Voltammetric Determination of Neonicotinoid Pesticides at Disposable Screen-Printed Sensors Featuring a Sputtered Bismuth Electrode

Reviewing neonicotinoid detection with electroanalytical methods

Neonicotinoids, as the fastest-growing class of insecticides, currently account for over 25% of the global pesticide market. Their effectiveness in controlling a wide range of pests that pose a threat to croplands, home yards/gardens, and golf course greens cannot be denied. However, the extensive use of neonicotinoids has resulted in significant declines in nontarget organisms such as pollinators, insects, and birds. Furthermore, the potential chronic, sublethal effects of these compounds on human health remain largely unknown. To address these pressing issues, it is crucial to explore and understand the capabilities of electrochemical sensors in detecting neonicotinoid residues. Surprisingly, despite the increasing importance of this topic, no comprehensive review article currently exists in the literature. Therefore, our proposed review aims to bridge this gap by providing a thorough analysis of the use of electrochemical methods for neonicotinoid determination. In this review article, we will delve into various aspects of electrochemical analysis, including the influence of electrode materials, employed techniques, and the different types of electrode mechanisms utilized. By synthesizing and analysing the existing research in this field, our review will offer valuable insights and guidance to researchers, scientists, and policymakers alike.

Development of an electrochemical sensor based on ternary oxide SiO2/Al2O3/SnO2 modified with carbon black for direct determination of clothianidin in environmental and food samples

This study presents the development of an electrochemical sensor, denoted as GCE/CB/SiAlSn, based on the modification of a glassy carbon electrode surface with the ternary oxide SiO2/Al2O3/SnO2 associated with carbon black, for direct determination of the neonicotinoid pesticide clothianidin in different matrices, such as environmental and food samples. Morphological characterization by the scanning electron microscopy technique, electroanalytical analyses using the cyclic voltammetry technique and differential pulse voltammetry are presented which demonstrated that the developed electrochemical platform presents high sensitivity in the electroanalytical clothianidin determination. The linear range studied was from 2.99 × 10-7 to 6.04 × 10-5 mol L-1, with an LOD of 2.47 nmol L-1. This high sensitivity was explained using the synergistic relationship between carbon black and ternary oxide that maximized the electroactive surface area of the GCE/CB/SiAlSn sensor. Interferent studies were performed that showed high selectivity of the sensor to the pesticide in the presence of Ca2+, K+, Na+, and Mg2+ and carbendazim, glyphosate, imidacloprid and thiamethoxam pesticides. The sensor was applied to real samples of tap water and apple juice obtaining recoveries from 91.0% to 103.0%.

Silver nanoparticle-modified electrodes for the electrochemical detection of neonicotinoid pesticide: clothianidin

For the first time, stable silver nanoparticles with a diameter less than 20 nm were prepared using SDS as a reducing and stabilizing agent and characterized, and then used to construct modified electrodes. The developed electrodes are more catalytically active towards the reduction of clothianidin. Clothianidin undergoes reduction at -300 mV vs. Ag/AgCl on the silver nanoparticle-modified electrode, whereas no reduction peak was observed on a bare glassy carbon electrode (GCE). The detection limit was found to be 2.4 nM. The reduction potential and detection limits reported in this work are lower than ever reported in the literature. The analytical validity of clothianidin was tested using tomatoes. Validation of electrochemical results has been achieved by comparing them to HPLC results. There is a good agreement between the results and those obtained by HPLC. The proposed sensor opens up new possibilities for the sensing of clothianidin in environmental samples.

Electrochemical Sensing of Neonicotinoids Using Laser-Induced Graphene

Neonicotinoids are the fastest-growing insecticide accounting for over 25% of the global pesticide market and are capable of controlling a range of pests that damage croplands, home yards/gardens, and golf course greens. However, widespread use has led to nontarget organism decline in pollinators, insects, and birds, while chronic, sublethal effects on humans are still largely unknown. Therefore, there is a need to understand how prevalent neonicotinoids are in the environment as there are currently no commercially available field-deployable sensors capable of measuring neonicotinoid concentrations in surface waters. Herein, we report the first example of a laser-induced graphene (LIG) platform that utilizes electrochemical sensing for neonicotinoid detection. These graphene-based sensors are created through a scalable direct-write laser fabrication process that converts polyimide into LIG, which eliminates the need for chemical synthesis of graphene, ink formulation, masks, stencils, pattern rolls, and postprint annealing commonly associated with other printed graphene sensors. The LIG electrodes were capable of monitoring four major neonicotinoids (CLO, IMD, TMX, and DNT) with low detection limits (CLO, 823 nM; IMD, 384 nM; TMX, 338 nM; and DNT, 682 nM) and a rapid response time (∼10 s) using square-wave voltammetry without chemical/biological functionalization. Interference testing exhibited negligible responses from widely used pesticides including the broad-leaf insecticides parathion, paraoxon, and fipronil, as well as systemic herbicides glyphosate (roundup), atrazine, dicamba, and 2,4-dichlorophenoxyacetic acid. These scalable, graphene-based sensors have the potential for wide-scale mapping of neonicotinoids in watersheds and potential use in numerous electrochemical sensor devices.

A Review of Nanocomposite-Modified Electrochemical Sensors for Water Quality Monitoring

Electrochemical sensors play a significant role in detecting chemical ions, molecules, and pathogens in water and other applications. These sensors are sensitive, portable, fast, inexpensive, and suitable for online and in-situ measurements compared to other methods. They can provide the detection for any compound that can undergo certain transformations within a potential window. It enables applications in multiple ion detection, mainly since these sensors are primarily non-specific. In this paper, we provide a survey of electrochemical sensors for the detection of water contaminants, i.e., pesticides, nitrate, nitrite, phosphorus, water hardeners, disinfectant, and other emergent contaminants (phenol, estrogen, gallic acid etc.). We focus on the influence of surface modification of the working electrodes by carbon nanomaterials, metallic nanostructures, imprinted polymers and evaluate the corresponding sensing performance. Especially for pesticides, which are challenging and need special care, we highlight biosensors, such as enzymatic sensors, immunobiosensor, aptasensors, and biomimetic sensors. We discuss the sensors' overall performance, especially concerning real-sample performance and the capability for actual field application.

Electrochemical sensor based on multi-walled carbon nanotubes for imidacloprid determination

A simple and robust sensor (fMWCNT-Nafion®0.5%/GCE) for determination of imidacloprid (IMI), a widely used neonicotinoid, was developed using a glassy carbon electrode (GCE) modified with functionalized multi-walled carbon nanotubes (fMWCNT) and Nafion®. The obtained data suggest that IMI reduction is an irreversible process, due to the reduction of the nitro group to hydroxylamine derivatives, with the participation of two protons and four electrons, and a charge transfer coefficient of 0.141. The optimized square-wave voltammetric conditions were: McIlvaine buffer at pH 6.0, 0.5% of Nafion® in the fMWCNT suspension, -0.6 V and 180 s as accumulation potential and time, respectively. A linearity in the range of 2.00 × 10-7 to 1.77 × 10-6 mol L-1 IMI, with the values of limit of detection and limit of quantification were equal to 3.74 × 10-8 mol L-1 and 1.25 × 10-7 mol L-1, respectively. Repeatability and reproducibility displayed relative standard deviations lower than 5%. Recovery tests performed in tap water, melon, and shrimp yielded mean values of 94 ± 6%, 97 ± 10% and 93 ± 10%, respectively. Moreover, several inorganic and organic compounds did not significantly interfere (0.6 to 4.5%) on the IMI signal, proving the selectivity and applicability of the developed sensor for IMI detection in complex samples.

A vibrational spectroscopic and computational study of the structures of protonated imidacloprid and its fragmentation products in the gas phase

Infrared multiple photon dissociation (IRMPD) spectroscopy experiments in the 600-2000 cm^-1 region and computational chemistry studies were combined with the aim of elucidating the structures of protonated imidacloprid (pIMI), and its unimolecular decomposition products. The computed IR spectra for the lowest energy structures for pIMI as well as for protonated desnitrosoimidacloprid, corresponding to the loss of NO radical (pIMI-NO), and protonated imidacloprid urea corresponding to the loss of N₂O (pIMIU) were found to reproduce the experimental IRMPD spectrum quite well. The complex IRMPD spectrum for protonated desnitroimidaclpride (pDIMI), resulting from the loss of NO₂ radical from pIMI, was explained as a contribution from several computed structures, including those involving simple loss of NO₂ radical and some isomerization. However, based on a comparison of the computed IR spectrum for the lowest energy structure of pDIMI and the IRMPD spectrum, it was concluded that the lowest energy structure is a minor contributor to the experimental spectrum. This observation is rationalized as being due to the energy requirement for isomerization to the lowest energy structure, being substantially higher than that for simple loss of NO₂ radical. Experimental mass spectrometry fragmentation results indicated that the loss of N, O₂, H was the result of a loss of NO radical followed by loss of OH radical. A comparison of the experimental IRMPD and computed IR spectra revealed that following NO radical loss, the structure entailing a hydride shift from the methylene bridge to the guanidine moiety followed by OH radical elimination, generated the best match with the experimental IRMPD spectrum. This was consistent with the computed potential energy surfaces showing this structure as having the lowest energy requirement.

Rapid and Sensitive Quantification of the Pesticide Lindane by Polymer Modified Electrochemical Sensor

Lindane is documented by the Environmental Protection Agency (EPA) as one of the most toxic registered pesticides. Conventional detection of lindane in the environment requires manual field sampling and complex, time-consuming analytical sample handling relying on skilled labor. In this study, an electrochemical sensing system based on a modified electrode is reported. The system is capable of detecting lindane in aqueous medium in only 20 s. The surface of a conventional carbon electrode is modified with a film of conductive polymer that enables detection of lindane down to 30 nanomolar. The electrode modification procedure is simple and results in a robust sensor that can withstand intensive use. The sensitivity of the sensor is 7.18 µA/µM and the performance was demonstrated in the determination of lindane in spiked ground water. This suggests that the sensor is potentially capable of providing useful readings for decision makers. The rapid and sensitive quantification of lindane in aqueous medium is one step forward to new opportunities for direct, autonomous control of the pesticide level in the environment.

Electrochemical (Bio)Sensors for Pesticides Detection Using Screen-Printed Electrodes

Pesticides are among the most important contaminants in food, leading to important global health problems. While conventional techniques such as high-performance liquid chromatography (HPLC) and mass spectrometry (MS) have traditionally been utilized for the detection of such food contaminants, they are relatively expensive, time-consuming and labor intensive, limiting their use for point-of-care (POC) applications. Electrochemical (bio)sensors are emerging devices meeting such expectations, since they represent reliable, simple, cheap, portable, selective and easy to use analytical tools that can be used outside the laboratories by non-specialized personnel. Screen-printed electrodes (SPEs) stand out from the variety of transducers used in electrochemical (bio)sensing because of their small size, high integration, low cost and ability to measure in few microliters of sample. In this context, in this review article, we summarize and discuss about the use of SPEs as analytical tools in the development of (bio)sensors for pesticides of interest for food control. Finally, aspects related to the analytical performance of the developed (bio)sensors together with prospects for future improvements are discussed.

Electrochemical determination of bentazone using simple screen-printed carbon electrodes

Bentazone is one of the most problematic pesticides polluting groundwater resources. It is on the list of pesticides that are mandatory to analyze at water work controls. The current pesticide measuring approach includes manual water sampling and time-consuming chromatographical quantification of the bentazone content at centralized laboratories. Here, we report the use of an electrochemical approach for analytical determination of bentazone that takes 10 s. The electrochemical electrodes were manually screen printed, resulting in the low-cost fabrication of the sensors. The current response was linearly proportional to the bentazone concentration with a R² ~ 0.999. We demonstrated a sensitivity of 0.0987 μA/μM and a limit of detection of 0.034 μM, which is below the U.S. Health Advisory level. Furthermore, the sensors have proved to be reusable and stable with a drop of only 2% after 15 times reuse. The sensors have been applied to successfully quantify bentazone spiked in real groundwater and lake water. The sensing method presented here is a step towards on-site application of electrochemical detection of pesticides in water sources.

Enhanced Quenching Effect of Neonicotinoid Pesticides on Time-Resolved Terbium Luminescence in Presence of Surfactants

A luminescence analytical method for the quantification of neonicotinoid pesticides (acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam) in water samples is proposed. The method is based on the quenching effect that these analytes produce on the time-resolved luminescence signal of terbium ions (excitation/emission wavelengths of 256/545 nm/nm). An enhancement on the analytical signal is observed when surfactants are used in the system. The use of a 0.01 mol·L−1 sodium dodecyl sulfate produced approximately a 30% increase in the sensitivity of the method. Under the optimum conditions, the method presented detection limits between 0.03 and 0.23 µg·mL−1. Interference studies were performed for ions commonly present in waters, observing no interferences. In addition, recovery experiments were performed in different waters, well, spring, and swamp, observing recovery yields close to 100%, with relative standard deviations lower than 4% in all cases. No sample treatment except a filtration step was required. Hence, this method may represent an alternative to other existing methods for the quick and simple analysis of these ubiquitous insecticides in environmental waters.

Can the mechanical activation (polishing) of screen-printed electrodes enhance their electroanalytical response?

The mechanical activation (polishing) of screen-printed electrodes (SPEs) is explored and shown to exhibit an improved voltammetric response (in specific cases) when polished with either commonly available alumina slurry or diamond spray. Proof-of-concept is demonstrated for the electrochemical sensing of nitrite where an increase in the voltammetric current is found using both polishing protocols, exhibiting an improved limit of detection (3σ) and a two-fold increase in the electroanalytical sensitivity compared to the respective un-polished counterpart. It is found that mechanical activation/polishing increases the C/O ratio which significantly affects inner-sphere electrochemical probes only (whereas outer-sphere systems remain unaffected). Mechanical activation/polishing has the potential to be a simple pre-treatment technique that can be extended and routinely applied towards other analytes for an observable improvement in the electroanalytical response.

A photochemically induced fluorescence based flow-through optosensor for screening of nitenpyram residues in cruciferous vegetables

One of the most used agrochemicals in agricultural production, nitenpyram (NTP), has been determined by using a flow-through optosensing device based on Photochemically Induced Fluorescence detection. The combination of both methodologies allows, on one hand, a quick on-line photodegradation of NTP and, on the other hand, the preconcentration, quantification and desorption of the fluorescent photoproduct generated when retained on Sephadex QAE-A25 as solid support, which was monitored at 295 and 362 nm for excitation and emission, respectively. The proposed analytical method presents a detection limit of 500 pg mL^-1 by using Multicommutated Flow Injection Analysis. Recovery experiments were carried out in different kinds of cruciferous vegetables at or below the MRL established in Japan, demonstrating that this method combines advantages of simplicity, high sensibility and high selectivity, fulfilling the requirements for its application in quality control. Results obtained in the analysis of real samples were in good agreement with those provided by a reference HPLC method.

Novel potentiometric sensors for the determination of the dinotefuran insecticide residue levels in cucumber and soil samples

Five new potentiometric membrane sensors for the determination of the dinotefuran levels in cucumber and soil samples have been developed. Four of these sensors were based on a newly designed molecularly imprinted polymer (MIP) material consisting of acrylamide or methacrylic acid as a functional monomer in a plasticized PVC (polyvinyl chloride) membrane before and after elution of the template. A fifth sensor, a carboxylated PVC-based sensor plasticized with dioctyl phthalate, was also prepared and tested. Sensor 1 (acrylamide washed) and sensor 3 (methacrylic acid washed) exhibited significantly enhanced responses towards dinotefuran over the concentration range of 10^-7-10^-2molL^-1. The limit of detection (LOD) for both sensors was 0.35µgL^-1. The response was near-Nernstian, with average slopes of 66.3 and 50.8mV/decade for sensors 1 and 3 respectively. Sensors 2 (acrylamide non-washed), 4 (methacrylic acid non-washed) and 5 (carboxylated-PVC) exhibited non-Nernstian responses over the concentration range of 10^-7-10^-3molL^-1, with LODs of 10.07, 6.90, and 4.30µgL^-1, respectively, as well as average slopes of 39.1, 27.2 and 33mV/decade, respectively. The application of the proposed sensors to the determination of the dinotefuran levels in spiked soil and cucumber samples was demonstrated. The average recoveries from the cucumber samples were from 7.93% to 106.43%, with a standard deviation of less than 13.73%, and recoveries from soil samples were from 97.46% to 108.71%, with a standard deviation of less than 10.66%. The sensors were applied successfully to the determination of the dinotefuran residue, its rate of disappearance and its half-life in cucumbers in soil in which a safety pre-harvest interval for dinotefuran was suggested.

First Electrochemical Method of Nitrothal-Isopropyl Determination in Water Samples

The aim of the research was the use of square wave adsorptive stripping voltammetry (SWAdSV) in conjunction with a hanging mercury drop electrode (HMDE) for the determination of nitrothal-isopropyl. It was found that optimal SW technique parameters were frequency, 200 Hz; amplitude, 50 mV; and step potential, 5 mV. Accumulation time and potential were studied to select the optimal conditions in adsorptive stripping voltammetry: 45 s at 0.0 V, respectively. The calibration curve (SWSV) was linear in the nitrothal-isopropyl concentration range from 2.0 × 10−7 to 2.0 × 10−6 mol L−1 with detection limit of 3.46 × 10−8 mol L−1. The repeatability of the method was determined at a nitrothal-isopropyl concentration level equal to 6.0 × 10−7 mol L−1 and expressed as RSD = 5.5% (n=6). The proposed method was successfully validated by studying the recovery of nitrothal-isopropyl in spiked environmental samples.