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Herein, we propose rapid, precise acetylcholinesterase (AChE) inhibition-based sensing strategy for malathion detection in the presence of Ag-GO and acetylthiocholine (ATCh). The biosensing method was developed with a nanocomposite of citrate stabilized AgNPs anchored on the GO sheets (Ag-GO). The physical and chemical properties of the prepared Ag-GO composite were analyzed with various characterization techniques, including XRD, FT-IR, XPS, UV–Visible spectroscopy, and HR-TEM. The positively charged thiocholine (TCh) produced by enzyme hydrolysis triggers the AgNPs aggregation on GO sheets, which ultimately decreases the intensity of the corresponding SPR absorption peak. While the addition of malathion into the sensing system hindered the AChE activity and limited the TCh production, and thus inhibits the decrease in the SPR band intensity. The designed sensing system displayed linearity in the broad range of malathion concentrations (0.01 pM–1000 pM) with a limit of detection and the limit of quantification values of 0.01 pM, and 0.035 pM, respectively. The application of the designed biosensing system was extended to determine the malathion in actual samples namely, tap water, agricultural runoff water, lake water, and grape extract, which resulted in almost 100% recovery rates in all the spiked samples. Image 1 • AChE inhibition based sensing strategy for malathion detection was developed. • Colorimetric detection of malathion by Ag-GO nanocomposite was employed. • The designed biosensor displayed linearity in the wide range, 0.01 pM–1000 pM. • The LOD and LOQ values of proposed method were 0.01 pM and 0.035 pM, respectively. [ABSTRACT FROM AUTHOR]

In this work, copper oxide nanoparticles (CuONPs) nanozymes paper-based analytical device was designed for the rapid detection of organophosphate pesticides in fruits and vegetables. The paper-based analytical device was modified with silica oxide nanoparticles to enhance the assay sensitivity. CuO nanozymes displayed peroxidase-like activity and catalyzed the oxidation of o -dianisidine in the presence of H 2 O 2 from the hydrolysis of acetylthiocholine. This results in the formation of a brown−colored product. In the presence of organophosphate pesticides such as malathion, acetylcholinesterase activity was inhibited, resulting in reduced color intensity production, and which was measured with a smartphone. The proposed nanozymes paper-based analytical device exhibited a good linear detection range (0.1–5 mg L−1), a low detection limit of 0.08 mg L−1, and the analysis time was only about 10 min for malathion detection under optimal conditions. Moreover, the CuONPs had excellent catalytic activity and higher stability than peroxidase. Finally, this device can be applied to detect organophosphate pesticides in fruits and vegetables with rapidity, accuracy, portability, and ease of handling in the field. [Display omitted] • A nanozymes paper−based analytical device is constructed for organophosphate pesticides detection in fruits and vegetables. • CuONPs is used as nanoenzyme platform with biosensor technique to detect organophosphate pesticides. • The proposed device presented detection sensitivity, portability and the ability for real samples detection. [ABSTRACT FROM AUTHOR]

A highly sensitive acetylcholinesterase (AChE) electrochemical biosensor for the quantitative determination of organophosphate pesticides (OPs) in vegetables and fruits based on palladium-copper nanowires (Pd-Cu NWs) was reported. AChE immobilized on the modified electrode could catalyze hydrolysis of acetylthiocholine chloride (ATCl), generating an irreversible oxidation peak. When exposed to the OPs, the activity of the AChE was inhibited and the current significantly decreased. The detection mechanism is based on the inhibition of AChE. The Pd-Cu NWs not only provide a large active surface area (0.268 ± 0.01) cm 2 for the immobilization of AChE, which was approximately 3.8 times higher than the bare glass carbon electrode, but also exhibit excellent electro-catalytic activity and remarkable electron mobility. The biosensor modified with Pd-Cu NWs displayed a good affinity to ATCl and catalyzed hydrolysis of ATCl, with a low Michaelis–Menten constant ( K M ) of 50.56 μM. Under optimized conditions, the AChE-Cs/Pd-Cu NWs/GCE biosensor detected malathion with wide linear ranges of 5–1000 ppt and 500–3000 ppb, and the low detection limit was 1.5 ppt (4.5 pM). In addition, the OPs biosensor has been applied to the analysis of malathion in commercial vegetable and fruit samples, with excellent recoveries in the range of 98.5%–113.5%. This work provides a simple, sensitive and effective platform for biosensors and exhibits future potential in practical application for the OPs assay. [ABSTRACT FROM AUTHOR]

An electrochemical aptasensor based on chitosan-iron oxide nanocomposite (CHIT-IO) film deposited on fluorine tin Oxide (FTO) was developed for the detection of malathion. Iron oxide nanoparticles were prepared by co-precipitation method and characterized by Transmission electron microscopy and UV–Visible spectroscopy. The biotinylated DNA aptamer sequence specific to the malathion was immobilized onto the iron oxide doped-chitosan/FTO electrode by using streptavidin as linking molecule. Various characterization studies like Field Emission-Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and Electrochemical studies were performed to attest the successful fabrication of bioelectrodes. Experimental parameters like aptamer concentration, response time, stability of electrode and reusability studies were optimized. Aptamer immobilized chitosan-iron oxide nanocomposite (APT/SA/CHIT-IO/FTO) bioelectrodes exhibited LOD of about 0.001 ng/mL within 15 min and spike-in studies revealed about 80–92% recovery of malathion from the lettuce leaves and soil sample. [ABSTRACT FROM AUTHOR]

In this work, a multiplexed electrochemical aptasensor based on mixed valence Ce-MOF was constructed for the simultaneous determination of malathion and chlorpyrifos. Firstly, Ce(III, IV)-MOF materials with many catalytic sites were synthesized and characterized by SEM, TEM, XPS, FT-IR, XRD, and UV–Vis. Then, the chlorpyrifos and malathion signal markers based on Ce(III, IV)-MOF were prepared using thionine (Thi) and ferrocene (Fc) used as the electrochemical probe. The electrochemical signal was amplified by the reduction of thionine catalyzed by the spontaneous cycle of Ce(III, IV) in Ce(III, IV)-MOF skeleton and the reduction of ferrocene catalyzed by ascorbic acid (AA) in solution. The detection of the two targets did not interfere with each other, and the quantitative detection was realized with high sensitivity. The detection range of chlorpyrifos and malathion were 1.0 μM ∼ 0.1 pM, and the detection limits of chlorpyrifos and malathion were 0.038 and 0.045 pM (S/N = 3), respectively. The sensor provided a new idea for the simultaneous determination of multi-component and had a high application prospect in the field of food safety in the future. [Display omitted] • A multiplexed aptasensor for simultaneous detection of chlorpyrifos and malathion was established. • The prepared mixed valence Ce-MOF had good catalytic effect on the Thi. • Thi and Fc generate electrochemical signals at different potentials for simultaneous detection of two pesticides. [ABSTRACT FROM AUTHOR]

ABSTRACT: Aptamers are single-stranded DNA or RNA that can specifically bind to a target substance with high affinity. Pesticides have obvious biological effects and are very harmful to the human body and the environment. Surface-enhanced Raman spectroscopy (SERS) can be combined with aptamer for the rapid detection of pesticide residues because of its simple operation and high sensitivity. However, a single analysis method has certain limitations and can't satisfy the research of complex system. In this study, SERS and electrochemical were used to prove the specific recognition of malathion by aptamer. The biochemical sensor directly detected the SERS spectra of the aptamer, malathion, and aptamer-malathion through the SERS method. Malathion could also be verified the specific recognition of aptamer by differential pulse voltammetry (DPV) and cyclic voltammetry (CV). Based on the peak difference before and after the combination of malathion and aptamer, a detection method for the specific recognition of malathion in a complex system was established. The identification mechanism was discussed. Then, the practical detection of malathion demonstrated the practicability of the method. The method was applied for the detection of malathion in spiked apple and bell pepper samples. The recoveries were in the range of 89.80%–106.50%, and the relative standard deviations were from 2.51%–6.92%. The use of aptamers for the specific detection of pesticides will have the potential for broad applications in the future. • Electrochemistry and surface-enhanced Raman spectroscopy were combined to specifically recognize malathion by the aptamer. • induce silver nanoparticles to form Calcium ions were used as aggregating agents to induce silver nanoparticles to form "hot spots". • A method for the detection of practical complex samples was established. • The aptamer-based sensor exhibited favorable selectivity, reliability, and stability in spiked samples. [ABSTRACT FROM AUTHOR]

An analytical methodology was developed for detection of malathion in the peels of tomatoes and Damson plums by surface-enhanced Raman imaging spectroscopy and multivariate curve resolution. To recover the pure spectra and the distribution mapping of the analyzed surfaces, non-negative matrix factorization (NMF), multivariate curve calibration methods with alternating least squares (MCR-ALS) and MCR with weighted alternating least square (MCR-WALS) were utilized. Error covariance matrices were estimated to evaluate the structure of the error over all the data. For the tomato data, NMF-ALS and MCR-ALS presented excellent spectral recovery even in the absence of initial knowledge of the pesticide spectrum. For the Damson plum data, owing to heteroscedastic noise, MCR-WALS produced better results. This methodology enabled detection below to the maximum residue limit permitted for this pesticide. This approach can be implemented for in situ monitoring because it is fast and does not require extensive manipulation of samples, making its use feasible for other fruits and pesticides as well. [ABSTRACT FROM AUTHOR]

Abstract: Luminescence quenching of a novel long lived Eu(III)–pyridine-2,6-dicarboxylic acid probe of 1:2 stoichiometric ratio has been studied in 0.10 volume fraction ethanol–water mixture at pH 7.5 (HEPES buffer) in the presence of the organophosphorus pesticides chlorfenvinphos (P1), malathion (P2), azinphos (P3), and paraxon ethyl (P4). The luminescence intensity of Eu(III)–(PDCA)2 probe decreases as the concentration of the pesticide increases. It was observed that the quenching due to P3 and P4 proceeds via both diffusional and static quenching processes. Direct methods for the determination of the pesticides under investigation have been developed using the luminescence quenching of Eu(III)–pyridine-2,6-dicarboxylic acid probe in solution. The linear range for determination of the selected pesticides is 1.0–35.0μM. The detection limits were 0.24–0.55μM for P3, P4, and P1 and 2.5μM for P2, respectively. The binding constants (K), and thermodynamic parameters of the OPs with Eu(III)–(PDCA)2 were evaluated. Positive and negative values of entropy (ΔS) and enthalpy (ΔH) changes for Eu(III)–(PDCA)2–P1 ternary complex were calculated. As the waters in this study do not contain the above mentioned OPs over the limit detectable by the method, a recovery study was carried out after the addition of the adequate amounts of the organophosphorus pesticides under investigation. [Copyright &y& Elsevier]

Abstract: A novel sample pre-treatment technique termed dispersive suspended microextraction (DSME) coupled with gas chromatography-flame photometric detection (GC-FPD) has been developed for the determination of eight organophosphorus pesticides (ethoprophos, malathion, chlorpyrifos, isocarbophos, methidathion, fenamiphos, profenofos, triazophos) in aqueous samples. In this method, both extraction and two phases’ separation process were performed by the assistance of magnetic stirring. After separating the two phases, 1μL of the suspended phase was injected into GC for further instrument analysis. Varieties of experiment factors which could affect the experiment results were optimized and the following were selected: 12.0μL p-xylene was selected as extraction solvent, extraction speed was 1200rpm, extraction time was 30s, the restoration speed was 800rpm, the restoration time was 8min, and no salt was added. Under the optimum conditions, limits of detections (LODs) varied between 0.01 and 0.05μgL−1. The relative standard deviation (RSDs, n =6) ranged from 4.6% to 12.1%. The linearity was obtained by five points in the concentration range of 0.1–100.0μgL−1. Correlation coefficients (r) varied from 0.9964 to 0.9995. The enrichment factors (EFs) were between 206 and 243. In the final experiment, the developed method has been successfully applied to the determination of organophosphorus pesticides in wine and tap water samples and the obtained recoveries were between 83.8% and 101.3%. Compared with other pre-treatment methods, DSME has its own features and could achieve satisfied results for the analysis of trace components in complicated matrices. [Copyright &y& Elsevier]

Abstract: Pesticides are toxic substances and may cause unintentional harm if improperly used. The ubiquitous nature of pesticides, with frequent use in agriculture and the household, and the potential for harm that pesticides pose to non-target organisms such as wildlife, humans, and pets, demonstrate the need for rapid and effective detection and identification of these compounds. In this study, single particle aerosol mass spectrometry (SPAMS) was used to rapidly detect compounds from four classes of pesticides commonly used in agricultural and household applications. These include permethrin (pyrethroid class), malathion and dichlorvos (organophosphate class), imidacloprid (chloronicotinyl class), and carbaryl (carbamate class). Analytical standards of each compound were diluted and aerosolized using a nebulizer to create particles for analysis in the SPAMS instrument. The resultant dual-polarity time-of-flight mass spectra were then analyzed to identify the characteristic peaks of the compound in each sample. In addition, samples of commercial products containing pesticides, a commercial insecticide spray, containing permethrin, and a canine flea collar, containing carbaryl, were analyzed in their original form using SPAMS without any significant sample preparation. The characteristic mass spectral peaks of the active pesticides in these samples were identified using the mass spectra obtained earlier from the pesticide analytical standards. By successfully identifying pesticides in analytical standards and in commercial products, it is demonstrated herein that the SPAMS system may be capable of pesticide detection in numerous environmental and agricultural situations. [Copyright &y& Elsevier]

Abstract: Double stranded calf thymus deoxyribonucleic acid entrapped polypyrrole-polyvinyl sulphonate (dsCT-DNA-PPy-PVS) films fabricated onto indium-tin-oxide (ITO) coated glass plates have been used to detect organophosphates such as chlorpyrifos and malathion. These disposable dsCT-DNA-PPy-PVS/ITO bioelectrodes have been characterized using cyclic voltammetry, Fourier-transform-infra-red (FTIR) spectroscopy and atomic force microscopy (AFM), respectively. These biosensing electrodes have a response time of 30s, are stable for about 5 months when stored in desiccated conditions at 25°C and can be used to amperometrically detect chlorpyrifos (0.0016–0.025ppm) and malathion (0.17–5.0), respectively. The additive effect of these pesticides on the amperometric response of the disposable dsCT-DNA-PPy-PVS/ITO bioelectrodes has also been investigated. [Copyright &y& Elsevier]

Abstract: Sensitive, simple and rapid ELISA methods have been developed for the determination of four organophosphorus pesticides in extra virgin olive oil. The analytical procedure involves simultaneous extraction of the analytes from oil matrix with methanol and a freezing clean-up step (−80°C), followed by immunoassay determination using standards in matrix. The methodology is specific for diazinon, fenthion, malathion and chlorpyrifos showing little or no cross-reactivity against other organophosphorus compounds. Limits of detection for the pesticides in olive oil are from 46ngml−1 for diazinon to 10ngml−1 for fenthion, all of them under the established MRLs for olives. The excellent recoveries (between 94 and 122%) obtained by the complete analytical protocol confirm the potential of this approach for detecting these compounds in olive oil, being useful as screening and complementary method in pesticide regulatory and food safety programs. The proposed methodology also correlates well with the reference chromatographic (GC–MS) methods. [Copyright &y& Elsevier]

Abstract: Possibilities of on-line non-contact detection of the vapour of the commercially available pesticide malathion by the CO2 laser were investigated, using a photoacoustic technique developed in our laboratory. A set of laser/vapour spectral coincidences in the usual range of CO2 laser wavelengths were obtained, the samples being: the commercial product Etiol available on the market, solvent, emulsifiers, and neat malathion, all with air added to a mid-pressure of about 100mbar and to atmospheric pressure. Relative contributions of the components in the product are discussed. A detection limit of 0.002vol.% of the product in air was estimated. [Copyright &y& Elsevier]

Abstract: The separation of the enantiomers of a group of organophosphorus pesticides (OPs) has been investigated by electrokinetic chromatography (EKC) using different anionic cyclodextrins as chiral selectors. The use of a 25mM Tris buffer (pH 7.0), 20mM in CM-β-CD together with an applied voltage of 24kV and a temperature of 25°C enabled the individual enantiomeric separation of malathion and phenthoate each one into its two enantiomers, the partial separation of the enantiomers of phenamiphos and the separation of three of the four enantiomers of isomalathion. Since naled is very reactive in aqueous solutions, its enantiomeric separation achieved in about 8min in 25mM borate buffer at pH 9 with 10mM CM-β-CD resulted in the observation of a broad peak due to degradation products. A preconcentration step by disk solid-phase extraction was studied and used together with the chiral EKC method developed for the enantiomeric separation of malathion in order to determine this pesticide in tap water samples spiked at the μgmL−1 level. Finally, the precision and recovery of the method was established. [Copyright &y& Elsevier]

Abstract: A method to selectively generate vapor signatures from malathion entrained within matrices of surface-impacted aerosol particles has been demonstrated. The method uses ultraviolet radiation (172 or 222nm) from a continuous wave discharge lamp to photodissociate malathion molecules collected within and on surface-impacted particles, followed by detection via ion mobility spectrometry (IMS). Since surface heating does not occur, only those molecules whose photofragments exhibit high vapor pressure are introduced into the IMS instrument and then only those exhibiting high proton affinity are subsequently detected. This process produces less signal clutter than in pyrolysis-IMS, where the background aerosol is pyrolyzed along with the sample. Quantities of malathion as small as 50ng could be detected when the malathion was entrained on a clean surface, and as small as 100ng when co-entrained on a surface with much larger quantities of background aerosols such as diesel soot, road dust, Bacillus globigii, albumin, and cotton lint. This sensitivity indicates that, when combined with a particle collector as an effective pre-concentrator, detection of malathion aerosol concentrations of <0.01mg/m3 will be possible. Since malathion can be viewed as a model compound, this technique is also extendable to the detection of organophosphate war chemicals. [Copyright &y& Elsevier]

An environmentally friendly methodology has been developed for quality control analysis of emulsifiable concentrate pesticide formulations containing Malathion as active ingredient, using flow injection analysis (FIA)–Fourier transform infrared (FTIR) spectrometry. Five microlitres samples were directly injected into a 3 ml closed FIA manifold, in which 2 ml of CHCl3 was re-circulated at 1.96 ml min−1. After homogenisation and sample measurement, 2 μl volumes of a Malathion standard were injected, taking absorbance measurements after each injection. Peak height of the chemigrams, established from peak area values between 1027 and 1017 cm−1, corrected with a baseline fixed from 1087 to 993 cm−1 were employed for Malathion quantification using the standard addition approach, after reaching the steady state for every injection. A limit of detection of 12 μg ml−1 was achieved. Results found by standard addition-FTIR in commercially available samples showed a good correlation with those obtained by the reference gas chromatography-flame ionisation detection procedure. [Copyright &y& Elsevier]