Rapid screening of flonicamid residues in environmental and agricultural samples by a sensitive enzyme immunoassay

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.

Combination of zeolitic imidazolate framework-67 and magnetic porous porphyrin organic polymer for preconcentration of neonicotinoid insecticides in river water

A nanostructured material composed of zeolitic imidazolate framework-67 and magnetic porous porphyrin organic polymer (ZIF-67@MPPOP) was successfully synthesized and applied for the enrichment of neonicotinoid insecticides in river water. The analytes were detected and quantified using high performance liquid chromatography coupled with diode array detector (HPLC-DAD) and liquid chromatography mass spectrometry (LC-MS). Influential experimental parameters were optimized using response surface methodology based on Box Behnken design. The adsorption capacities were 69.46, 80.53, 85.39 and 90.0 mg g^-1 for thiamethoxam, imidacloprid, acetamiprid and clothianidin, respectively. At optimal experimental conditions, low limit of detection (LOD), limit of quantification (LOQ) and linearity were 0.0091-0.04 µg L^-1, 0.04-0.13 µg L^-1 and (0.04-600 µg L^-1), respectively. The relative standard deviation used to evaluate the reproducibility and repeatability of the method was less than 5%. Finally, the method was employed for determination of four neonicotinoid insecticides in river water.

Ultrasensitive monitoring strategy of PCR-like levels for zearalenone contamination based DNA barcode

BACKGROUND

The ultrasensitive monitoring strategy of zearalenone (ZEN) is essential and desirable for food safety and human health. In the present study, a coupling of gold nanoparticles-DNA barcode and direct competitive immunoassay-based real-time polymerase chain reaction signal amplification (RT-IPCR) for ZEN close to the sensitivity of PCR-like levels is described and evaluated.

RESULTS

The RT-IPCR benefited from the use of a DNA barcode and RT-PCR detection strategy, thus resulting in ultrasensitive and simple detection for ZEN. Under the optimal RT-IPCR, the linear range of detection was from 0.5 to 1000 pg mL^-1 and the limit of detection was 0.5 pg mL^-1 , which was 400-fold lower than the enzyme-linked immunosorbent assay. The detection procedure was simplified and the detection time was shortened. The specificity, accuracy and precision of the RT-IPCR confirmed a high performance. ZEN-positive contamination levels were from 0.056 to 152.12 ng g^-1 by the RT-IPCR, which was demonstrated to be highly reliable by liquid chromatography-tandem mass spectrometry.

CONCLUSION

The proposed RT-IPCR could be used as an alternative for detecting ZEN with satisfactory ultrasensitivity, simplicity, low cost and high-throughput. The present study could provide a strategy for the ultrasensitive detection of the small molecule with a simple and practical approach, which has significant appeal and application prospects.

Semi-quantitative and quantitative detection of ochratoxin A in agricultural by-products using a self-assembling immunochromatographic strip

BACKGROUND

The toxicity and health risks of mycotoxins have encouraged increased awareness and strict monitoring of these contaminants in agricultural by-products. In this paper, we developed and tested a sensitive, selective, and self-assembling immunochromatographic (IC) strip for on-site detection of ochratoxin A (OTA). We were able to demonstrate semi-quantitative and quantitative detection of OTA in agricultural by-product samples.

RESULTS

The optimized IC strip had a limit of detection (LOD) of 0.5 ng mL^-1 OTA using the naked eye for semi-quantitative detection. When a digitized strip reader was used to achieve quantitative results, the LOD for OTA was reduced to 0.1 ng mL^-1 with a linear detection range of 0.1-10 ng mL^-1 . We also evaluated the specificity, stability, accuracy, and precision of the IC strip and demonstrated high performance in all of these areas. We then confirmed the ability of the IC strip to visually detect OTA contamination in authentic agricultural by-product samples from the markets in China. Furthermore, quantitative detection of OTA using the IC strip showed that the concentration of OTA ranged from 1.7 to 101.3 ng g^-1 in the positive agricultural by-product samples, correlating well with the measurements obtained via liquid chromatography with tandem mass spectrometry.

CONCLUSION

The results indicated that this proposed IC strip was capable of sensitive, semi-quantitative, quantitative, and on-site detection of OTA contamination in agricultural by-product samples. © 2020 Society of Chemical Industry.

Contamination of Zearalenone from China in 2019 by a Visual and Digitized Immunochromatographic Assay

Zearalenone (ZEN) is a prevalent mycotoxin that needs intensive monitoring. A semi-quantitative and quantitative immunochromatographic assay (ICA) was assembled for investigating ZEN contamination in 187 samples of cereal and their products from China in 2019. The semi-quantitative detection model had a limit of detection (LOD) of 0.50 ng/mL with visual judgment and could be completely inhibited within 5 min at 3.0 ng/mL ZEN. The quantitative detection model had a lower LOD of 0.25 ng/mL, and ZEN could be accurately and digitally detected from 0.25-4.0 ng/mL. The ICA method had a high sensitivity, specificity, and accuracy for on-site ZEN detection. For investigation of the authentic samples, the ZEN-positive rate was 62.6%, and the ZEN-positive levels ranged from 2.7 to 867.0 ng/g, with an average ZEN-positive level being 85.0 ng/g. Of the ZEN-positive samples, 6.0% exceeded the values of the limit levels. The ZEN-positive samples were confirmed to be highly correlated using LC-MS/MS (R² = 0.9794). This study could provide an efficiency and accuracy approach for ZEN in order to achieve visual and digitized on-site investigation. This significant information about the ZEN contamination levels might contribute to monitoring mycotoxin occurrence and for ensuring food safety.

High-Performance Multiporous Imprinted Microspheres Based on N-Doped Carbon Dots Exfoliated from Covalent Organic Framework for Flonicamid Optosensing

High-performance, multiporous imprinted microspheres were prepared from nitrogen-doped carbon dots (N-CDs) using a one-pot reverse microemulsion surface-imprinting method. Here, the N-CDs were exfoliated from a common layer covalent organic framework in a top-down preparation, and an ionic liquid was added to improve the sensitivity and the fluorescence stability. The multiporous imprinted microspheres were successfully applied to flonicamid optosensing in fruits and vegetables with simultaneous analysis of 96 samples by multifunctional enzyme labeling. The fluorescence sensing procedure was performed on recyclable multiporous imprinted microspheres coupling with the interface of N-CDs by taking advantage of the fluorescence-resonance charge-transfer strategy between the N-doped carbon dots and flonicamid molecules, quenching the fluorescence intensity. The multiporous imprinted microspheres exhibited purple fluorescence, which decreased sharply in intensity as the concentration of flonicamid increased. The fluorescence quenching correlation with the concentration of flonicamid showed good linearity in the range of 0.02-0.2 μg g^-1 with a detection limit of 0.0059 μg g^-1. This research not only enriches the foundational study of flonicamid residues but also greatly expands the potential applications of multiporous imprinted microspheres for analysis of pesticide residues in agricultural, food, and environmental monitoring.

Highly efficient detection of salbutamol in environmental water samples by an enzyme immunoassay

Salbutamol (SAL) has potential hazardous effects on health, and has been found in natural water globally. To protect consumers from risks related to SAL residues, a fast and highly sensitive enzyme-linked immunosorbent assay (ELISA) was developed for the detection of SAL in environmental water samples. SAL hapten was synthesized and conjugated to proteins to be used as the immunogen for producing polyclonal antibodies. Under optimized conditions, the ELISA showed a 50% inhibitory concentration (IC₅₀ value) of 0.466μg/L, with a limit of detection (LOD, IC₁₀ value) of 0.021μg/L. The LOD of the ELISA was 5-fold lower than the maximum residue limits. The average recoveries of SAL from environmental samples, including tap water, river water and wastewater, ranged from 80.1 to 115.6%, which is well within the requirements of residue detection. Moreover, the results of the ELISA correlated well with high-performance liquid chromatography results, with a correlation coefficient of 0.988. These results suggest that the proposed ELISA method has potential application for the monitoring of SAL residues in environmental water samples.

Highly efficient detection of paclobutrazol in environmental water and soil samples by time-resolved fluoroimmunoassay

A fast and ultrasensitive indirect competitive time-resolved fluoroimmunoassay (TRFIA) was developed for the analysis of paclobutrazol in environmental water and soil samples. Paclobutrazol hapten was synthesized and conjugated to bovine serum albumin (BSA) for producing polyclonal antibodies. Under optimal conditions, the 50% inhibitory concentration (IC50 value) and limit of detection (LOD, IC20 value) were 1.09μgL(-1) and 0.067μgL(-1), respectively. The LOD of TRFIA was improved 30-fold compared to the already reported ELISA. There was almost no cross-reactivity of the antibody with the other structural analogues of triazole compounds, indicating that the antibody had high specificity. The average recoveries from spiked samples were in the range from 80.2% to 104.7% with a relative standard deviation of 1.0-9.5%. The TRFIA results for the real samples were in good agreement with that obtained by high-performance liquid chromatography analyses. The results indicate that the established TRFIA has potential application for screening paclobutrazol in environmental samples.