Rapid method based on immunoassay for determination of paraquat residues in wheat, barley and potato

Utilizing symmetrical tetramethyl cucurbit[6]uril-based supramolecular fluorescence probe for detection of paraquat in water

A supramolecular fluorescence probe has been developed using a symmetrical tetramethyl cucurbit[6]uril (TMeQ[6]) and a styryl derivative (SPy) with a host-guest ratio of 2:1. The introduction of paraquat (PQ) competes with SPy for the TMeQ[6] cavity, resulting in fluorescent quenching. The addition of 17 common herbicides and ions had negligible effects on the fluorescence quenching, indicating that the 2TMeQ[6]/SPy complex exhibits excellent selectivity in detecting PQ. The detection limit was found to be 4.62 × 10-7 M. More importantly, the probe was engineered to detect paraquat in river water by examining post-treatment samples and noting alterations in fluorescence color. The red to blue (R/B) intensity ratio is subsequently calculated to ascertain the PQ concentration. Experimental trials conducted on river water samples yielded recovery rates between 98.21 % and 108 %, with a relative standard deviation of less than 5 %. By pairing this with a smartphone-based colorimetric analysis application, we can facilitate portable PQ detection, enabling efficient and convenient monitoring across various locations.

Determination of procymidone residues in rapeseed oil based on olfactory visualization technology

A new means about olfactory visualization technique for the quantitative analysis of procymidone residues in rapeseed oil has been proposed. First, an olfactory visualization system was set up to collect volatile odor information from rapeseed oil samples containing different concentrations of procymidone residues. Then, we utilized four intelligent optimization algorithms, namely particle swarm optimization (PSO), genetic algorithm (GA), ant colony optimization (ACO) and simulated annealing (SA), to optimize the characteristics of the sensors. Finally, support vector machine regression (SVR) models employing optimized features were constructed for the quantitative detection of procymidone residues in rapeseed oil. The study demonstrated that the SA-SVR model demonstrated superior prediction results, achieving a high determination coefficient of prediction (R P 2 ) at 0.9894. As indicated by the results, it is possible to successfully conduct non-destructive detection of procymidone residues in edible oil by the olfactory visualization technology.

Detecting different pesticide residues on Hami melon surface using hyperspectral imaging combined with 1D-CNN and information fusion

Efficient, rapid, and non-destructive detection of pesticide residues in fruits and vegetables is essential for food safety. The visible/near infrared (VNIR) and short-wave infrared (SWIR) hyperspectral imaging (HSI) systems were used to detect different types of pesticide residues on the surface of Hami melon. Taking four pesticides commonly used in Hami melon as the object, the effectiveness of single-band spectral range and information fusion in the classification of different pesticides was compared. The results showed that the classification effect of pesticide residues was better by using the spectral range after information fusion. Then, a custom multi-branch one-dimensional convolutional neural network (1D-CNN) model with the attention mechanism was proposed and compared with the traditional machine learning classification model K-nearest neighbor (KNN) algorithm and random forest (RF). The traditional machine learning classification model accuracy of both models was over 80.00%. However, the classification results using the proposed 1D-CNN were more satisfactory. After the full spectrum data was fused, it was input into the 1D-CNN model, and its accuracy, precision, recall, and F1-score value were 94.00%, 94.06%, 94.00%, and 0.9396, respectively. This study showed that both VNIR and SWIR hyperspectral imaging combined with a classification model could non-destructively detect different pesticide residues on the surface of Hami melon. The classification result using the SWIR spectrum was better than that using the VNIR spectrum, and the classification result using the information fusion spectrum was better than that using SWIR. This study can provide a valuable reference for the non-destructive detection of pesticide residues on the surface of other large, thick-skinned fruits.

Non-Destructive Detection of Different Pesticide Residues on the Surface of Hami Melon Classification Based on tHBA-ELM Algorithm and SWIR Hyperspectral Imaging

In the field of safety detection of fruits and vegetables, how to conduct non-destructive detection of pesticide residues is still a pressing problem to be solved. In response to the high cost and destructive nature of existing chemical detection methods, this study explored the potential of identifying different pesticide residues on Hami melon by short-wave infrared (SWIR) (spectral range of 1000-2500 nm) hyperspectral imaging (HSI) technology combined with machine learning. Firstly, the classification effects of classical classification models, namely extreme learning machine (ELM), support vector machine (SVM), and partial least squares discriminant analysis (PLS-DA) on pesticide residues on Hami melon were compared, ELM was selected as the benchmark model for subsequent optimization. Then, the effects of different preprocessing treatments on ELM were compared and analyzed to determine the most suitable spectral preprocessing treatment. The ELM model optimized by Honey Badger Algorithm (HBA) with adaptive t-distribution mutation strategy (tHBA-ELM) was proposed to improve the detection accuracy for the detection of pesticide residues on Hami melon. The primitive HBA algorithm was optimized by using adaptive t-distribution, which improved the structure of the population and increased the convergence speed. Compared the classification results of tHBA-ELM with HBA-ELM and ELM model optimized by genetic algorithm (GA-ELM), the tHBA-ELM model can accurately identify whether there were pesticide residues and different types of pesticides. The accuracy, precision, sensitivity, and F1-score of the test set was 93.50%, 93.73%, 93.50%, and 0.9355, respectively. Metaheuristic optimization algorithms can improve the classification performance of classical machine learning classification models. Among all the models, the performance of tHBA-ELM was satisfactory. The results indicated that SWIR-HSI coupled with tHBA-ELM can be used for the non-destructive detection of pesticide residues on Hami melon, which provided the theoretical basis and technical reference for the detection of pesticide residues in other fruits and vegetables.

Electrochemical sensor for ultrasensitive detection of paraquat based on metal-organic frameworks and para-sulfonatocalix[4]arene-AuNPs composite

The widespread occurrence of pesticides in surface water, groundwater, soil, and food has received increasing attention towards environmental safety. Paraquat (PQ) is world widely used as a rapid sterilant herbicide and is highly toxic to humans. A simple, rapid, sensitive, and on-site detection method for the water environment to detection of PQ is urgently required. Here, we prepared a zeolite imidazole skeleton-8 (ZIF-8) and para-sulfonylcalix[4]arene (pSC₄) coated gold nanoparticles composite (pSC₄-AuNPs@ZIF-8) by one-step method. An electrochemical biosensor assay for PQ was established based on pSC₄-AuNPs@ZIF-8 modified glassy carbon electrode through host-guest recognition of PQ and pSC₄. Under the optimal conditions, recoveries of targets determination results were 92.7%-103% (n = 3), respectively. The quantity PQ detection limit was found to be 0.49 pM. Therefore, the signal amplification strategy based on pSC₄-AuNPs@ZIF-8 has potential value in detecting trace pollutants in the water environment.

Regulation of Paraquat for wheat crop contamination

Paraquat is a highly toxic and persistent pesticide in soil but is still used for wheat crops in many countries. Paraquat can pose potential health hazards if it is translocated from soil into wheat grains, but no study is available for its possible translocation causing wheat grain contamination. The present study aimed at finding out Paraquat residue in wheat grains under field conditions for two crop seasons to explore the sustainability of this pesticide. The experiments were conducted scientifically under field conditions at agricultural fields Pusa, Delhi, India. The soil texture was classified as sandy loam. Paraquat dichloride 24% SL (herbicide) was applied on five fields except for control field. Paraquat in wheat grains was analyzed using HPLC equipped with a photodiode array (PDA) detector. The method of analysis was validated for the pesticide residue recovery. The results showed that there was an alarming concentration of Paraquat in wheat grains ranging between 21.6 and 49.02 mg kg^-1 against maximum residue level of 0.1 mg kg^-1. Paraquat was also found in control crop (3.1 mg kg^-1) due to background residue in soil even when no Paraquat was applied. Furthermore, wheat flour samples from market also gave alarming Paraquat residue (20.39, 25.88, and 27.68 mg kg^-1). Paraquat residue was primarily dependent on % clay in field soils. More the % clay lesser was Paraquat residue in wheat grain. Thus, Paraquat was translocated from soil into wheat grains and resulted in worrying concentration of Paraquat residue in wheat grains. Consequently, use of Paraquat for wheat crops needs to be regulated as it contaminated the soil and resulted in the wheat grain contamination posing severe health hazards for humans.

Glyphosate vs. Glyphosate-Based Herbicides Exposure: A Review on Their Toxicity

Glyphosate-based herbicide has been the first choice for weed management worldwide since the 1970s, mainly due to its efficacy and reported low toxicity, which contributed to its high acceptance. Many of the recent studies focus solely on the persistence of pesticides in soils, air, water or food products, or even on the degree of exposure of animals, since their potential hazards to human health have raised concerns. Given the unaware exposure of the general population to pesticides, and the absence of a significant number of studies on occupational hazards, new glyphosate-induced toxicity data obtained for both residual and acute doses should be analyzed and systematized. Additionally, recent studies also highlight the persistence and toxicity of both glyphosate metabolites and surfactants present in herbicide formulations. To renew or ban the use of glyphosate, recently published studies must be taken into account, aiming to define new levels of safety for exposure to herbicide, its metabolites, and the toxic excipients of its formulations. This review aims to provide an overview of recent publications (2010–present) on in vitro and in vivo studies aimed at verifying the animal toxicity induced by glyphosate, its metabolite aminomethylphosphonic acid (AMPA) and glyphosate-based formulations, evaluated in various experimental models. Apart from glyphosate-induced toxicity, recent data concerning the role of surfactants in the toxicity of glyphosate-based formulations are discussed.

Ready-to-use paraquat sensor using a graphene-screen printed electrode modified with a molecularly imprinted polymer coating on a platinum core

We propose the fabrication of a novel ready-to-use electrochemical sensor based on a screen-printed graphene paste electrode (SPGrE) modified with platinum nanoparticles and coated with a molecularly imprinted polymer (PtNPs@MIP) for sensitive and cost-effective detection of paraquat (PQ) herbicide. Successive coating of the PtNPs surface with SiO₂ and vinyl end-groups formed the PtNPs@MIP. Next, we terminated the vinyl groups with a molecularly imprinted polymer (MIP) shell. MIP was attached to the PtNPs cores using PQ as the template, methacrylic acid (MAA) as the monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, and 2,2'-azobisisobutyronitrile (AIBN) as the initiator. Coating the SPGrE surface with PtNPs@MIP furnished the PQ sensor. We studied the electrochemical mechanism of PQ on the MIP sensor using cyclic voltammetry (CV) experiments. The PQ oxidation current signal appears at -1.08 V and -0.71 V vs. Ag/AgCl using 0.1 M potassium sulfate solution. Quantitative analysis was performed by anodic stripping voltammetry (ASV) using a deposition potential of -1.4 V for 60 s and linear sweep voltammetric stripping. The MIP sensor provides linearity from 0.05 to 1000 μM (r² = 0.999), with a lower detection limit of 0.02 μM (at -0.71 V). The compact imprinted sensor gave a highly sensitive and selective signal toward PQ. The ready-to-use MIP sensor can provide an alternative approach to the determination of paraquat residue on vegetables and fruits for food safety applications.

Monitoring of Paraquat in soya products intended for animal feed

Even though paraquat is considered to be one of the most toxic herbicides, it is one of the most used ones. Paraquat-based preparations are heavily used across many important agricultural countries and for a lot of types of crops such as soya. As soya is used in large quantities in the feed production, paraquat residues in soya products are a potential threat to livestock. The aim of this study was to investigate whether soya products intended for animal feed contain residues of paraquat. Therefore, an optimized Quick Polar Pesticides (QuPPe) Method was developed. In total, 174 samples were analyzed via LC-MS/MS using zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC). The results showed that paraquat was detected in 66 % of the samples above 0.008 mg/kg. Residues were mainly present in soya bean meals that were imported from Brazil or the USA and cultivated using genetically modified soya. Around 5 % of the samples were not compliant with the European regulation on maximum residue levels of pesticides in or on food and feed. The results of this study support the view that paraquat residues play a significant role in soya products intended for animal feed and, thus, need to be controlled on a regular basis. However, for enforcement actions reliable processing factors for paraquat in soya products or maximum residue levels for processed soya products are urgently required.

Aptasensor for paraquat detection by gold nanoparticle colorimetric method

This study aimed to develop an aptasensor for paraquat detection by gold nanoparticles. The specific aptamer for paraquat was selected by using the SELEX process via capillary electrophoresis. Sixty-three aptamer candidates were amplified by asymmetric PCR and screened for paraquat binding using gold nanoparticles (AuNPs). Aggregation of AuNPs was specifically induced by desorption of paraquat binding aptamers from the surface of AuNPs as a result of aptamer-target interaction leading to the color change from red to purple. Aptamer 77F with the following sequence: 5'-AGGCTTACACCTGAAAAGCGGCTTAATTTACACTACTGTAT-3' was selected as a highly specific aptamer for paraquat. The detection limit of paraquat was 0.267 µg/mL by colorimetry and 1.573 µg/mL by the quartz crystal microbalance (QCM) technique. This aptamer showed specificity for paraquat by colorimetry. Dimethyl phophite, diethyl phophite and O,O diethyl thiophosphate potassium salt did not react by colorimetry but, exhibited a weak nonspecific reaction by QCM. This is first time that an aptasensor was used for detection of paraquat based on QCM. However, the aptasensor based on the colorimetric method simply uses a generation of a signal that can be detected by the naked eye. This technique is rapid, low cost easy to use and suitable for on-site detection of herbicide residue.

Supramolecular Solvent-Based Liquid Phase Microextraction Combined with Ion-Pairing Reversed-Phase HPLC for the Determination of Quats in Vegetable Samples

In this study, we used anion supramolecular solvent (SUPRAS) prepared from a mixture of an anionic surfactant, sodium dodecyl sulfate (SDS), and a cationic surfactant, tetrabutylammonium bromide (TBABr), as the extraction solvent in liquid phase microextraction (LPME) of paraquat (PQ) and diquat (DQ). The enriched PQ and DQ in the SUPRAS phase were simultaneously analyzed by ion-pairing reversed-phase high performance liquid chromatography. PQ and DQ were successfully extracted by LPME via electrostatic interaction between the positive charge of the quats and the negative charge of SUPRAS. PQ, DQ, and ethyl viologen (the internal standard) were separated within 15 min on a C18 column, with the mobile phase containing 1-dodecanesulfonic acid and triethylamine, via UV detection. The optimized conditions for the extraction of 10 mL aqueous solution are 50 μL of SUPRAS prepared from a mixture of SDS and TBABr at a mole ratio of 1:0.5, vortexed for 10 s at 1800 rpm, and centrifugation for 1 min at 3500 rpm. The obtained enrichment factors were 22 and 26 with limits of detection of 1.5 and 2.8 µg L^-1 for DQ and PQ, respectively. The precision was good with relative standard deviations less than 3.86%. The proposed method was successfully applied for the determination of PQ and DQ in vegetable samples and recoveries were found in the range of 75.0% to 106.7%.

Preparing monoclonal antibodies and developing immunochromatographic strips for paraquat determination in water

Paraquat (PQ) poisoning is a serious threat to human health that leads to pulmonary toxicity, neurotoxicity, and inflammation. Protecting humans from PQ exposure requires the development of rapid analytical methods for on-site detection. Here, two monoclonal antibodies against PQ were generated and an immunochromatographic assay (ICA) was exploited to determine PQ concentrations in water samples. The results showed that the monoclonal antibody 1D6 exhibited higher affinity and sensitivity, with an affinity constant of 5.4 × 10⁸ mol/L and a limit of detection as low as 0.02 ng/mL. Without sample pretreatment, the developed ICA method provided visible limits of detection ranging from 0.25 to 1 ng/mL, and cut-off limits ranging from 1 to 5 ng/mL, where average recoveries were between 83.15% ± 1.9% and 94.49% ± 2.45% with a coefficient of variation ranging from 1.40% to 7.37%. Importantly, these observations were consistent with liquid chromatography tandem mass spectrometry. These data and results suggested that the ICA method was a reliable, portable, and high-throughput method for determining PQ residues in water samples.

Enzyme-linked immunosorbent assays for therapeutic drug monitoring coumarin oral anticoagulants in plasma

The development of high-throughput immunochemical assays to assist on precision medicine for patients treated with coumarin oral anticoagulants (OA) is reported. The assays are able to quantitate Warfarin (W) and/or Acenocoumarol (ACL) directly in plasma samples without any previous sample pretreatment. The detectabilities (W, 3.52 ± 2.25 nM and ACL, 1.56 ± 0.64 nM) and the working ranges achieved (W, 1.19 ± 0.73 to 12.05 ± 2.99 nM and ACL 0.63 ± 0.20 to 10.19 ± 6.69 nM) are within the therapeutic levels usually found in patients treated with these drugs. The assays are specific with only cross-recognition of 4'-NH₂-ACL on the ACL ELISA, which is one of the main metabolites of this drug. Moreover, accuracy studies performed with blind spiked samples show very good correlation between the spiked and the measured concentrations. Finally, a small clinical pilot study has been performed analyzing 96 plasma samples from treated and untreated patients, showing that the assay is able to quantitate ACL. The results obtained allow envisaging the possibility to use these assays for pharmacokinetic studies, dosage assessment or therapeutic drug monitoring.

Simultaneous determination of paraquat and atrazine in water samples with a white light reflectance spectroscopy biosensor

An optical immunosensor based on White Light Reflectance Spectroscopy for the simultaneous determination of the herbicides atrazine and paraquat in drinking water samples is demonstrated. The biosensor allows for the label-free real-time monitoring of biomolecular interactions taking place onto a SiO₂/Si chip by transforming the shift in the reflected interference spectrum due to reaction to effective biomolecular layer thickness. Dual-analyte determination is accomplished by functionalizing spatially distinct areas of the chip with protein conjugates of the two herbicides and scanning the surface with an optical reflection probe. A competitive immunoassay format was adopted, followed by reaction with secondary antibodies for signal enhancement. The sensor was highly sensitive with detection limits of 40 and 50 pg/mL for paraquat and atrazine, respectively, and the assay duration was 12 min. Recovery values ranging from 90.0 to 110% were determined for the two pesticides in spiked bottled and tap water samples, demonstrating the sensor accuracy. In addition, the sensor could be regenerated and re-used at least 20 times without significant effect on the assay characteristics. Its excellent analytical performance and short analysis time combined with the small sensor size should be helpful for fast on-site determinations of these analytes.

Advancements of molecularly imprinted polymers in the food safety field

Molecularly imprinted technology (MIT) has been widely employed to produce stable, robust and cheap molecularly imprinted polymer (MIP) materials that possess selective binding sites for recognition of target analytes in food, such as pesticides, veterinary drugs, mycotoxins, illegal drugs and so on. Because of high selectivity and specificity, MIPs have drawn great attention in the food safety field. In this review, the recent developments of MIPs in various applications for food safety, including sample preparation, chromatographic separation, sensing, immunoassay etc., have been summarized. We particularly discuss the advancements and limitations in these applications, as well as attempts carried out for their improvement.

Supramolecular fluorescent sensor array for simultaneous qualitative and quantitative analysis of quaternary ammonium herbicides

A supramolecular fluorescent sensor array was firstly used to simultaneously qualitatively and quantitatively analyze quaternary ammonium herbicides.

Analysis of sulfonamides, tilmicosin and avermectins residues in typical animal matrices with multi-plug filtration cleanup by liquid chromatography-tandem mass spectrometry detection

The frequent use of various veterinary drugs could lead to residue bioaccumulation in animal tissues, which could cause dietary risks to human health. In order to quickly analyze the residues, a liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for detecting Sulfonamides, Tilmicosin and Avermectins (AVMs) residues in animal samples. For sample preparation, modified QuEChERS (quick, easy, cheap, effective, rugged and safe) and ultrasound-assisted extraction (UAE) methods were used. For sample cleanup, n-Hexane delipidation and multi-plug filtration cleanup (m-PFC) method based on primary-secondary amine (PSA) and octadecyl-silica (C18) were used, followed by LC-MS/MS analysis. It was validated on 7 animal matrices (bovine, caprine, swine meat and their kidneys, milk) at two fortified concentration levels of 5 and 100μg/kg. The recoveries ranged from 82 to 107% for all analytes with relative standard deviations (RSDs) less than 15%. Matrix-matched calibrations were performed with coefficients of determination above 0.998 for all analytes within concentration levels of 5-500μg/kg. The developed method was successfully used to analysis veterinary drugs of real animal samples from local markets.

Facile Synthesis of Glutathione-capped CdS Quantum Dots as a Fluorescence Sensor for Rapid Detection and Quantification of Paraquat

This paper describes a convenient and rapid fluorescence sensor for determination of paraquat (PA) based on glutathione-capped CdS quantum dots (QDs). The methodology enabled the use of a simple synthesis procedure for water solubilization of CdS QDs via a fast route using glutathione as a capping agent within 15 min. The resulting water-soluble QDs exhibit a strong fluorescence emission at 536 nm with high and reproducible photostability. PA is an important class of electron acceptors for QDs. Thus, the fluorescence intensity of the glutathione-capped CdS QDs probe could be dramatically quenched by PA due to the electron transfer mechanism. The fluorescence intensity of the CdS QDs system was proportional to PA concentration in the range of 0.025 to 1.5 μg mL(-1), with a detection limit of 0.01 μg mL(-1). The time of analysis sample, including preparation of QDs and fluorescent measurement for PA, was only 20 min. Most of the potentially coexisting substances did not interfere with the PA-induced quenching effect except diquat. Furthermore, the analytical applicability of the proposed method was demonstrated by analyzing PA in water, rice and cabbage samples, and the recoveries were between 86 and 105% which satisfied the requirement of detection for PA. These results showed that the proposed method was simple in design and fast in operation, and could be used as a sensitive tool for detecting PA in environmental and agricultural samples.

Development of an Immunoassay for the Detection of the Phenylpyrazole Insecticide Fipronil

Phenylpyrazole insecticides such as fipronil have been used as replacements for organophosphates. The wide application of fipronil raises concern about environmental contamination and risk for fish, birds, and other nontargeted beings as well as human health. A sensitive, competitive indirect heterologous enzyme-linked immunosorbent assay (ELISA) was developed. Antibodies with different specificities to fipronil and its metabolites were produced. Two ELISAs having IC50 values of 0.58 ± 0.06 and 2.6 ± 0.4 ng/mL were developed. Design of different haptens and coating antigens resulted in two assays with distinct cross-reactivity patterns for structurally related compounds: 96, 38, and 101% versus 39, 1.4, and 25% for fipronil-sulfide, fipronil-detrifluoromethylsulfonyl, and fipronil-desulfinyl, respectively. Performance of the immunoassays was demonstrated by a recovery study from spiked water and human serum and urine matrices, giving recovery values in the range of 85-111% for different concentrations. The assays demonstrated good correlation in fipronil recovery with conventional LC-MS/MS analysis. The generic assay 2265 has the sensitivity to measure fipronil and its analogs in serum at levels relevant for exposure monitoring. The assays were used to analyze human urine samples obtained from exposure studies and serum samples from rats treated with a fipronil-containing diet.

A sensitive monoclonal antibody-based enzyme-linked immunosorbent assay for the detection of bifenthrin in a chemical soil barrier

A sensitive monoclonal antibody-based enzyme monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA) was developed to detect bifenthrin in a chemical soil barrier for termite control. LBc ((2-methyl[1,1-biphenyl]-3-methoxy) carbonyl propionic acid) was conjugated to bovine serum albumin (BSA) for producing monoclonal antibody. After optimization, the IC50 and limit of detection (LOD, IC10) were 0.05 mg L(-1) and 0.004 mg L(-1), respectively. The sensitivity was improved 40-fold compared to polyclonal antibody-based ELISA reported earlier. No cross-reactivity was measured for the other analogues such as cyhalothrin, cyhalothric acid, cypermethrin, deltamethrin, fenpropathrin, fenvalerate, ethofenprox and tetramethrin except 2-methyl-3-biphenylmethyanol. Spiked recoveries were between 83.5% and 104.7% for the detection of bifenthrin in loess, red soil and black soil. All the relative standard deviations (RSDs) were less than or equal to 15.0%. Moreover, the ELISA for authentic samples showed reliability and high correlation with gas chromatography. The developed ELISA is an alternative tool for simple, sensitive and accurate monitoring of bifenthrin in chemical soil barriers.

A host–guest complexation based fluorescent probe for the detection of paraquat and diquat herbicides in aqueous solutions

A new method based on fluorescence quenching of host–guest complexation was proposed for the determination of the two herbicides in river water and cabbages. The method is rapid, direct and simple.