groups exposed to phorate. The levels of ceramides (Cer) (d 18:0/16:0), palmitic acid, and lysophosphatidylcholine (lysoPC) (18:1) were only changed after 3LD50 dosage. The results of this study indicate that the dose-dependent relationship exists between metabolomic profile change and toxicities associated with apoptosis, fatty acid metabolism disorder, energy metabolism disorder especially tricarboxylic acid (TCA) cycle, as well as liver, kidney, and nervous system functions after acute exposure of phorate. This study shows that metabonomics is a useful tool in identifying biomarkers for the forensic toxicology study of phorate poisoning.

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

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

Evaluating the broad-spectrum efficacy of the acetylcholinesterase oximes reactivators MMB4 DMS, HLö-7 DMS, and 2-PAM Cl against phorate oxon, sarin, and VX in the Hartley guinea pig.

Organophosphorus (OP) compounds, including pesticides and chemical warfare nerve agents (CWNA), are threats to the general population as possible weapons of terrorism or by accidental exposure whether through inadvertent release from manufacturing facilities or during transport. To mitigate the toxicities posed by these threats, a therapeutic regimen that is quick-acting and efficacious against a broad spectrum of OPs is highly desired. The work described herein sought to assess the protective ratio (PR), median effective doses (ED50), and therapeutic index (TI = oxime 24-h LD50/oxime ED50) of MMB4 DMS, HLö-7 DMS, and 2-PAM Cl against the OPs sarin (GB), VX, and phorate-oxon (PHO). All OPs are representative of the broader classes of G and V chemical warfare nerve agents and persistent pesticides. MMB4 DMS and HLö-7 DMS were previously identified as comparative efficacy leads warranting further evaluations. 2-PAM Cl is the U.S. FDA-approved standard-of-care oxime therapy for OP intoxication. Briefly, PRs were determined in male guinea pigs by varying the subcutaneously (SC) delivered OP dose followed then by therapy with fixed levels of the oxime and atropine (0.4 mg/kg; administered intramuscularly [IM]). ED50s were determined using a similar approach except the OP dose was held constant at twice the median lethal dose (2 × LD50) while the oxime treatment levels were varied. The ED50 information was then used to calculate the TI for each OP/oxime combination. Both MMB4 DMS and HLö-7 DMS provided significant protection, i.e., higher PR against GB, VX, and PHO when compared to atropine controls, but significance was not readily demonstrated across the board when compared against 2-PAM Cl. The ED50 values of MMB4 DMS was consistently lower than that of the other oximes against all three OPs. Furthermore, based on those ED50s, the TI trend of the various oximes against both GB and VX was MMB4 DMS > HLö-7 DMS > 2-PAM Cl, while against PHO, MMB4 DMS > 2-PAM Cl > HLö-7 DMS.

Bioremediation of organophosphorus pesticide phorate in soil by microbial consortia.

Microbial consortia isolated from aged phorate contaminated soil were used to degrade phorate. The consortia of three microorganisms (Brevibacterium frigoritolerans, Bacillus aerophilus and Pseudomonas fulva) could degrade phorate, and the highest phorate removal (between 97.65 and 98.31%) was found in soils inoculated with mixed cultures of all the three bacterial species. However, the mixed activity of any of two of these bacteria was lower than mixed consortia of all the three bacterial species. The highest degradation by individual mixed consortia of (B. frigoritolerans+B.aerophilus, B. aerophilus+P. fulva and B. frigoritolerans+P. fulva) appeared in soil between (92.28-94.09%, 95.45-97.15% and 94.08-97.42%, respectively). Therefore, inoculation of highly potential microbial consortia isolated from in situ contaminated soil could result in most effective bioremediation consortia for significantly relieving soils from phorate residues. This much high phorate remediation from phorate contaminated soils have never been reported earlier by mixed culture of native soil bacterial isolates.

Kinetic analysis of oxime-assisted reactivation of human, Guinea pig, and rat acetylcholinesterase inhibited by the organophosphorus pesticide metabolite phorate oxon (PHO).

Phorate is a highly toxic agricultural pesticide currently in use throughout the world. Like many other organophosphorus (OP) pesticides, the primary mechanism of the acute toxicity of phorate is acetylcholinesterase (AChE) inhibition mediated by its bioactivated oxon metabolite. AChE reactivation is a critical aspect in the treatment of acute OP intoxication. Unfortunately, very little is currently known about the capacity of various oximes to rescue phorate oxon (PHO)-inhibited AChE. To help fill this knowledge gap, we evaluated the kinetics of inhibition, reactivation, and aging of PHO using recombinant AChE derived from three species (rat, guinea pig and human) commonly utilized to study the toxicity of OP compounds and five oximes that are currently fielded (or have been deemed extremely promising) as anti-OP therapies by various nations around the globe: 2-PAM Cl, HI-6 DMS, obidoxime Cl2, MMB4-DMS, and HLö7 DMS. The inhibition rate constants (ki) for PHO were calculated for AChE derived from each species and found to be low (i.e., 4.8×103 to 1.4×104M-1min-1) compared to many other OPs. Obidoxime Cl2 was the most effective reactivator tested. The aging rate of PHO-inhibited AChE was very slow (limited aging was observed out to 48h) for all three species. CONCLUSIONS: (1) Obidoxime Cl2 was the most effective reactivator tested. (2) 2-PAM Cl, showed limited effectiveness in reactivating PHO-inhibited AChE, suggesting that it may have limited usefulness in the clinical management of acute PHO intoxication. (3) The therapeutic window for oxime administration following exposure to phorate (or PHO) is not limited by aging.

Prenatal organophosphate insecticide exposure and infant sensory function.

BACKGROUND: Occupational studies suggest that exposure to organophosphate insecticides (OPs) can lead to vision or hearing loss. Yet the effects of early-life exposure on visual and auditory function are unknown. Here we examined associations between prenatal OP exposure and grating visual acuity (VA) and auditory brainstem response (ABR) during infancy. METHODS: 30 OPs were measured in umbilical cord blood using gas chromatography tandem mass spectrometry in a cohort of Chinese infants. Grating visual acuity (VA) (n = 179-200) and auditory brainstem response (ABR) (n = 139-183) were assessed at 6 weeks, 9 months, and 18 months. Outcomes included VA score, ABR wave V latency and central conduction time, and head circumference (HC). Associations between sensory outcomes during infancy and cord OPs were examined using linear mixed models. RESULTS: Prenatal chlorpyrifos exposure was associated with lower 9-month grating VA scores; scores were 0.64 (95% CI: -1.22, -0.06) points lower for exposed versus unexposed infants (p = 0.03). The OPs examined were not associated with infant ABR latencies, but chlorpyrifos and phorate were both significantly inversely associated with HC at 9 months; HCs were 0.41 (95% CI: 0.75, 0.6) cm and 0.44 (95% CI: 0.88, 0.1) cm smaller for chlorpyrifos (p = 0.02) and phorate (p = 0.04), respectively. CONCLUSIONS: We found deficits in grating VA and HC in 9-month-old infants with prenatal exposure to chlorpyrifos. The clinical significance of these small but statistically significant deficits is unclear. However, the disruption of visual or auditory pathway maturation in infancy could potentially negatively affect downstream cognitive development.

[Clinical effect of alanyl glutamine in the treatment of patients with gastrointestinal function obstacle caused by severe phorate poisoning].

Objective: To observe the therapeutic efficacy of alanyl glutamine injection on patients with gastrointestinal function obstacle caused by severe phorate poisoning. Methods: A total of 80 eligible patients with gastrointestinal function obstacle caused by severe phorate poisoning were randomly divided into the control group (n=40) and treatment group (n=40) . The control group was treated with the conventional therapy, which included forbidden diet, atropine, pralidoxime iodide, anti-inflammatory, albumin infusion, ω-3 fish oil fat emulsion, protection of organs function, blood perfusion, and Fat Emulsion, Amino Acids (17) and Glucose Injection. The treatment group was treated with alanyl glutamine injection plus the conventional therapy. To observe the time of recovering to normal of gastrointestinal function between the two groups, compared the AChE activity and changes of prealbumin, albumin and total protein of the two groups respectively. Furthermore, the total atropine dosage, the total pralidoxime iodide dosage and ICU stay time between the two groups were also compared. Results: The gastrointestinal function recovery time of patients in the treatment group was less than the control group, the difference was statistically significant (P<0.05) . From the third day of treatment, the serum cholinesterase activity of the treatment group was higher than the control group, the difference was statistically significant (P<0.05) . On the 5th day and 10th day of the treatment, the prealbumin, albumin and total protein of the treatment group were significantly higher than these indexes of the control group in the same period, the difference were statistically significant (P<0.05) . The total atropine dosage, the total pralidoxime iodide dosage and ICU stay time in the treatment group were lower than the control group, the difference were statistically significant (P<0.05) . Conclusion: Alanyl glutamine injection has a great therapeutic effect for gastrointestinal function obstacle patients caused by severe phorate poisoning.

Phorate induced oxidative stress, DNA damage and differential expression of p53, apaf-1 and cat genes in fish, Channa punctatus (Bloch, 1793).

The present study was conducted to assess the in-vivo activities of certain molecular biomarkers under the impact of phorate exposure. Fish, Channa punctatus (35 ± 3.0 g; 14.5 ± 1.0 cm; Actinopterygii) were subjected to semi-static conditions having 5% (0.0375 mg/L for T1 group) and 10% of 96 h-LC50 (0.075 mg/L for T2 group) of phorate exposure for 15 and 30 d. The oxidative stress was assessed in terms of superoxide dismutase (SOD) and catalase (CAT) activities. DNA damage was measured as induction of micronuclei (MN) and consequent differential expression of apoptotic genes-tumor suppressor (p53), apoptotic peptidase activating factor-1 (apaf-1) and catalase (cat) in liver and kidney, two major sites of biotransformation in fish, were quantified. Our findings reveal significant (p < 0.001) augmentations in SOD and CAT activities of liver and kidney tissues. MN frequency in erythrocytes of fish also increases significantly (p < 0.05) in a dose- and time-dependent manner. The mRNA level of p53 increased significantly (p < 0.05) in liver at 10% of 96 h-LC50 of phorate exposure after 30 d suggesting generation of stress due to accumulation of reactive oxygen species (ROS). Eventually, these findings decipher the dual role of ROS in generating genotoxicity as is evident by micronuclei induction and differential regulation of p53, apaf-1 and cat genes during the phorate induced DNA damage and apoptosis in test fish. The experimental inferences drawn on the basis of activities of aforesaid biomarkers shall be helpful in elucidating the possible causes of apoptosis under stressful conditions. Further, this study finds ample application in biomonitoring of phorate polluted aquatic ecosystem.

Evaluation of absorbent materials for use as ad hoc dry decontaminants during mass casualty incidents as part of the UK's Initial Operational Response (IOR).

The UK's Initial Operational Response (IOR) is a revised process for the medical management of mass casualties potentially contaminated with hazardous materials. A critical element of the IOR is the introduction of immediate, on-scene disrobing and decontamination of casualties to limit the adverse health effects of exposure. Ad hoc cleansing of the skin with dry absorbent materials has previously been identified as a potential means of facilitating emergency decontamination. The purpose of this study was to evaluate the in vitro oil and water absorbency of a range of materials commonly found in the domestic and clinical environments and to determine the effectiveness of a small, but representative selection of such materials in skin decontamination, using an established ex vivo model. Five contaminants were used in the study: methyl salicylate, parathion, diethyl malonate, phorate and potassium cyanide. In vitro measurements of water and oil absorbency did not correlate with ex vivo measurements of skin decontamination. When measured ex vivo, dry decontamination was consistently more effective than a standard wet decontamination method ("rinse-wipe-rinse") for removing liquid contaminants. However, dry decontamination was ineffective against particulate contamination. Collectively, these data confirm that absorbent materials such as wound dressings and tissue paper provide an effective, generic capability for emergency removal of liquid contaminants from the skin surface, but that wet decontamination should be used for non-liquid contaminants.

Phorate can reverse P450 metabolism-based herbicide resistance in Lolium rigidum.

BACKGROUND: Organophosphate insecticides can inhibit specific cytochrome P450 enzymes involved in metabolic herbicide resistance mechanisms, leading to synergistic interactions between the insecticide and the herbicide. In this study we report synergistic versus antagonistic interactions between the organophosphate insecticide phorate and five different herbicides observed in a population of multiple herbicide-resistant Lolium rigidum. RESULTS: Phorate synergised with three different herbicide modes of action, enhancing the activity of the ALS inhibitor chlorsulfuron (60% LD50 reduction), the VLCFAE inhibitor pyroxasulfone (45% LD50 reduction) and the mitosis inhibitor trifluralin (70% LD50 reduction). Conversely, phorate antagonised the two thiocarbamate herbicides prosulfocarb and triallate with a 12-fold LD50 increase. CONCLUSION: We report the selective reversal of P450-mediated metabolic multiple resistance to chlorsulfuron and trifluralin in the grass weed L. rigidum by synergistic interaction with the insecticide phorate, and discuss the putative mechanistic basis. This research should encourage diversity in herbicide use patterns for weed control as part of a long-term integrated management effort to reduce the risk of selection of metabolism-based multiple herbicide resistance in L. rigidum. © 2016 Society of Chemical Industry.

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

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

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

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

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

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

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

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