Review of thin-layer chromatography in pesticide analysis: 2014–2016

Aptamer-based biosensors for the detection of neonicotinoid insecticides in environmental samples: A systematic review

Neonicotinoids, sometimes abbreviated as neonics, represent a class of neuro-active insecticides with chemical similarities to nicotine. Neonicotinoids are the most widely adopted group of insecticides globally since their discovery in the late 1980s. Their physiochemical properties surpass those of previously established insecticides, contributing to their popularity in various sectors such as agriculture and wood treatment. The environmental impact of neonicotinoids, often overlooked, underscores the urgency to develop tools for their detection and understanding of their behavior. Conventional methods for pesticide detection have limitations. Chromatographic techniques are sensitive but expensive, generate waste, and require complex sample preparation. Bioassays lack specificity and accuracy, making them suitable as preliminary tests in conjunction with instrumental methods. Aptamer-based biosensor is recognized as an advantageous tool for neonicotinoids detection due to its rapid response, user-friendly nature, cost-effectiveness, and suitability for on-site detection. This comprehensive review represents the inaugural in-depth analysis of advancements in aptamer-based biosensors targeting neonicotinoids such as imidacloprid, thiamethoxam, clothianidin, acetamiprid, thiacloprid, nitenpyram, and dinotefuran. Additionally, the review offers valuable insights into the critical challenges requiring prompt attention for the successful transition from research to practical field applications.

Aptamer-modified paper-based analytical devices for the detection of food hazards: Emerging applications and future perspective

Food analysis plays a critical role in assessing human health risks and monitoring food quality and safety. Currently, there is a pressing need for a reliable, portable, and quick recognition element for point-of-care testing (POCT) to better serve the demands of on-site food analysis. Aptamer-modified paper-based analytical devices (Apt-PADs) have excellent characteristics of high portability, high sensitivity, high specificity, and on-site detection, which have been widely used and concerned in the field of food safety. The article reviews the basic components and working principles of Apt-PADs, and introduces their representative applications detecting food hazards. Finally, the advantages, challenges, and future directions of Apt-PADs-based sensing performance are discussed, to provide new directions and insights for researchers to select appropriate Apt-PADs according to specific applications.

Synthesized novel chromogenic reagent and sensor: Detection and identification of dichlorvos

We developed a novel chromogenic reagent and sensor by selective approach, for the detection and identification of dichlorvos, which we tested with the thin layer chromatography method. For the first time, we reported in situ-generated glyoxal as a hydrolysis product, which then interacts with isoniazid to produce a yellow-colored cyclic compound. We used well-known spectroscopic techniques to confirm the chemical identity of the final product. We initially investigated the reaction using a variety of approaches, followed by attempts to establish the reaction mechanism using Density Functional Theory by Gaussian software.

Determination of carboxylesterase by fluorescence probe to guide detection of carbamate pesticide

A carboxylesterase fluorescent probe (Probe 1) was developed for determination of carboxylesterase to guide detection of carbamate pesticide. The probe uses benzothiazole as fluorescence group and phenyldimethyl carbamate as recognition group. The solution of the fluorescent probe gradually changes from light blue to dark blue as the concentration of carbamate pesticides increases. The concentration of carbamate pesticides can be quickly calculated according to the colour of the probe solution through Get Color software on a smartphone. It showed that Probe 1 can be used as a rapid detection tool to achieve rapid detection of carbamate pesticides in juice samples without professional personnel and equipment. Furthermore, the probe has been successfully used to detect carbamate pesticides in fruit juice and vegetable juice.

Ultrasensitive detection of thiram based on surface-enhanced Raman scattering via Au@Ag@Ag core/shell/shell bimetallic nanorods

We developed a highly sensitive and stable SERS-active substrate of Au@Ag@Ag core/shell/shell nanorods, formed by encapsulating Au nanorods (Au NRs) into a bilayer silver shell with Raman reporter molecules (4-mercaptobenzoic acid (4-MBA) and thiram) in the shell-shell gap. The core/shell/shell nanostructures demonstrated a high SERS enhancement and easy assembly. The important role of the bilayer silver shell in boosting the SERS intensity and detection sensitivity was revealed by comparing the performances of the Au@Ag@4-MBA@Ag NRs, Au@Ag@4-MBA NRs, and Au@4-MBA NRs. The obtained Au@Ag@4-MBA@Ag NRs exhibited a significantly promoted SERS intensity, which could reach around 2.6 times and 240 times that of the Au@Ag@4-MBA NRs and Au@4-MBA NRs, where the enhancement factor was found to be strongly correlated with the shell thickness. The controllable plasma properties and SERS effect of the Au@Ag@4-MBA@Ag NRs could be optimized by adjusting the dose of silver nitrate. The SERS substrate comprising core/shell/shell nanorods was highly reproducible and stable (retaining 83% SERS intensity after one month). Moreover, the highly sensitive detection of the pesticide thiram with a detection limit as low as 1.74 × 10-9 M was achieved by taking advantage of the great SERS response of the core/shell/shell nanostructures, which was 1-2 orders of magnitude lower than for other SERS substrates. The developed SERS substrate could be readily extended to embed other target analytes into the core/shell/shell nanostructure for novel and sensitive detection. This study could enable fresh approaches toward next-generation ultrasensitive analyte detection.

A method for the rapid determination of pesticides coupling thin-layer chromatography and enzyme inhibition principles

Herein, we developed a method coupling TLC and enzyme inhibition principles to rapidly detect OPs (dichlorvos, paraoxon and parathion). After the removal of the organic solvent from the samples using TLC and paper-based chips, the enzyme was added to the detection system. The results showed that the current method effectively reduced the effects of solvents on enzyme behavior. Moreover, the pigments could be successfully retained on TLC with 40% ddH₂O/ACN solution (v/v) as a developing solvent. Additionally, the detection limits (LODs) were 0.002 µg/mL for dichlorvos, 0.006 µg/mL for paraoxon, and 0.003 µg/mL for parathion. Finally, the method was applied to spiked cabbage, cucumber, and spinach and showed good average recoveries ranging between 70.22% and 119.79%. These results showed that this paper-based chip had high sensitivity, precleaning, and elimination of organic solvent properties. Furthermore, it provides a valuable idea for sample pretreatment and rapid determination of pesticide residues in food.

Rapid method for detection, quantification and measuring microbial degradation of pesticide-thiram using high performance thin layer chromatography (HPTLC)

Thiram (tetramethylthiuramdisulfide) or thiram sulphide is a dithiocarbamate group of non-systemic group of fungicide which are applied for seed treatment, control of the crop pests, to repel animals, etc. Moreover, thiram has also been responsible to cause moderate skin sensitivity and eye irritation. Higher exposure to thiram might also lead to developmental damages to newborn and neurotoxic effects to non-target organisms. Advancing to prevent such toxic effects and prevention of soil fertility from thiram and thiram-like chemicals is indispensable. The analytical High-Performance Thin-Layer Chromatography (HPTLC) is a simple, quick and a reliable method was proposed and validated for the detection and quantification of various small molecules for many years. This manuscript represents the solution to use microbes to degrade the thiram present in the soil and for that, HPTLC based method to study thiram degradation by Pseudomonas has been designed. Herein, a HPTLC protocol formalised to reveal the detection and quantification of thiram within the range of 100 to 700 ng/spot on TLC plate. The same concentration was then used for calculating percent microbial degradation of thiram from the culture broth. To perform the microbial degradation of thiram, Pseudomonas otitidis strain TD-8 and Pseudomonas stutzeri strain TD-18 were taken as thiram degrader microbial strain. The efficacy of TD-8 to degrade thiram was identified to be 81 and 99% when grown in presence of thiram for 4 days and 8 days, respectively, while TD-18 strain's efficacy to degrade thiram was found to be 57% and 99% when grown in presence of thiram for 4 days and 8 days, respectively.

Determination of Pesticide Residue in Brinjal Sample Using HPTLC and Developing a Cost-Effective Method Alternative to HPLC

Two analytical techniques HPLC (high performance liquid chromatography) and HPTLC (high performance thin layer chromatography) were validated to reveal the quality and quantity of pesticide residues (organophosphorus, organochlorine, and pyrethroids) in brinjal samples collected from a local market of Faisalabad. The HPTLC methods showed linear behavior for standard samples and residue was in the range of 1–130 ng. The organochlorine (α-endosulfan) contaminates the samples at 4, 5, 9, and 10 weeks, and detected quantity was less than MRL (minimum residue level) of the FAO (Food and Agriculture Organization of United Nations), i.e., 0.5 mg·kg−1. The organophosphorus pesticide (chlorpyriphos, methamidophos, monocrotophos, dichlorvos, carbosulfan, profenophos, and dimethoate) residue contaminated the samples and violated the MRL limit. Pyrethroids (deltamethrin, β-cyhalothrin, and cypermethrin) were present at appreciable levels, in samples of 1, 3, 4, 6, 8, and 9 weeks. The concentration of β-cyhalothrin (0.25 mg·kg−1) and cypermethrin (0.205 mg·kg−1) was significantly higher than that of all detected pesticides. The carbosulfan and deltamethrin contaminated all 10-week samples. The HPLC analysis of samples was carried out to confirm the efficiency of HPTLC as cost-effective method. The concentration of α-endosulfan, chlorpyriphos, dimethoate, monocrotophos, profenophos, deltamethrin, and cypermethrin in brinjal samples through the HPTLC method showed similar residual concentration with HPLC analysis.

4-Mercaptobenzoic Acid Labeled Gold-Silver-Alloy-Embedded Silica Nanoparticles as an Internal Standard Containing Nanostructures for Sensitive Quantitative Thiram Detection

In this study, SiO2@Au@4-MBA@Ag (4-mercaptobenzoic acid labeled gold-silver-alloy-embedded silica nanoparticles) nanomaterials were investigated for the detection of thiram, a pesticide. First, the presence of Au@4-MBA@Ag alloys on the surface of SiO2 was confirmed by the broad bands of ultraviolet-visible spectra in the range of 320-800 nm. The effect of the 4-MBA (4-mercaptobenzoic acid) concentration on the Ag shell deposition and its intrinsic SERS (surface-enhanced Raman scattering) signal was also studied. Ag shells were well coated on SiO2@Au@4-MBA in the range of 1-1000 µM. The SERS intensity of thiram-incubated SiO2@Au@4-MBA@Ag achieved the highest value by incubation with 500 µL thiram for 30 min, and SERS was measured at 200 µg/mL SiO2@Au@4-MBA@Ag. Finally, the SERS intensity of thiram at 560 cm-1 increased proportionally with the increase in thiram concentration in the range of 240-2400 ppb, with a limit of detection (LOD) of 72 ppb.