Detection Of Organophosphates Research Articles

Real-time, specific, and label-free transistor-based sensing of organophosphates in liquid

Organophosphates (OP), commonly used in agriculture and as chemical warfare agents, pose significant environmental risks, necessitating real-time, low-cost OP detection methods. In particular, liquid-phase OP sensing with minimal sample volumes is crucial. While several methods allow rapid detection of low concentrations of OP vapors, they are effective only in the short term, while vapors are still being produced. Many OP compounds are semi-volatile, leading to the contamination of water, soil, and surfaces, posing a risk of secondary, long-term exposure. Detecting this contamination requires methods that can be directly applied to droplets of the affected medium. Currently, no method provides the desired combination of ultra-sensitivity, quantitative detection, rapid response, and low-cost for detecting OPs in liquid samples. This study aims to demonstrate quantitative, low-cost, real-time, specific, and label-free OP sensing in ultra-small samples using a transistor-based approach. The current work employs the 2-(4-Aminophenyl)-1,1,1,3,3,3-hexafluoro-2-propanol (aminophenyl-HFIP) functionalized meta-nano-channel field-effect chemical sensor (MNChem sensor) to monitor the organophosphate, diethyl cyanophosphonate (DCNP), in liquid samples. The silicon component of the MNChem is fabricated using a complementary metal-oxide semiconductor (CMOS) process, and the amine-based chemical functionalization of the sensing area is performed post-fabrication. The MNChem sensor provides electrostatic control over the source-drain current (IDS), allowing an optimized channel configuration that efficiently transduces localized OP recognition events into significant IDS variations. Sensing is performed using 0.5 μL buffer solution to simulate a miniature field-deployable sensor for on-site liquid analysis. We report the sensing of DCNP with a limit-of-detection of 100 fg/mL, a dynamic range of 9 orders of magnitude, and excellent linearity (≥0.97) and sensitivity. Control measurements confirm the specificity and reliability of the sensor's response, validating its applicability. This study introduces a novel method for OP detection in contaminated droplets using a low-cost disposable transistor technology.

High-sensitive detection of organophosphate and carbamate pesticide residues in milk based on bioluminescence method

Organophosphorus pesticides (OPs) and carbamate pesticides (CBs) are the most commonly used pesticides in agricultural cultivation. The pesticide residues in plant products can easily enter dairy cows through feed, resulting in the pesticide low-concentration residues in milk. Traditional acetylcholinesterase (AChE) inhibition-based colorimetric methods have low sensitivity and could not satisfy the detection of low-concentrations of OPs and CBs residues in dairy products. In this study, we combined firefly luciferase (FLuc)-mediated bioluminescence with the inhibition of AChE-catalyzed substrate activity by pesticides to develop a highly sensitive and rapid method for detecting OPs and CBs residues in milk. AChE breaks down D-luciferin acetate to produce D-luciferin, which is recognized by the FLuc and emits luminescence in the presence of ATP. However, the presence of OPs and CBs inhibits AChE, causing the reduction or disappearance of the luminescence signal. The luminescence signal can be detected using a hand-held luminescence photometer, eliminating the need for large instrumentation. The AChE-FLuc system accurately detected OPs and CBs in milk within 30 min, with detection limits of 7.89 ng/mL and 1.75 ng/mL, respectively. The sensitivity of this method is approximately ten times higher than that of traditional AChE inhibition methods, meeting the pesticide residue limits in milk set by China and the European Union.

Seasonal Variability of Pesticide Residues in Vellode Bird Sanctuary: Implications for Ecosystem Health

This research provides a comprehensive examination of the seasonal fluctuations in pesticide residues within the Vellode Bird Sanctuary, with a particular emphasis on the detection and quantification of organochlorines, organophosphates, synthetic pyrethroids, and herbicides in the sanctuary's aquatic environment. The pesticide analysis was conducted from July 2019 to May 2020. This study period spanned three seasons: monsoon, winter, and summer. Gas Chromatography-Mass Spectrometry (GC-MS) from Perkin Elmer was used to analyze the pesticide residues in lake water. The pesticide analysis showed that aldrin, α-cypermethrin, α-HCH, β-HCH, bifenthrin, butachlor, chlorpyrifos, dimethoate, endosulfan-α, γ-HCH, pendimethalin, phorate, profenophos, p,p'-DDT, and quinalphos were recorded at higher levels during the monsoon season. The values of pesticide residues in the winter and summer seasons were below the level of detectable quantification (less than 0.5 μg/l). The study shows that increased pesticide concentrations during the monsoon are due to runoff from nearby agricultural fields caused by heavy rainfall. In contrast, lower pesticide levels in winter and summer are likely due to reduced pesticide use and rainfall. These findings highlight the significant impact of seasonal variations on pesticide contamination, with greater ecological risks during the monsoon. The sanctuary's aquatic ecosystem is particularly vulnerable during periods of high rainfall, emphasizing the need for targeted conservation and management strategies.

Organophosphate Detection in Animal-Derived Foods Using a Modified Quick, Easy, Cheap, Effective, Rugged, and Safe Method with Liquid Chromatography-Mass Spectrometry.

Organophosphates are widely used in the livestock industry. In this study, we developed a method for detecting 27 organophosphate insecticides in animal-derived foods, including beef, pork, chicken, milk, and eggs, using liquid chromatography-tandem mass spectrometry. A modified QuEChERS method was optimized for sample pretreatment. A mixture of acetonitrile and acetone was used as the extraction solvent, and MgSO4 and NaCl were used as salts. Among the five different dispersive solid-phase extraction systems, MgSO4, primary secondary amines, and C18 were selected for purification because they had the highest recovery rates and least matrix effects. The matrix-dependent limit of quantitation was 0.0005-0.005 mg/kg, and the correlation coefficient of the matrix-matched calibration curve was >0.99, which was acceptable for quantifying residues below 0.01 mg/kg-the default maximum residue limit in a positive list system. The recovery efficiencies ranged from 71.9 to 110.5%, with standard deviations ranging from 0.2% to 12.5%, satisfying the SANTE guidelines. The established analytical method was used to monitor organophosphates in animal-derived foods obtained from a local market, and no pesticides were detected. With respect to industry standards, our proposed method is recommended for practical organophosphate detection in animal-derived foods.

Advancing micro-electrometric techniques for the detection of organophosphate and carbamate residues using cricket cholinesterase.

The widespread use of organophosphate (OP) and carbamate (CM) pesticides requires efficient and cost-effective detection methods. This study introduces a micro-electrometric method using cricket cholinesterase (ChE) to detect OP and CM residues, providing a rapid and economical alternative to conventional chromatographic techniques. The parameters of the method, including the substrate concentration, incubation temperature, and incubation time, were optimized. By leveraging the sensitivity of cricket ChE to OP and CM inhibition, this approach translates enzyme inhibition into an electrical signal to quantify pesticide levels, achieving an impressive limit of detection (LOD) from 0.036 to 0.086 parts per million (ppm). This method demonstrated reproducibility and stability, making it suitable for field applications and on-site testing across various environmental matrices. This research represents a significant advancement in pesticide residue analysis with potential applications in the development of portable biosensor devices for real-time environmental monitoring and public health protection.

Emerging Technologies for Sensitive Detection of Organophosphate Pesticides: A Review

Abstract: The use of organophosphate pesticides (OPPs) in agricultural practices improves crop yield and controls pests, but their indiscriminate use and persistence in the environment pose significant health risks. Therefore, it has become increasingly important to develop reliable and efficient detection methods for OPPs to ensure food safety and monitor their presence. In recent years, OPP detection methods have undergone significant advancements. Sensors such as colorimetric, fluorescence, electrochemical, and impedometric offer several advantages over traditional methods, such as high sensitivity, selectivity, and portability. The purpose of this review paper is to provide an overview of recent developments in OPP detection methods. The paper discusses the different types of sensors that are available for the detection of OPPs, as well as their advantages and disadvantages. Many electrochemical methods have been employed to investigate OPP detection, including voltammetry, impedance spectroscopy, and amperometry. The integration of nanomaterials, such as carbon nanotubes, graphene, and metal nanoparticles, has significantly enhanced the performance of electrochemical sensors by providing high surface area, enhanced electron transfer, and specific analyte interactions. Furthermore, the review discusses the utilization of biomolecules, such as enzymes and aptamers, as recognition elements in sensor platforms for selective and sensitive OPP detection. The incorporation of these biomolecules offers high specificity and enables real-time monitoring of OPP residues in food samples and environmental matrices. It emphasizes the importance of continued research and development to optimize detection methods, improve sensor performance, and make these technologies more widely accessible for effective monitoring and control of OPP contamination in various domains.

Photoelectrochemical Solution Gated Graphene Field-Effect Transistor Functionalized by Enzymatic Cascade Reaction for Organophosphate Detection.

Solution Gated Graphene Field-Effect Transistors (SGGT) are eagerly anticipated as an amplification platform for fabricating advanced ultra-sensitive sensors, allowing significant modulation of the drain current with minimal gate voltage. However, few studies have focused on light-matter interplay gating control for SGGT. Herein, this challenge is addressed by creating an innovative photoelectrochemical solution-gated graphene field-effect transistor (PEC-SGGT) functionalized with enzyme cascade reactions (ECR) for Organophosphorus (OPs) detection. The ECR system, consisting of acetylcholinesterase (AChE) and CuBTC nanomimetic enzymes, selectively recognizes OPs and forms o-phenylenediamine (oPD) oligomers sediment on the PEC electrode, with layer thickness related to the OPs concentration, demonstrating time-integrated amplification. Under light stimulation, the additional photovoltage generated on the PEC gate electrode is influenced by the oPD oligomers sediment layer, creating a differentiated voltage distribution along the gate path. PEC-SGGT, inherently equipped with built-in amplification circuits, sensitively captures gate voltage changes and delivers output with an impressive thousandfold current gain. The seamless integration of these three amplification modes in this advanced sensor allows a good linear range and highly sensitive detection of OPs, with a detection limit as low as 0.05pm. This work provides a proof-of-concept for the feasibility of light-assisted functionalized gate-controlled PEC-SGGT for small molecule detection.

Zr-based metalloporphyrin MOF probe for electrochemical detection of parathion-methyl

An electrochemical (EC) sensor based on metalloporphyrin metal-organic framework (MOF) for the detection of parathion-methyl (PM) has been developed. The prepared MOF-525(Fe) exhibits great signal enhancement toward the electrochemical detection of PM owing to its unique structural properties and electrochemical activities. Under optimal experimental conditions, the as-prepared MOF-525(Fe) based EC sensor exhibited excellent PM sensing performance with a wide linear detection range (0.1 μM–100 μM) and low limit of detection (LOD, 1.4 nM). Compared to its corresponding Fe metalloporphyrin (linker), MOF-525(Fe) exhibited a superior sensitivity (28.31 μA cm−2·μM−1), which is 3.7 times higher than the sensitivity of FeTCPP linker (7.56 μA cm−2·μM−1) towards PM. The improved performance is associated with the high specific surface area and the large pore channels of MOF-525(Fe) facilitating a better interaction between PM and the Fe metalloporphyrin active sites, especially in the lower concentration range. Moreover, a possible affinity of the PM molecules toward Zr6 clusters may also contribute to the selective enrichment of PM on MOF-525(Fe). This EC sensor further demonstrated high selectivity in the presence of interfering molecules. The recovery results further confirm accurate PM sensing in actual samples, which suggests promising applications for the rapid detection of environmental organophosphates by metalloporphyrin MOFs.

Characterization and optimization of a quantitative colorimetric acetylcholine esterase inhibition assay for biochip integration demonstrated by neurotoxicity evaluation of malathion

Organophosphates (OPs) and carbamates as insecticides, nematicides, fungicides, and herbicides are constantly increasing. Their neurotoxic nature requires careful usage, and misuse can lead to fatalities. OPs classified as 'Class 1′ toxic compounds irreversibly inhibit cholinesterases due to their molecular structure resembling the natural acetylcholine substrate, leading to toxic events in the human brain. Monitoring such chemicals is relevant for agricultural applications and essential for the military sector to ensure the safety of personnel and civilian populations. State-of-the-art analytical detection methods require time-consuming pre-treatments and costly reagents and face challenges associated with pesticide properties like thermal lability, low volatility, and high polarity, which can compromise analysis performance. Advanced systems like electrophoresis or liquid chromatography are used to address these, but these are not well suited for field analysis. Miniaturized colorimetric assays are becoming more popular for various portable devices and kits (i.e., metabolic or blood cell assays) due to their ease of use and practicality. Here, we aimed to establish and optimize a straight-forward paper-based microfluidic acetylcholine esterase inhibition assay for mobile organophosphate detection, laying the groundwork for future microdevice modules to be used in environmental monitoring, public health, and CBRN applications.

Highly selective sensing of organophosphate pesticides based on a Dual-Detection 3D Paper-Based microfluidic platform

A dual detection platform including colorimetry and LDI-MS was implemented with a 3D paper-based analytical device (PAD) for highly selective and sensitive detection of organophosphates (OPs). The colorimetric approach based on the inhibition assay of acetylcholinesterase (AChE) activity by OPs was employed for preliminary testing/screening of the presence of OPs and performing quantitative analysis of total OPs. Limit of detections (LODs) from colorimetric assay were 0.006 and 0.01 mg L−1 for dichlorvos and paraoxon, respectively, which were sufficient to monitor the OPs at the maximum residues levels (MRLs). However, LDI-MS as a complementary detection technique was further exploited to differentiate the type of OPs and quantify the amount of individual OPs at trace concentrations. With LDI-MS, the detection sensitivity was enhanced with extremely low LODs of 5 µg/L for both dichlorvos and paraoxon. This dual detection platform has shown its performance for determination of dichlorvos and paraoxon in cabbage, broccoli and grape with satisfied accuracy and precision.

Follicular DNA Damage and Pesticide Exposure Among Latinx Children in Rural and Urban Communities

The intersectional risks of children in United States immigrant communities include environmental exposures. Pesticide exposures and their biological outcomes are not well characterized in this population group. We assessed pesticide exposure and related these exposures to DNA double-strand breaks (DSBs) in Latinx children from rural, farmworker families (FW; N = 30) and from urban, non-farmworker families (NFW; N = 15) living in North Carolina. DSBs were quantified in hair follicular cells by immunostaining of 53BP1, and exposure to 72 pesticides and pesticide degradation products were determined using silicone wristbands. Cholinesterase activity was measured in blood samples. DSB frequencies were higher in FW compared to NFW children. Seasonal effects were detected in the FW group, with highest DNA damage levels in April–June and lowest levels in October–November. Acetylcholinesterase depression had the same seasonality and correlated with follicular DNA damage. Organophosphate pesticides were more frequently detected in FW than in NFW children. Participants with organophosphate detections had increased follicular DNA damage compared to participants without organophosphate detection. Follicular DNA damage did not correlate with organochlorine or pyrethroid detections and was not associated with the total number of pesticides detected in the wristbands. These results point to rural disparities in pesticide exposures and their outcomes in children from vulnerable immigrant communities. They suggest that among the different classes of pesticides, organophosphates have the strongest genotoxic effects. Assessing pesticide exposures and their consequences at the individual level is key to environmental surveillance programs. To this end, the minimally invasive combined approach used here is particularly well suited for children.

Competitive Assay for the Ultrasensitive Detection of Organophosphate Pesticides Based on a Fiber-Optic Particle Plasmon Resonance Biosensor and an Acetylcholinesterase Binding Peptide.

An acetylcholinesterase (AChE) binding-based biosensor was developed for the ultrasensitive detection of organophosphate (OP) pesticides. The biosensor integrates the technique based on fiber-optic particle plasmon resonance detection and a synthetic AChE binding peptide conjugated with gold nanoparticles on the optical fiber surface via an AChE competitive binding assay. The OP pesticides present in the solution hinder the binding of AChE to the peptide on the biosensor by competing for the binding sites present in AChE. The limit of detection obtained for parathion using this method was observed to be 0.66 ppt (2.3 pM). This method shows a wide linear dynamic range of 6 orders. Furthermore, the use of the AChE binding peptide in the biosensor can better discriminate OPs against carbamates by using only a single biosensor. The practical application of this method was tested using spiked samples, which yielded good recovery and reproducibility. The spiked sample required minimal pretreatment before analysis; hence, this biosensor may also be used in the field.

An electrochemical AChE-based biosensor for organophosphate pesticides using a modified CuNWs/rGO nanocomposite on a screen-printed carbon electrode

An enzymatic electrochemical biosensor was built for the indirect detection of organophosphates (OPs), based on acetylcholinesterase inhibition. The biosensor was fabricated for enhanced performance on a screen-printed carbon electrode (SPCE), modified with copper nanowires (CuNWs) composited with reduced graphene oxide (rGO). The oxidation current was measured using the cyclic voltammogram (CV) method, as generated by the enzymatic interaction between acetylcholinesterase (AChE) and its substrate, acetylthiocholine (ATCh). The biosensing response is the reduction in signal caused by the inhibition of acetylcholinesterase in the presence of an organophosphate inhibitor. Benchmarking shows that the CuNWs/rGO nanocomposite enhanced the signal current considerably and decreased the oxidation potential for electrochemical detection of the OP chlorpyrifos, exhibiting a wide linear detection rangefrom 10 µg/L–200 µg/L, with a limit of detection of 3.1 µg/L and limit of quantification of 12.5 µg/L. This sensor is useful for the analysis of chlorpyrifosin drinking water and orange juice, with high recovery rates and no interference effects.

Versatile sensing capabilities of layer-by-layer deposited polyaniline-reduced graphene oxide composite-based sensors

Precise temperature, humidity, and organic pollutants monitoring are required for industrial, environmental and medical applications. The interesting properties of polyaniline for sensors, such as environmental responsiveness and stability, combined with the large surface area and tunable properties of graphene oxide, offer excellent prospects for the development of sensor materials. In this paper, we show that HCl-doped polyaniline/reduced graphene oxide (PANI/rGO) layer-by-layer deposition and subsequent reduction can be used as resistive sensors for temperature, humidity, acetone, and electrochemical sensors for organophosphate detection in aqueous solutions. Sensors were characterized using atomic force and scanning electron microscopies and energy-dispersive x-ray and Raman spectroscopies, and impedance spectroscopy complemented by semi-empirical quantum chemical calculations. Reduction temperature and bilayer numbers influence PANI/rGO sensor characteristics significantly. The results show that only one PANI/rGO bilayer is needed to provide a temperature coefficient of resistance of − 0.758 °C−1 and 37% sensitivity at 95% relative humidity. PANI/rGO shows potential for electrochemical detection of dimethoate affected by the number of bilayers and reduction temperature. The response to acetone vapor is linear from 1 to 60 ppm and detectable at 1 ppm. The sensors do not respond to methanol and some other volatile organic compounds (VOCs) at the same concentration. Food monitoring with total VOCs detection was successfully demonstrated. PANI/rGO sensors feature versatile sensing capabilities, making them feasible due to their rapid production and low cost.

Near-infrared-excitable acetylcholinesterase-activated fluorescent probe for sensitive and anti-interference detection of pesticides in colored food

The development of a common and anti-interference acetylcholinesterase (AChE) inhibition assay for plant-originated food samples has been of great challenge because of the prevalent and strong signal interferences from natural pigments. Plant pigments normally exhibit non-negligible absorbance in the UV-visible region. As a result, the signals of a typical near-infrared (NIR) fluorescent probe could be disturbed through primary inner filter effect if it is excited by UV-visible light during plant sample analysis. In this work, an NIR-excitable AChE-activated fluorescent probe was biomimetically designed and synthesized. And the NIR-excitation strategy was utilized for the anti-interference detection of organophosphate and carbamate pesticides in colored samples with this probe. Sensitive and rapid response to AChE and pesticides was achieved due to the high affinity of the biomimetic recognition unit in the probe. The limits of detection for four representative pesticides including dichlorvos, carbofuran, chlorpyrifos and methamidophos reached 0.0186 μg/L, 2.20 μg/L, 12.3 μg/L and 13.6 μg/L, respectively. Most importantly, fluorescent response to pesticide contents could be accurately measured in the coexistence of different plant pigments by this probe, and the measured results showed completely irrelevance to the plant pigments and their colors. Taking advantage of such probe, the new developed AChE inhibition assay showed good sensitivity and anti-interference ability in the detection of organophosphate and carbamate pesticides in real samples.

Carbon Materials for Organophosphate Pesticide Sensing

Organophosphates are mainly used as pesticides to protect crops from pests. Because organophosphate pesticides’ use has expanded dramatically worldwide, accurate monitoring of their concentrations in the environment and food has become of utmost importance. Once considered acutely toxic due to acetylcholinesterase inhibition, nowadays organophosphates are classified as extremely dangerous compounds, with a broad spectrum of toxicity types, by the World Health Organization. Having in mind their extensive use and diverse harmful effects, it is necessary to develop easy, rapid, and highly sensitive methods for organophosphate detection. Regardless of numerous conventional techniques for organophosphate detection, the construction of portable sensors is required to make routine analysis possible. Extensive literature on the different sensors for organophosphate detection is available. Many of them rely on the use of various carbon materials. There are many classes of carbon materials used in sensing element construction, as well as supporting materials. This review focuses on electrochemical and optical sensors based on carbon materials. Special attention is paid to the selectivity, sensitivity, stability, and reusability of reviewed sensors.

Graphene Based FET Biosensor for Organic-Phosphorous Sample Detection and the Enzymatic Analysis

Our paper presents a flexible enzymatic acetylcholinesterase graphene based FET biosensor of the target organic phosphorous. The sensor’s purpose is to detect pesticide residues in the field of food safety. In our sensor design, the material is graphene with its functionalization, and graphene based FET structure will be discussed in one section of this paper. The mechanism of this graphene sensor is the enzymatic linked reaction on a sensor surface. The enzyme is fixed on the sensor surface by the linker 3-mercapto propionic acid. Measurement experiments using the biosensor were performed for detecting the concentration of isocarbophos (an organophosphate). The enzymatic biosensor has successfully detected 100 μg/mL isocarbophos from the water sample, presenting a significant detection limit index for organophosphate detection.

Ultra-Sensitive Impedimetric Immunosensor Using Copper Oxide Quantum Dots Grafted on the Gold Microelectrode for the Detection of Parathion.

The extensive use of organophosphates (OPs) pollutes the environment, leading to serious health hazards for human beings. The current need is to fabricate a sensing platform that will be sensitive and selective towards the detection of OPs at trace levels in the nM to fM range. With this discussed in the present report, an ultra-sensitive immunosensing platform is developed using digestive-ripened copper oxide quantum dots grafted on a gold microelectrode (Au-µE) for the impedimetric detection of parathion (PT). The copper oxide quantum dots utilized in this study were of ultra-small size with a radius of approximately 2 to 3 nm and were monodispersed with readily available functional groups for the potential immobilization of antibody parathion (Anti-PT). The miniaturization is achieved by the utilization of Au-µE and the microfluidic platform utilized has the sample holding capacity of about 2 to 10 µL. The developed immunosensor provided a wide linear range of detection from 1 µM to 1 fM. The lower Limit of Detection (LoD) for the developed sensing platform was calculated to be 0.69 fM, with the sensitivity calculated to be 0.14 kΩ/nM/mm2. The stability of the sensor was found to be ~40 days with good selectivity. The developed sensor has the potential to integrate with a portable device for field applications.

Portable Rapid Paper-Based Device for Analysis of Carbamates and Organophosphates in Water Samples

Traditionally, the analysis of contaminants in water samples is performed using sophisticated techniques, namely HPLC, GC, and MS, requiring qualified personnel and laboratory infrastructure. Such methods are not feasible for the detection of contaminants in the field. In contrast, paper-based portable devices have been demonstrated as versatile, sustainable, and cheap solutions for such purposes. Paper consists of a pressed sheet of entangled hydrophilic cellulose fibres with excellent porosity. Such features enable the capillarity motion of liquids and the immobilization of active substances on the surface.Pesticides are critical pollutants in regions where agricultural activity is intense and represent a serious health risk for rural workers and their communities. These chemicals have been applied in enormous quantities to increase crop production in many countries. Carbamates (CBs) and organophosphates (OPs) are employed as active ingredients in industrial formulations of insecticides. They are considered highly toxic due to their inhibition action in the cholinergic transmission found in the nervous system of living organisms.This work aims to present a low-cost and simple operational paper-based testing device for the fast detection of CBs and OPs in water samples based on Ellman’s method of acetylcholinesterase (AChE) inhibition. We have named the proposed device “dip-and-fold” due to its how-to-use procedure: first, the device’s bottom edge is dipped in the water sample. The liquid moves up by capillarity towards the detection zone, in which the analytes find the AChE previously immobilized on the paper. The top edge of the paper is covered with a thin parafilm layer to avoid leaking.After a 10-minute incubation, the AChE is inhibited in the presence of CBs and/or OPs. Then, the device is folded to release both enzymatic substrate acetylthiocholine iodide (ACThI) and indicator 5,5′-Dithiobis (2-nitrobenzoic acid) (DTNB) from a secondary paper to the detection zone for the colorimetric reaction. The detection zone area remains white in the presence of CBs and/or OPs (inhibited AChE); otherwise, it becomes yellow in the absence of these pesticides (active AChE).It is worthy to emphasize that the dip-and-fold has all required ingredients immobilized onto the paper substrates prior to tests, which excludes the necessity of extra reagents and materials. Besides, the sample can be transferred to the device by capillarity motion when dipping it directly into the contaminated water, eliminating any risk of having contact with the pesticides. Experiment The dip-and-fold device was fabricated using two analytical papers and a backing card as a foldable scaffold. Blotting paper (Whatman GB003) was used as the main device’s component for the sample loading by capillarity as well as for the immobilization of 3 µL AChE (100 U/mL), using chitosan 1% (w/v, in acetic acid 2%), as a crosslinker. The secondary component was the filter paper (Whatman grade 4) in which the 3µL of the substrate ACThI (25mM) and 3 µL of DTNB (10mM) were impregnated on the surface. The detection tests were carried out using standard solutions of carbofuran, propoxur (both carbamates) and chlorpyriphos (an organophosphate) at concentrations between 0.1 and 0.0001 mM. Control samples of DI water were also tested. A minimum volume of methanol was required to dissolve the pesticides in water. Yellow-coloured results of the tests were evaluated by taking digital photos of the devices using a smartphone. The RGB channels of images were analyzed using ImageJ software. Results and Conclusion The result interpretation was performed by comparing the plotted curves of the blue channel (B) values obtained from the images of each tested device for the different analytes and their respective concentrations. The evaluation of the plotted curves confirmed that the yellow colour's intensity is inversely proportional to the concentration of the analytes in the sample, which means, the more intense the yellow, the lower the concentration of pesticides in the sample. The concentrations applied in this study meet the parameters proposed by the Ontario Drinking Water Quality Standards (ODWQS) and may be compared to other paper-based devices described in the literature.Both propoxur and carbofuran presented consistent results that were observed by a steady decrease of the B values related to their concentration. In contrast, the chlorpyrifos presented a non-linear curve, which can be attributed to the higher amount of methanol used as a co-solvent to dissolve it in water due to its extremely poor solubility.The dip-and-fold device presented an exclusive, eco-friendly, and economical testing platform for pesticide detection in water, which offers an attractive solution for water assessment in vulnerable areas exposed to these toxic chemicals. Figure 1

Monitoring of pesticide amount in water and drinkable food by a fluorescence-based biosensor.

The identification of pollutants is crucial to protect water resources and ensure food safety. The available analytical methodologies allow reliable detection of organic pollutants such as pesticides; however, there is the need for faster, direct and continuous methodologies for real‐time monitoring of pesticides. Fluorescent‐based biosensors have been recently proposed as a valid alternative due to their advantage of being easy, cheap and specific. In this context, the aim of the present EU‐FORA fellowship programme was to develop and apply a fluorescence‐based biosensing device for the detection of organophosphate (OP) pesticides in water samples and drinkable food. The study was addressed using a mutant of the thermostable esterase‐2 from Alicyclobacillus acidocaldarius (EST2‐S35C) as a bioreceptor for OP pesticides. The use of EST2 involves some significant advantages including specificity and affinity towards OPs, and high stability over time in a different range of temperatures and pH. The protein was labelled to the fluorescent probe IAEDANS and fluorescence measurements of quenching in solution and in immobilised form were performed. The results showed good stability and sensitivity, reaching low limits of detection and quantification and a constant signal intensity over time. The addition of paraoxon quenched the fluorescence of the complex, reaching a plateau at 100 pmol paraoxon. The decrease of enzymatic activity of EST2‐S35C‐IAEDANS in the presence of paraoxon correlated the inhibition of the labelled enzyme with the decrease in fluorescence. The results from the application of the biosensor with real samples showed a decrease in fluorescence in surface water samples, contaminated by OPs. The use of the developed fluorescence‐based biosensor demonstrated its applicability for real samples monitoring and could ensure the production of large amounts of data in a short period of time which can be used to address environmental and food safety risk assessment.