Determination Of Dimethoate Research Articles

A new portable electrochemical detection sensor based on molecularly imprinted polymer-modified MOF-808/AB for the highly sensitive and selective determination of dimethoate

Detection of dimethoate (DIM) in fruits and vegetables is crucial for life health and environmental development, but there is still a lack of versatile portable organophosphorus pesticides detection instruments. In this study, a unique portable electrochemical detection system was designed for real-time detection in the field. Meanwhile, a new combination of metal–organic skeleton MOF-808 and acetylene black (AB) was reported for the first time, and an electrochemical sensor for the detection of dimethoate (DIM) was constructed by using a molecularly imprinted polymer (MIP) coated MOF-808/AB. The AB was homogeneously grown on the surface of MOF-808, which ensured the high conductivity and mechanical stability of the material. The experimental results showed that MIP/MOF-808/AB/GCE had a better detection effect on DIM. Under the optimal conditions, the linear range of DIM was 1 × 10-5 – 1 × 10-10 M with a detection limit of 43.05 pM (n = 10) using differential pulse voltammetry.

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.

A deep learning-enabled smartphone platform for rapid and sensitive colorimetric detection of dimethoate pesticide.

A novel deep learning-enabled smartphone platform is developed to assist a colorimetric aptamer biosensor for fast and highly sensitive detection of dimethoate. The colorimetric determination of dimethoate is based on the specific binding of dimethoate and aptamer, which leads to the aggregation of AuNPs in high-concentration NaCl solution, resulting in an obvious color change from red to blue. This color change provides sufficient data for self-learning enabled by a convolutional neural network (CNN) model, which is established to predict dimethoate concentration based on images acquired from a smartphone. To enhance user-friendliness for non-experts, the CNN model is then embedded into a smartphone app, enabling offline detection of dimethoate pesticide in real environments within just 15min using a pre-configured colorimetric probe. The developed platform exhibits superior performance, achieving a regression coefficient of 0.9992 in the concentration range of 0-10μM. Moreover, the app's performance is found to be consistent with the ELISA kit. These remarkable findings demonstrate the potential of combining colorimetric biosensors with smartphone-based deep learning methods for the development of portable and affordable tools for pesticide detection.

Ultrasound-assisted dispersive liquid–liquid microextraction combined with ion mobility spectrometry for the simultaneous preconcentration and determination of dimethoate and chlorpyrifos in fruit, vegetable, and water samples

A rapid, sensitive, and reliable method based on ultrasound- assisted dispersive liquid–liquid microextraction followed by ion mobility spectrometry analysis (UA-DLLME-IMS) is reported for the preconcentration and determination of chlorpyrifos and dimethoate in food and water. The sample pH, volume of dichloromethane (extraction solvent), sonication, and centrifuge time, salt effect and sample volume were individually optimized. Under the optimum conditions, the calibration curves were linear from 5 to 200 µg L−1 and 3 to 280 µg L−1. Limits of detection (LOD) of 1.3 and 0.8 µg L−1 were obtained for chlorpyrifos and dimethoate, respectively. The relative standard deviations at 20 μg L−1 (n = 5) for intra- and inter-day precision were 2.8% and 3.9% for chlorpyrifos and 4.1% and 4.6% for dimethoate, respectively. The procedure was validated for the determination of chlorpyrifos and dimethoate in food and water samples.

Simultaneous determination of dimethoate and its metabolite omethoate in curry leaf using LC-MS/MS and risk assessment.

This study presents the method development, validation, and simultaneous determination of dimethoate and its metabolite omethoate in curry leaf. Samples were extracted following modified quick, easy, cheap, effective, rugged, and safe extraction protocol and analyzed using liquid chromatography-tandem mass spectrometry. The limit of quantification in the matrix was 0.005μgg-1 for dimethoate and omethoate. Extraction using acetonitrile recorded the average recoveries in the range of 82.25 to 112.97% for dimethoate and 85.57 to 107.22% for omethoate at 0.005, 0.025 and 0.050μgg-1 fortification levels and relative standard deviation less than 5%. Similarly, the relative standard deviation values for intraday (Repeatability) and interday (Reproducibility) tests were less than 15%. Dissipation kinetics of dimethoate 30% emulsifiable concentrate at 200 and 400ga.ih-1 recorded initial deposits of 5.20 and 10.05μgg-1 and 0.33 and 0.48μgg-1 for dimethoate and omethoate, respectively, and half-life of 3.07 and 3.34days. The estimated hazard index value found more than one at a day after dimethoate application. It is not safe for consumer health to use curry leaves in the initial days after application.

A ratiometric electrochemical biosensor via alkaline phosphatase mediated dissolution of nano-MnO2 and Ru(III) redox recycling for the determination of dimethoate

A sensitive and ratiometric electrochemical biosensor was developed for the determination of dimethoate via alkaline phosphatase (ALP) mediated dissolution of nano-MnO2 and [Ru(NH3)6]3+(Ru(III)) redox recycling. The electroactive probe Ru(III) was adsorbed on the nano-MnO2 with the high specific surface area through electrostatic interaction to form the MnO2-Ru(III) nanocomposite, which was then fixed on the surface of the glassy carbon electrode. When the dimethoate inhibited the catalytic activity of ALP in a homogeneous system, the hydrolysate L-ascorbic acid (AA) produced by ALP hydrolysis of L-ascorbic acid-trisodium 2-phosphate (AAP) decreased. The solution was then incubated with a glassy carbon electrode modified by MnO2-Ru(III). At this time, only a small amount of MnO2-Ru(III) was decomposed and Ru(III) was rapidly electroreduced to Ru(II) on the surface of the electrode. The in-situ produced Ru(II) was chemically oxidized back to Ru(III) by Fe(III). The redox recycling of Ru(III) was completed and the Ru(III) reduction current signal was amplified. The process consumed part of Fe(III) to reduce the reduction current signal of Fe(III), and the ratio of the two reduction currents (IRu(III)/IFe(III)) increased significantly. The IRu(III)/IFe(III) value increased with the increase of dimethoate concentration in the linear range of 0.01–300 ng mL−1, and the detection limit was 6.3 pg mL−1. It has been successfully applied to the determination of dimethoate in oilseed rape and lettuce with a satisfactory result.

Surface imprinted CoZn-bimetalic MOFs as selective colorimetric probe: Application for detection of dimethoate

Designing simple and selective sensors for on-site recognition of organophosphate toxins (OPs) is of great importance. Here, molecularly imprinted polymer (MIP)-capped CoZn bimetal imidazolate framework (CoZn ZIF) has been introduced as a specific probe for the quantification of dimethoate. The detection is based on its diminishing effect on the catalytic action of ZIF in 3,3′,5,5′-Tetramethylbenzidine (TMB)-hydrogen peroxide (H2O2) reaction. CoZn ZIF catalyzes the dissociation of H2O2 to hydroxyl radicals, which can then oxidize TMB and create a blue colored product. It was demonstrated that the catalytic performance of bimetal metal organic framework (MOF) is higher than that of single metal MOF of Co (ZIF-67) or Zn (ZIF-8). On the other hand, adsorbing dimethoate in the specific MIP sites on the surface of CoZn ZIF declines its catalytic action. This effect was exploited to design a selective colorimetric assay for dimethoate determination in fruit and wastewater samples. The decrease in the absorption intensity of final solution was proportional to the dimethoate concentration in the range of 0.02–1.2 μM, with a detection limit of 5.6 nM. The high specificity of MIP technique and great catalytic activity of CoZn ZIF, as well as the simplicity of colorimetric method led to a reliable screening assay.

A simple spectroscopic method to determine dimethoate in water samples by complex formation

A simple and rapid method for the determination of dimethoate in water was developed based on the monitoring of the complex formation between bis 5-phenyldipyrrinate of nickel (II) and the herbicide dimethoate. The method showed a short response time (10 s), high selectivity (very low interference from other sulfate and salts), high sensitivity (limit of detection (LOD) 0.45 µM, limit of quantitation (LOQ) of 1.39 µM), and a Kd of 2.4 µM. Stoichiometry experiments showed that complex formation occurred with a 1:1 relation. The method was applied to different environmental water samples such as lagoon, stream, urban, and groundwater samples. The results indicated that independently from the water source, the method exhibited high precision (0.25–2.47% variation coefficient) and accuracy (84.42–115.68% recovery). In addition, the method was also tested using an effluent from a wastewater treatment plant from Mexico; however, the results indicated that the presence of organic matter had a pronounced effect on the detection.

Fluorometric microplate-based dimethoate assay using CdSe/ZnS quantum dots coated with a molecularly imprinted polymer.

A microplate-based assay is described for the sensitive and selective fluorometric determination of the pesticide dimethoate. Molecularly imprinted polymer (MIP)-coated CdSe/ZnS quantum dots (QDs) are used as the molecular recognition probe. The MIP-coated QDs were synthesized using one-step reversed-phase microemulsion in the presence of hydrophobic CdSe/ZnS QDs. Copolymerization was performed by using 3-aminopropyltriethoxysilane as the functional monomer, tetraethoxysilane as the cross-linker, and dimethoate as thetemplate. The fluorescence of the coated QDs is quenched by dimethoate when dimethoate becomes rebound on the imprinting sites of the MIP. Under the optimal conditions, fluorescence (best measured at excitation/emisison wavelengths of 380/620nm) drops linearly in the 5.0-150μgL-1dimethoate concentration range, and the limit of detection is 2.1μgL-1 (atS/N= 3). The assay was utilized for dimethoate determination in spiked real samples. Satisfactory recoveries (89.8%-98.0%) with relatively standard deviations of <4.9% are obtained. The method is rapid, cost-effective, sensitive, and selective. The use of microplate allows for the quantitation of a large number of samples simultaneously. Graphical abstract Schematic representation of sensitive and selective fluorometric microplate-based assay for the high-throughput determination of dimethoate (DM) based on recognition of molecularly imprinted polymer (MIP)-coated CdSe/ZnS quantum dots (QDs). DM exerts aquenching effect on the fluorescence of theQDs.

Surface Enhanced Raman Spectroscopy for In-Field Detection of Pesticides: A Test on Dimethoate Residues in Water and on Olive Leaves.

Dimethoate (DMT) is an organophosphate insecticide commonly used to protect fruit trees and in particular olive trees. Since it is highly water-soluble, its use on olive trees is considered quite safe, because it flows away in the residual water during the oil extraction process. However, its use is strictly regulated, specially on organic cultures. The organic production chain certification is not trivial, since DMT rapidly degrades to omethoate (OMT) and both disappear in about two months. Therefore, simple, sensitive, cost-effective and accurate methods for the determination of dimethoate, possibly suitable for in-field application, can be of great interest. In this work, a quick screening method, possibly useful for organic cultures certification will be presented. DMT and OMT in water and on olive leaves have been detected by surface enhanced Raman spectroscopy (SERS) using portable instrumentations. On leaves, the SERS signals were measured with a reasonably good S/N ratio, allowing us to detect DMT at a concentration up to two orders of magnitude lower than the one usually recommended for in-field treatments. Moreover, detailed information on the DMT distribution on the leaves has been obtained by Raman line- (or area-) scanning experiments.

An enhanced oxime-based biomimetic electrochemical sensor modified with multifunctional AuNPs–Co3O4–NG composites for dimethoate determination

An enhanced oxime-based electrochemical sensor decorated with gold nanoparticles (AuNPs) and Co3O4 hexagonal nanosheets coupled with nitrogen-doped graphene has been developed for dimethoate determination dramatically. The introduction of Co3O4 hexagonal nanosheets tackles agglomeration of AuNPs and also enhances the sensitivity of electrochemical sensors greatly. The structure and properties of the synthesized composites were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy, confirming the successful modification of 2-(4-mercaptobutoxy)-1-naphthaldehyde oxime and Co3O4 supported AuNPs in a great experiment. In addition, differential pulse voltammetry further revealed that the developed electrochemical sensor exhibited excellent selectivity, sensitivity and stability in real samples analysis. Under optimal conditions, the modified sensor displayed a broad linear range from 1 × 10−14 M to 1 × 10−6 M with a fairly low detection limit of 8.4 × 10−14 M (S/N = 3) and was expected to act as a superior method for dimethoate determination.

Electrochemical biomimetic sensor based on oxime group-functionalized gold nanoparticles and nitrogen-doped graphene composites for highly selective and sensitive dimethoate determination

A novel, sensitive, and selective electrochemical sensor based on oxime-functionalized gold nanoparticles (AuNPs) and nitrogen-doped graphene (NG) composites (NG/AuNPs) was developed for the direct electrochemical detection of dimethoate, a non-electroactive organophosphorus pesticide (OP). 2-(4-Mercaptobutoxy)-1-naphthaldehyde oxime (MNO), a new organic molecule containing –SH and oxime synthesized by our group, was decorated onto electrodes through the S–Au bond between –SH of MNO and AuNPs. NG/AuNPs were modified on the electrode to provide acting sites for MNO and to amplify current response. The results indicated that the reduction current of MNO was increased, and the selectivity, sensitivity, and stability of the sensor were improved. Dimethoate was detected by using MNO as an electroactive probe through the nucleophilic substitution between oxime and dimethoate. Under optimal conditions, the sensor displayed a linear range from 1 × 10−12 to 4 × 10−8 M with a low detection limit of 8.7 × 10−13 M (S/N = 3). Results indicated that the sensor was successfully applied to detect dimethoate in water, tomato, and orange samples. Interference study analyses were investigated using the prepared electrode, which exhibited an acceptable result.

Determination of Dimethoate and Malathion Residues on and in Moloukhia Leaves

Determination of Dimethoate and Malathion Residues on and in Moloukhia Leaves

Double-imprinted potentiometric sensors based on ligand exchange for the determination of dimethoate

This paper describes a dimethoate imprinted polymeric potentiometric sensor for the determination of dimethoate that was designed by dispersing the dimethoate-imprinted polymer in dibutyl phthalate plasticizer and then embedded in polyvinyl chloride matrix. The method is based on molecularly imprinted polymer (MIP), which can be synthesized by using dimethoate as a template molecule, chitosan-Cd(II), and 3-mercaptopropyl-trimethoxysilane as a functional monomer and TEOS, and ephychlorohydrin as a cross-linking agent. We have studied a method for the selective binding behavior of dimethoate compounds on the surface of imprinted polymers which is prepared using ligand-exchange (LE) (chitosan-Cd(II)) monomer. The MIP-LE-1 and MIP-LE-2 based membranes have shown a detec- tion limit of 4.3×10 �6 mmolL �1 and 3.5.10 �5 mmolL �1 , respectively. The sensor has exhibited a response time of 35 min for MIP-LE-1 and 120 min for MIP-LE-2. They are stable for more than three months.

Selective determination of dimethoate via fluorescence resonance energy transfer between carbon dots and a dye-doped molecularly imprinted polymer

A novel molecularly imprinted fluorescent sensor was developed for dimethoate determination based on fluorescence resonance energy transfer. First, a doped molecular template polymer was prepared by electropolymerization. During dimethoate detection, a competitive reaction occurred between dimethoate and carbon dot labeled dimethoate. Fluorescence resonance energy transfer between residual carbon dots labeled dimethoate in the sensor and methyl red on the doped molecularly imprinted polymer then occurred, enhancing the fluorescence signal of the sensor. The fluorescence intensity decreased when the carbon dots labeled dimethoate molecules were replaced by dimethoate molecules in the samples. Under optimal conditions, good linear correlation was obtained for dimethoate over the concentration range from 6×10−10mol/L to 3.4×10−8mol/L with a detected limit of 1.83×10−11mol/L. This sensor was used to detect for dimethoate in actual samples, for which recoveries ranging from 95.0% to 106.0% were obtained.

Determination of dimethoate and phosmet pesticides with surface-enhanced Raman spectroscopy

ABSTRACTSurface-enhanced Raman spectroscopy spectra of dimethoate and phosmet pesticides were recorded using a Klarite substrate. Significant enhancements were achieved with dimethoate over a concentration range of 0.5–10 µg mL−1 and phosmet over a concentration range of 0.1–10 µg mL−1. The best prediction model for dimethoate pesticide was achieved with a correlation coefficient of 0.940 and a root mean square error of prediction of 0.864 µg mL−1, with the first derivative and standard normalized variate data preprocessing, and the best prediction model of phosmet pesticide was achieved with a correlation coefficient of 0.949 and a root mean square error of prediction of 0.741 µg mL−1 with the first derivative data preprocessing. Our study shows that pesticides, including dimethoate and phosmet, could be quantitatively measured at as low as 0.5 µg mL−1 level using surface-enhanced Raman technology coupled with a Klarite substrate and the results indicated that surface-enhanced Raman spectroscopy with a Klarite substrate has potential for the analysis of dimethoate and phosmet residues.

Determination of trace dimethoate in milk and river water by kinetic spectrophotometry using malachite green and potassium periodate

In the present study, a new sensitive and simple kinetic-spectrophotometric method for the determination of the insecticide dimethoate [O,O-dimethyl-S-(N-methyl-carbomoylmethyl)-phosphoro-dithioate] is developed. The method is based on the inhibition effect of dimethoate on the oxidation of malachite green (MG) by potassium periodate (KIO4) in the presence of Mn(II) ions. Inhibition kinetics of this catalytic reaction was investigated in the presence of dimethoate and the possibility of its analytical application was evaluated. The important variables that affected the reaction rate were investigated and the optimum conditions giving maximum sensitivity were established. Dimethoate was determined with linear calibration graph in the interval from 4.58 to 41.22 μg/mL. The optimized conditions yielded a theoretical detection limit of 1.24 μg/mL based on the 3S b criterion. The RSDs of the method (n = 5) were 1.2–4.9% for the concentration interval of dimethoate from 4.58 to 41.22 μg/mL. The reaction was monitored spectrophotometrically by measuring the change in absorbance over time at 615 nm. The method was applied to the determination of dimethoate in waters and milk, and was compared with the spectrophotometric method. The quantitive method developed on the basis of inhibition kinetics is practical, fast and economical. For this reason, it is open for new application fields.

Kinetics of dimethoate biodegradation in bacterial system

The present study is an investigation on the kinetics of dimethoate biodegradation and an estimation of residual dimethoate in bacterial culture by spectrophotometry. The methylene chloride extract of the culture medium was used for determination of dimethoate through its reaction with 1 chloro-2, 4 dinitrobenzene to produce methylamine whose absorbance at 505 nm gave an estimation of dimethoate content. The dimethoate standard curve follows Beer’s law at 505 nm with a slope of 0.0129 absorbance units per µg/mL. The regression equation relating concentration of dimethoate (x) with the absorbance is (y): y = 0.037 + 0.0129x. The amount of residual dimethoate after 7 days were 0, 4, 17, 28 and 29 µg/mL; the rate constants were 0.775, 0.305, 0.225, 0.167 and 0.127 each per day, and the efficiency of dimethoate degradation were 100%, 96%, 83%, 72% and 71%, for &lt;em&gt;Bacillus licheniformis, Pseudomonas aeruginosa, Aeromonas hydrophila, Proteus mirabilis &lt;/em&gt;and &lt;em&gt;Bacillus pumilus&lt;/em&gt; respectively. Dimethoate remediation could be attained through bacterial metabolism of the pesticide and colorimetric analysis might be useful in the estimation of dimethoate within a detection limit of 5-100 µg/mL.

Native vs photoinduced chemiluminescence in dimethoate determination

The determination of dimethoate using either its native chemiluminescent (CL) properties or its photoinduced chemiluminescence obtained by irradiation with a 15 W low-pressure mercury lamp was studied. Thereby, two flow injection systems (FIA) with and without irradiation were exhaustively optimized and their analytical characteristics studied. Better sensitivity and selectivity was found in absence of irradiation, due to the enhancing effect of hexadecylpyridinium chloride (HPC), which acted as a sensitizer. In the developed FIA-CL system, the alkaline hydrolysis of dimethoate with NaOH was performed on-line in presence of HPC. The oxidation of the product of hydrolysis with Ce(IV) in hydrochloric medium induced chemiluminescence. The method provided a limit of detection of only 0.05 ng mL −1 without any pre-treatment. However, the combination with solid phase extraction allowed the removal of some potential interferents as well as the preconcentration of the pesticide. Finally, the developed method was successfully applied to natural waters with recoveries between 95 and 108%.

Determination of dimethoate and omethoate in human serum samples. Risk assessment for the operator

A simple and effective analytical procedure has been developed for the determination of dimethoate (DIM) residues and its metabolite, omethoate, in serum samples of pesticide operators. For the selection of the most appropriate method for sample treatment, techniques such as headspace solid phase micro extraction and solid phase extraction and liquid–liquid extraction were applied. The applied method was based on toluene (2 mL) extraction of a 0.5 mL serum sample. In this report, it was observed that DIM concentration level affected the ratio of the area response of DIM and one of its oxygenated metabolite, omethoate. In this context, higher concentrations favoured the predominance of DIM while lower concentrations lead to the formation of omethoate. The method was validated using human serum samples spiked with DIM. Good linearity was obtained in the range of 1–10 ng/mL co-calculating DIM and omethoate. Various concentrations of DIM were mixed with serum and stored up to five days at −20°C. Recoveries ranged from 72% to 88% at two spiking levels for six replicates. The detection and quantification limit were calculated at 0.12 and 0.36 ng/mL of serum, respectively. Finally the comparison with the Acceptable Operator Exposure Level (AOEL) of DIM revealed that the maximum exposure of the operators reached the 30% of the AOEL for only two cases.