Liquid chromatography–tandem mass spectrometry method for the simultaneous quantitative determination of the organophosphorus pesticides dimethoate, fenthion, diazinon and chlorpyrifos in human blood

Development and validation of a multi-substance method for routine analysis of pesticides in post-mortem samples by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

Pesticides play an important role in forensic toxicology and are usually classified as a single class of chemicals. Despite their commonly perceived unity, pesticides encompass a spectrum of compounds, including organophosphates, carbamates, pyrethroids or organochlorines, among others, each with varying degrees of toxicity. Pesticide analysis in post-mortem samples can be difficult due to the complexity of the samples and to the high toxicity of these compounds. The aim of this study was to develop and validate an easy to use, sensitive, and robust method, using ultra-performance liquid chromatography-tandem mass spectrometry to be incorporated in the routine flow for pesticide analysis in post-mortem blood samples. Described herein is a streamlined, expeditious, yet highly efficient method facilitating the screening, qualitative assessment, and quantitative confirmation of 15 pesticides, including acetamiprid, azinphos-ethyl, bendiocarb, carbofuran, chlorfenvinphos, dimethoate, imidaclopride, malathion, methiocarb, methomyl, parathion, pirimicarb, strychnine, tetrachlorvinphos, and thiacloprid in post-mortem blood, recognizing the pivotal role blood plays in forensic investigations. The developed method was linear from 10 to 200 ng/mL; limits of detection were between 1 and 10 ng/mL, depending on the compound; it was successfully evaluated a dilution ratio of 1-2, 5 and 10; and 8 substances showed maximum stability for the time interval studied. This UHPLC-MS/MS method is useful and a powerful tool in a toxicology lab because it is fast, simple, effective, and trustworthy. The results of this validation highlight the robustness of the analytical method, providing a valuable tool for the accurate and sensitive detection of pesticides in post-mortem blood. Poised for routine implementation, this method has already found success in suspected intoxication cases, promising to elevate the standards of forensic pesticide analysis.

A Novel Molecularly Imprinted Quartz Crystal Microbalance Sensor Based on Erbium Molybdate Incorporating Sulfur-Doped Graphitic Carbon Nitride for Dimethoate Determination in Apple Juice Samples

Dimethoate (DIM) as an organophosphorus pesticide is widely utilized especially in the cultivation of vegetables and fruits due to its killing effect on harmful insects. However, unconscious use of DIM in large amounts can also cause serious health problems. For these reasons, rapid and reliable detection of DIM from food samples is significant. In this study, a novel quartz crystal microbalance (QCM) sensor based on erbium molybdate incorporating sulfur-doped graphitic carbon nitride (EM/S-g-C3N4) and a molecularly imprinting polymer (MIP) was designed for DIM detection in apple juice samples. Firstly, an EM/S-g-C3N4 nanocomposite with high purity was prepared under hydrothermal conditions at high temperatures over a long period of time. After the modification of the EM/S-g-C3N4 nanocomposite on a QCM chip, the polymerization solution including N,N'-azobisisobutyronitrile (AIBN) as an initiator, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, methacryloylamidoglutamic acid (MAGA) as a monomer, and DIM as an analyte was prepared. Then, the polymerization solution was dropped on an EM/S-g-C3N4 nanocomposite modified QCM chip and an ultraviolet polymerization process was applied for the formation of the DIM-imprinted polymers on the EM/S-g-C3N4 nanocomposite modified QCM chip. After the polymerization treatment, some characterization studies, including electrochemical, microscopic, and spectroscopic methods, were performed to illuminate the surface properties of the nanocomposite and the prepared QCM sensor. The values of the limit of quantification (LOQ) and the detection limit (LOD) of the prepared QCM sensor were as 1.0 × 10-9 M and 3.3 × 10-10 M, respectively. In addition, high selectivity, stability, reproducibility, and repeatability of the developed sensor was observed, providing highly reliable analysis results. Finally, thanks to the prepared sensor, it may be possible to detect pesticides from different food and environmental samples in the future.

An ultra-sensitive photoelectrochemical sensor for chlorpyrifos detection based on a novel BiOI/TiO2 n-n heterojunction

Due to widespread application of chlorpyrifos for controlling pests in agriculture, the continuous accumulation of chlorpyrifos residue has caused serious environmental pollution.The detection of chlorpyrifos is of great significance for humans and environment because it can arise a series of diseases by inhibiting acetylcholinesterase (AChE) activity. Photoelectrochemical sensing, as an emerging sensing technology, has great potential in the detection of chlorpyrifos. It is urgent that find a suitable photoelectric sensing strategy to effectively monitor chlorpyrifos. Herein, an n-n heterojunction was constructed by uniformly immobilizing n-type 3DBiOI, which had loose porous structure composed of numerous small and thin nanosheets, on the surface of TiO₂ with anatase/rutile (AR-TiO₂) heterophase junction. Under light irradiation, the proposed BiOI/AR-TiO₂ n-n heterojunction exhibited excellent optical absorption characteristics and photoelectrochemical activity. Additionally, the photoelectrochemical sensing platform demonstrated excellent analytical performance in monitoring chlorpyrifos. Under optimized conditions, it showed a wide detection range of 1 pg mL^-1- 200 ng mL^-1 and a detection limit (S/N = 3) as low as 0.24 pg mL^-1, with superior selectivity and stability. The ultra-sensitivity and great specificity for detection of chlorpyrifos can be ascribed to chelation between Bi (Ⅲ) and C=N and P=S bonds in chlorpyrifos, which had been confirmed in this work. Meanwhile, the PEC sensor also had potential application value for monitoring chlorpyrifos in water samples, lettuce and pitaya, which the recoveries of samples ranged from 96.9% to 104.7% with a relative standard deviation (RSD) of 1.11%-5.93%. This sensor provided a novel idea for constructing heterojunctions with high photoelectric conversion efficiency and had a high application prospect for the detection of chlorpyrifos and other structural analogues.

Recent advancements in non-enzymatic electrochemical sensor development for the detection of organophosphorus pesticides in food and environment

Organophosphorus Pesticides (OPPs) are among the extensively used pesticides throughout the world to boost agricultural production. However, persistent residues of these toxic pesticides in various vegetables, fruits, and drinking water poses detrimental health effects. Consequently, the rapid monitoring of these harmful chemicals through simple and cost-effective methods has become crucial. In such an instance, electrochemical methods offer simple, rapid, sensitive, reproducible, and affordable detection pathways. To overcome the limitations associated with electrochemical enzymatic sensors, non-enzymatic sensors have emerged as promising and simpler alternatives. The non-enzymatic sensors have demonstrated superior activity, reaching detection limit up to femto (10-15) molar concentration in recent years, leveraging higher selectivity obtained through the molecularly imprinted polymers, synergistic effects between carbonaceous nanomaterials and metals, metal oxide alloys, and other alternative approaches. Herein, this review paper provides an overview of the recent advancements in the development of non-enzymatic electrochemical sensors for the detection of commonly used OPPs, such as Chlorpyrifos (CHL), Diazinon (DZN), Malathion (MTN), Methyl parathion (MP) and Fenthion (FEN). The design method of the electrodes, electrode functioning mechanism, and their analytical performance metrics, such as limit of detection, sensitivity, selectivity, and linearity range, were reviewed and compared. Furthermore, the existing challenges within this rapidly growing field were discussed along with their potential solutions which will facilitate the fabrication of advanced and sustainable non-enzymatic sensors in the future.

Interactions of organophosphorus pesticides with ATP-Binding Cassette (ABC) drug transporters

Although pharmaceutical companies have to study drug transporter interaction, environmental contaminant interactions with these transporters are not well characterized. In this study, we demonstrated using in vitro transfected cell line that some organophosphorus pesticides are able to interact with drug efflux transporters like P-glycoprotein, BCRP and MRPs.According to our results, dibrom was found to inhibit only Hoechst binding site of P-gp with an IC50 closed to 77 µM, phosmet inhibited BCRP efflux with an IC50 of 42 µM and only profenofos was able to inhibit BCRP, MRPs and two P-gp binding sites. As profenofos appeared to be a potent ABC transporter inhibitor, we studied its potential substrate property towards P-gp.Using a docking approach, we developed an in silico tool to study pesticide properties to be a probe or inhibitor of P-gp transporter. From both in silico and in vitro results, profenofos was not considered as a P-gp substrate.Combining both in vitro and docking methods appears to be an attractive approach to select pesticides that would not pass into the blood systemic circulation.

A comprehensive review on electrochemical and optical aptasensors for organophosphorus pesticides

There has been a rise in pesticide use as a result of the growing industrialization of agriculture. Organophosphorus pesticides have been widely applied as agricultural and domestic pest control agents for nearly five decades, and they remain as health and environmental hazards in water supplies, vegetables, fruits, and processed foods causing serious foodborne illness. Thus, the rapid and reliable detection of these harmful organophosphorus toxins with excellent sensitivity and selectivity is of utmost importance. Aptasensors are biosensors based on aptamers, which exhibit exceptional recognition capability for a variety of targets. Aptasensors offer numerous advantages over conventional approaches, including increased sensitivity, selectivity, design flexibility, and cost-effectiveness. As a result, interest in developing aptasensors continues to expand. This paper discusses the historical and modern advancements of aptasensors through the use of nanotechnology to enhance the signal, resulting in high sensitivity and detection accuracy. More importantly, this review summarizes the principles and strategies underlying different organophosphorus aptasensors, including electrochemical, electrochemiluminescent, fluorescent, and colorimetric ones.

Recent advances in electrochemical and optical sensing of the organophosphate chlorpyrifos: a review

Chlorpyrifos (CP) is one of the most popular organophosphorus pesticides that is commonly used in agricultural and nonagricultural environments to combat pests. However, several concerns regarding contamination due to the unmitigated use of chlorpyrifos have come up over recent years. This has popularized research on various techniques for chlorpyrifos detection. Since conventional methods do not enable smooth detection, the recent trends of chlorpyrifos detection have shifted toward electrochemical and optical sensing techniques that offer higher sensitivity and selectivity. The objective of this review is to provide a brief overview of some of the important and innovative contributions in the field of electrochemical and optical sensing of chlorpyrifos with a primary focus on the comparative advantages and shortcomings of these techniques. This review paper will help to offer better perspectives for research in organophosphorus pesticide detection in the future.

Rapid and non-invasive surface-enhanced Raman spectroscopy (SERS) detection of chlorpyrifos in fruits using disposable paper-based substrates charged with gold nanoparticle/halloysite nanotube composites

Chlorpyrifos is one of the most widely used organophosphate insecticides in agricultural production. Nevertheless, the residues of chlorpyrifos in agricultural by-product seriously threaten human health. Thus, the ultrasensitive detection of chlorpyrifos residues in agri-food products is of great demand. Herein, an AuNP/HNT-assembled disposable paper SERS substrate was prepared by an electrostatic self-assembly method to detect chlorpyrifos residues. The AuNP/HNT paper substrate exhibited high SERS activity, good reproducibility, and long-term stability, which was successfully used for quantitative detection of chlorpyrifos; the detection limit reached 7.9 × 10^-9 M. For spiked apple samples the calculated recovery was 87.9% with a RSD value of 6.1%. The excellent detection ability of AuNP/HNT paper-based SERS substrate indicated that it will play an important role in pesticide detection in the future. AuNP/HNT assembled disposable paper SERS substrate was prepared by an electrostatic self-assembly method to detect chlorpyrifos residues in fruits.

Modular graphene mediator film-based electrochemical pocket device for chlorpyrifos determination

In this work, a redox-graphene (Rx-Gr) film with electron-mediating ability has been integrated into a modular flexible pocket device, giving rise to a reusable biosensing platform. The Rx-Gr has been obtained in water from graphite taking advantage of catechin, a redox-antioxidant, able to assist the sonochemical layered-material exfoliation, conferring electron mediating feature. A film composed exclusively of Rx-Gr has been transferred via thermal rolling onto a flexible PET-support that was used as the biosensor base. The biosensing platform, composed of office-grade materials, was then fabricated using a cutter-plotter and assembled by thermal lamination; an interchangeable paper-based strip was used to host the enzymatic reaction and drive the capillary flow. An acetylcholinesterase-based inhibition assay has been optimized onboard the pocket device to determine chlorpyriphos, a widespread environmental pesticide. The proposed set-up allows the determination of chlorpyriphos at low overpotential (0.2 V) with satisfactory sensitivity (LOD = 0.2 ppb), thanks to the straightforward electroactivity of the Rx-Gr film towards thiocholine (enzymatic product). The modular design allows 5 consecutive complete inhibition assays (control + inhibition measure) retaining the performance (RSD = 5.4%; n = 5). The coupling of bench-top technologies and a new functional graphene film resulted in the development of a cost-effective, reusable, transportable, and within everyone's reach biosensing platform.

Preparation of magnetic molecularly imprinted polymer based on multiwalled carbon nanotubes for selective dispersive micro-solid phase extraction of fenitrothion followed by ion mobility spectrometry analysis

A novel molecularly imprinted polymer based on magnetic multi-walled carbon nanotubes was fabricated and applied for selective dispersive micro-solid phase extraction of fenitrothion prior its determination by ion mobility spectrometry. The composite was synthesized using magnetic multi-walled carbon nanotubes as the support. Methacrylic acid was used as the functional monomer, fenitrothion as the template, ethylene glycol dimethacrylate as the cross-linker and 2,2-azoisobutyronitrile as the initiator. The resultant polymer was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, Brunauer-Emmet-Teller analysis, thermogravimetric analysis and vibrating sample magnetometer techniques. Experimental factors affecting the extraction efficiency such as pH and amount of sorbent were evaluated. Under optimum experimental conditions, the developed method displayed the linear range of 5-220 μg L^-1 with a detection limit (LOD) of 1.3 μg L^-1 . The intra and inter-day relative standard deviations (RSD%) for determination of fenitrothion were 3.6 and 4.7% (n = 6), respectively. Ultimately, the proposed method was used to monitoring of trace amounts of fenitrothion in fruit,vegetable and water samples. This article is protected by copyright. All rights reserved.

Liquid chromatography tandem mass spectrometry for the determination of nine insecticides and fungicides in human postmortem blood and urine

Pesticide poisoning is a common occurrence due to their widespread use, easy access and high toxicity even in small concentrations. The most common poisoning fatalities have been observed due to exposure to organophosphates, carbamates and neonicotinoids, thus development of a method for the rapid determination of these compounds in blood and urine is of great importance for clinical and toxicology laboratories. A simple, fast and reliable method was developed for the determination of 9 pesticides in blood and urine using HPLC-MS/MS instrumentation. In order to find the most suitable sample pretreatment technique, three different sample preparation procedures: SPE, protein precipitation and QuEChERS were compared. The final optimized analytical method was fully validated with the values of parameters such as calibration linearity, accuracy, precision, recovery, matrix effect and stability being acceptable. The method proved reliable, accurate, robust and sensitive and was successfully applied for the quantitation of pesticides in three postmortem cases of pesticides poisoning.

A hollow visible-light-responsive surface molecularly imprinted polymer for the detection of chlorpyrifos in vegetables and fruits

A visible-light-responsive azobenzene derivative, 3,5-dichloro-4-((2,6-dichloro-4-(methacryloyloxy)phenyl)diazenyl)benzoic acid, was synthesized and used as the functional monomer to fabricate a visible-light-responsive core-shell structured surface molecularly imprinted polymer (PS-co-PMAA@VSMIP). After removal of the sacrificial PS-co-PMAA core, a hollow structured surface molecularly imprinted polymer (HVSMIP) was obtained. Both the PS-co-PMAA@VSMIP and HVSMIP were used for the detection of chlorpyrifos, a moderately toxic organophosphate pesticide. They exhibited good visible-light-responsive properties (550 nm for trans→cis and 440 nm for cis→trans isomerization for an azobenzene chromophore) in ethanol/water (9:1, v/v). Compared with the PS-co-PMAA@VSMIP, the HVSMIP had a larger surface area, pore volume, binding capacity, imprinting effect, maximum chemical binding capacity, dissociation constant, and photo-isomerization rate. The HVSMIP was applied to detect trace chlorpyrifos in fruit and vegetable samples. This was achieved by measuring the trans→cis rate constant of the HVSMIP in the sample solution, with good recoveries, low relative standard deviations, and a low detection limit.

Ultrasensitive fluorescent detection of pesticides in real sample by using green carbon dots

Pesticides, widely used in modern agriculture, could potentially cause environmental pollution and affect human lives. Hence, the development of a highly sensitive sensing element to detect pesticide residues is crucial for food safety and ecosystem protection. Optical methods based on fluorescence properties provide an ideal approach for screening and quantification of these compounds in different medias including water, plant, and nutritional products. The development of fluorescence emitting carbon dot-based sensors for monitoring pesticides has attracted great attention in recent years. In comparison to other fluorophores, carbon dots have more promising optical features, higher quantum yields and better biocompatibility. This article aims to present a novel fluorescent sensing method of diazinon, glyphosate, and amicarbazone using plant-based carbon dots. A comprehensive characterization of carbon dots obtained from cauliflower was performed by methods including UV-visible, FTIR spectroscopy, fluorometry, AFM, DLS, and zeta sizer. Following this step, carbon dots were used to detect pesticides. The fluorescence quenching property of carbon dots has been utilized to identify detection limit of 0.25, 0.5, and 2 ng ml-1 for diazinon, amicarbazone, and glyphosate, respectively. Also, real sample study revealed that the detection of pesticides accompanied by our developed nano-sensor is repeatable and accurate. According to carbon dots specificity determination, the prepared nano sensor does not have the potential to identify "bromacil" and "dialen super" pesticides but the other three mentioned pesticides are detectable. The results confirm that synthesized green carbon dots are well qualified for application in food safety and environmental monitoring.

Efficacy of an organophosphorus hydrolase enzyme (OpdA) in human serum and minipig models of organophosphorus insecticide poisoning

Objectives: Current therapeutic options for organophosphorus (OP) insecticide self-poisoning including atropine and oximes are inadequate and case fatality may exceed 20%. An OP hydrolase enzyme, OpdA, has been used for environmental cleansing of OP insecticides and prevented death in rat and non-human primate models of OP insecticide poisoning if given very quickly after exposure. We here tested OpdA's ability to break down OP insecticides in human serum and in clinically relevant minipig models of OP insecticide poisoning.Methods: Human serum was spiked with seven diverse WHO Class II OP insecticides (chlorpyrifos, quinalphos, diazinon, dimethoate, fenthion, phenthoate, and profenofos) and the effect of OpdA on degradation measured. The pharmacodynamic and clinical effects of OpdA treatment were studied in Gottingen minipigs orally poisoned with agricultural formulations of dimethoate EC40 or methyl parathion EC60; pharmacodynamic effects were also assessed in profenofos EC50-poisoned pigs.Results: OpdA effectively hydrolysed OP insecticides in human serum, with rates varying from 856 (SD 44) down to 0.107 (SD 0.01) moles of substrate hydrolysed/mole of enzyme/sec (k_cat) for quinalphos and phenthoate, respectively, although at rates 2-3 log orders less than found in vitro in buffered solution. It showed clinical benefit in minipig models, reducing the dose of noradrenaline required to sustain an adequate mean arterial pressure after dimethoate (mean 0.149 [SD 0.10] μg/kg/h vs. 1.07 [SD 0.77] μg/kg/h, p < .0001) and methyl parathion (mean 0.077 [SD 0.08] μg/kg/h vs. 0.707 [SD 0.49] μg/kg/h, p < .0001) poisoning. OpdA reduced blood OP insecticide concentration and acetylcholinesterase inhibition after poisoning by dimethoate, methyl parathion, and profenofos insecticides.Conclusions: In vitro incubation of OpdA in human serum showed hydrolysis of diverse OP insecticides, although at lower rates than found in buffer solutions. This activity results in clinical and pharmacodynamic efficacy in vivo against several OP insecticides. These results support the testing of OpdA in further animal models before considering human trials to determine whether it may become an urgently required novel therapeutic agent for OP insecticide self-poisoning.

Novel magnetic hollow zein nanoparticles for preconcentration of chlorpyrifos from water and soil samples prior to analysis via high-performance liquid chromatography (HPLC)

Herein, magnetically hollow zein nanoparticles were synthesized and used as a magnetic sorbent for the preconcentration of chlorpyrifos and its analysis by high-performance liquid chromatography (HPLC). Morphology of the sorbent was characterized by transmission electron microscopy (TEM). In this study, the effects of important parameters such as pH of the solution, adsorption and desorption time, type and volume of desorption solvent, and salt addition were investigated. Under optimized experimental conditions, the linear range was from 50 to 2000 μg mL-1, and an LOD of 25 μg L-1 was calculated. The relative standard deviations (RSD) varied from 3.8 to 5.1% (n = 5). The enrichment factors for 50 and 100 μg L-1 samples were calculated as 187 and 210, respectively. The developed method was successfully applied in soil and water samples and showed good extraction recoveries.

Interactions of organophosphorus pesticides with solute carrier (SLC) drug transporters

1. Organophosphorus pesticides (OPs) are known to interact with human ATP-binding cassette drug efflux pumps. The present study was designed to determine whether they can also target activities of human solute carrier (SLC) drug transporters. 2. The interactions of 13 OPs with SLC transporters involved in drug disposition, such as organic cation transporters (OCTs), multidrug and toxin extrusion proteins (MATEs), organic anion transporters (OATs) and organic anion transporting polypeptides (OATPs), were mainly investigated using transporter-overexpressing cell clones and fluorescent or radiolabeled reference substrates. 3. With a cut-off value of at least 50% modulation of transporter activity by 100 µM OPs, OAT1 and MATE2-K were not impacted, whereas OATP1B1 and MATE1 were inhibited by two and three OPs, respectively. OAT3 activity was similarly blocked by three OPs, and was additionally stimulated by one OP. Five OPs cis-stimulated OATP2B1 activity. Both OCT1 and OCT2 were inhibited by the same eight OPs, including fenamiphos and phosmet, with IC₅₀ values however in the 3-30 µM range, likely not relevant to environmental exposure. 4. These data demonstrated that various OPs inhibit SLC drug transporter activities, especially those of OCT1 and OCT2, but only when used at high concentrations not expected to occur in environmentally-exposed humans.

Molecularly imprinted polymer nanoparticles-based electrochemical sensor for determination of diazinon pesticide in well water and apple fruit samples

In this research, an electrochemical sensor based on molecularly imprinted polymer (MIP) nanoparticles for selective and sensitive determination of diazinon (DZN) pesticides was developed. The nanoparticles of diazinon imprinted polymer were synthesized by suspension polymerization and then used for modification of carbon paste electrode (CPE) composition in order to prepare the sensor. Cyclic voltammetry (CV) and square wave voltammetry (SWV) methods were applied for electrochemical measurements. The obtained results showed that the carbon paste electrode modified by MIP nanoparticles (nano-MIP-CP) has much higher adsorption ability for diazinon than the CPE based non-imprinted polymer nanoparticles (nano-NIP-CP). Under optimized extraction and analysis conditions, the proposed sensor exhibited excellent sensitivity (95.08 μA L μmol(-1)) for diazinon with two linear ranges of 2.5 × 10(-9) to 1.0 × 10(-7) mol L(-1) (R (2) = 0.9971) and 1.0 × 10(-7) to 2.0 × 10(-6) mol L(-1) (R (2) = 0.9832) and also a detection limit of 7.9 × 10(-10) mol.L(-1). The sensor was successfully applied for determination of diaznon in well water and apple fruit samples with recovery values in the range of 92.53-100.86 %. Graphical abstract Procedure for preparation of electrochemical sensor based on MIP nanoparticles for determination of diazinon.

Organophosphate pesticide method development and presence of chlorpyrifos in the feet of nearctic-neotropical migratory songbirds from Canada that over-winter in Central America agricultural areas

Recent modeling analysis suggests that numerous birds may be at risk of acute poisoning in insecticide-treated fields. Although the majority of avian field studies on pesticides have focused on treated seed, granule, insect or vegetation (oral exposure) ingestion, dermal exposure is an important exposure route when birds come into contact with deposited pesticides on foliage and other surfaces. Some nearctic-neotropical migratory songbirds are likely exposed to pesticides on their non-breeding habitats and include treated crops, plantations or farmlands. In the present study, we developed a method for four environmentally-relevant organophosphate (OP) pesticides (fenthion, fenamiphos, chlorpyrifos and diazinon) in the feet of migratory songbirds (i.e. Common yellowthroat, Gray catbird, Indigo bunting, America redstart, Northern waterthrush, Northern parula, and an additional 12 species of warblers). A total of 190 specimens of the 18 species of songbirds were sampled from available window-killed birds (spring of 2007 and 2011) in downtown Toronto, Canada. The species that were available most likely over-wintered in Mexican/Central American crops such as citrus, coffee and cacao. The feet of the dead birds were sampled and where OP foot exposure likely occurred during over-wintering foraging on pesticide-treated crops. Chlorpyrifos was the only measurable OP (pg mg feet weight(-1)) and in the 2011-collected feet of Black throated blue warbler (0.5), Tennessee warbler (1.0), Northern parula (1.2), Northern waterthrush (0.6), Common yellowthroat (1.0) and the Blue winged warbler (0.9). Dermal contact with OP pesticides during over-wintering in agricultural areas resulted in low levels of chlorpyrifos and long time retention on the feet of a subset of songbirds.

Exonuclease I-aided homogeneous electrochemical strategy for organophosphorus pesticide detection based on enzyme inhibition integrated with a DNA conformational switch

A homogeneous electrochemical strategy for the detection of organophosphorus pesticides based on the inhibition of acetylcholinesterase activity and configuration change of hairpin DNA probes was developed.

Effect of Dimethoate on the Activity of Hepatic CYP450 Based on Pharmacokinetics of Probe Drugs

BACKGROUND

Dimethoate (DM), one of the most widely used systemic organophosphate insecticide, has been reported to exert toxic effects after long-time subchronic exposure. This study aims at investigating the toxic effect of DM on liver after repeated administration of low doses of DM in rats.

METHODS

Twenty Sprague-Dawley rats were randomly divided into the control group (n = 10) and the DM group (n = 10). After 2 weeks' exposure to DM at low dosage (5 mg/kg), biochemical parameters of hepatic functions were measured, histology and CYP450 expressed in liver was detected. The activities of CYP1A2, CYP2C11, CYP2D1, and CYP3A2 were evaluated by the Cocktail method.

RESULTS

The level of AChE (acetylcholinesterase) was significantly decreased, hepatic functions were damaged and the mRNA level of CYP2D1 was significantly increased in the DM group (p < 0.05). The pharmacokinetics of probe drug revealed AUC(0-t), AUC(0-∞), t1/2 and Cmax of metoprolol was shorten in the DM group (p < 0.05). However, there were no statistical differences in MRT, t1/2, CL and Tmax for phenacetin, tolbutamide and midazolam.

CONCLUSIONS

A low dosage of DM could induce the activity of CYP2D1 in liver and increase the metabolism of metoprolol when exposed for 2 weeks.

Surface plasmon resonance sensor based on magnetic molecularly imprinted polymers amplification for pesticide recognition

We reported here a method to enhance detection sensitivity in surface plasmon resonance (SPR) spectroscopy integrated with a surface molecular imprinting recognition system and employing magnetic molecular imprinting polymer nanoparticles for amplifying SPR response. The proposed magnetic molecular imprinting polymer was designed by self-polymerization of dopamine on the Fe3O4 NPs surface in weak base aqueous solution in the presence of template chlorpyrifos (CPF). The imprinted Fe3O4@polydopamine nanoparticles (Fe3O4@PDA NPs) were characterized by Fourier transform infrared spectroscopy, UV-vis absorption spectroscopy, and transmission electron microscopy. The biosensor showed a good linear relationship between the SPR angle shift and the chlorpyrifos concentration over a range from 0.001 to 10 μM with a detection limit of 0.76 nM. A significant increase in sensitivity was therefore afforded through the use of imprinted Fe3O4@PDA NPs as an amplifier, and meanwhile, the imprinted Fe3O4@PDA NPs had an excellent recognition capacity to chlorpyrifos over other pesticides. The excellent sensitivity and selectivity and high stability of the designed biosensor make this magnetic imprinted Fe3O4@PDA NP an attractive recognition element for various SPR sensors for detecting pesticide residuals and other environmentally deleterious chemicals.

Determination of organophosphorus pesticides using dispersive liquid-liquid microextraction combined with reversed electrode polarity stacking mode-micellar electrokinetic chromatography

A rapid and sensitive method using two preconcentration techniques, dispersive liquid-liquid microextraction (DLLME) followed by reversed electrode polarity stacking mode (REPSM) was developed for the analysis of five organophosphorus pesticides (OPPs) by micellar electrokinetic chromatography (MEKC). Parameters that affect the efficiency of the extraction in DLLME and preconcentration by REPSM, such as the kind and volume of the extraction and disperser solvents, salt addition, sample matrix and injection time were investigated and optimized. Under the optimum conditions, the enrichment factors were obtained in the range from 477 to 635. The linearity of the method for parathion, azinphos and fenitrithion was in the range of 20-1000 ng mL(-1), and for malathion and diazinon in the range of 50-1000 ng mL(-1), with correlation coefficients (r(2)) ranging from 0.9931 to 0.9992. The limits of detecton (LODs) at a signal-to-noice ratio of 3 ranged from 3 to 15 ng mL(-1). The relative recoveries of five OPPs from water samples at spiking levels of 20 and 200 ng mL(-1) for parathion, azinphos and fenitrithion, and 50 and 500 ng mL(-1) for malathion and diazinon, were 69.5-103%. The proposed method provided high enrichment factors, good precision and accuracy with a short analysis time.

Determination of 49 organophosphorus pesticide residues and their metabolites in fish, egg, and milk by dual gas chromatography-dual pulse flame photometric detection with gel permeation chromatography cleanup

A new method for the quantitative determination of 49 kinds of organophosphorus pesticide residues and their metabolites in fish, egg, and milk by dual gas chromatography-dual pulse flame photometric detection was developed. Homogenized samples were extracted with acetone and methylene chloride (1 + 1, v/v), and then the extracts were cleaned up by gel permeation chromatography (GPC). The response of each organophosphorus pesticide showed a good linearity with its concentration; the linearity correlation was not less than 0.99. The detection limits (S/N = 3) of pesticides were in the range of 0.001-0.025 mg kg⁻¹. The recovery experiments were performed by blank sample spiked at low, medium, and high fortification levels. The recoveries for fish, egg, and milk were 50.9-142.2, 53.3-137.2, and 50.3-139.4% with relative standard deviations (RSD, n = 6) of 2.3-24.9, 4.3-26.7, and 2.8-32.2%, respectively. The method was applied to detect organophosphorus pesticides in samples collected from the market, and satisfactory results were obtained. This quantitative method was highly sensitive and exact and could be applied to the accurate determination of organophosphorus contaminants in fish, egg, and milk.