Surreal illustration of chlorothalonil molecule in a teacup.

Is Chlorothalonil Lurking in Your Tea? A New Way to Detect This Fungicide

"Scientists develop a rapid electrochemical method for detecting chlorothalonil in tea, ensuring safer sips for everyone."


In today's world, the presence of contaminants in food and beverages is a growing concern. Among these, endocrine disruptors (DEs), which include certain pesticides, pose a significant threat due to their ability to interfere with hormonal systems in both humans and animals. These substances accumulate in the environment, affecting ecosystems and potentially causing long-term health issues. Therefore, accurate and efficient methods for monitoring pesticides are more critical than ever to safeguard public health and environmental integrity.

Chlorothalonil (CTL), a widely used organochlorine fungicide, is frequently found in agriculture to protect crops from fungal diseases. It's used on everything from vegetables and fruits to turf and ornamental plants. Unfortunately, CTL is classified as a category II toxic substance by the U.S. Environmental Protection Agency (EPA), indicating it's moderately toxic. Regulatory bodies like the Brazilian National Health Surveillance Agency (ANVISA) set maximum residue levels (MRLs) for CTL in various agricultural products to mitigate potential health risks, underscoring the need for continuous and improved monitoring techniques.

Conventional methods for detecting CTL in environmental and food samples often involve chromatographic and spectroscopic techniques, which can be time-consuming and costly. Given these limitations, there's a growing demand for rapid, cost-effective, and on-site detection methods. This has spurred the development of electroanalytical techniques, which offer quick and portable solutions for pesticide detection. One promising approach involves using boron-doped diamond electrodes (BDDs), known for their wide potential range, high stability, and low adsorption properties, to enhance the detection sensitivity and accuracy of CTL.

How Does the New Electrochemical Method Work?

Surreal illustration of chlorothalonil molecule in a teacup.

Researchers have developed a straightforward electroanalytical method using boron-doped diamond electrodes (BDDs) for the rapid detection of chlorothalonil. This method leverages square-wave voltammetry (SWV) to analyze samples, providing a fast and direct approach to pesticide detection. Here’s a breakdown of the process:

The technique involves observing the electrochemical behavior of chlorothalonil at a BDD electrode within a specific pH range. The study found that in a pH range of 8.0 to 10.0, chlorothalonil exhibits three distinct reduction peaks, which occur at approximately -1.07 V, -1.2 V, and -1.4 V (vs. Ag/AgCl). These peaks indicate reduction processes related to the compound's molecular structure.

  • Electrode Pre-treatment: The BDD electrode undergoes pre-treatment, involving both anodic and cathodic conditioning, to optimize the surface for chlorothalonil detection.
  • Square-Wave Voltammetry: SWV is performed to identify the reduction peaks of chlorothalonil. Parameters such as pulse amplitude, frequency, and step potential are optimized to enhance sensitivity.
  • Data Analysis: The peak currents from the voltammograms are used to create an analytical curve, which plots the concentration of chlorothalonil against the measured current.
To understand the reduction mechanism of chlorothalonil, researchers employed Density Functional Theory (DFT) calculations. DFT, a computational method used in quantum mechanics, helps in studying the electronic structure of molecules. The calculations supported a three-step dehalogenation process, where chlorothalonil undergoes sequential removal of chlorine atoms. The process is facilitated by identifying the most negatively charged carbon atoms, which are the first to undergo dehalogenation.

Why Is This Method Important for Consumers and the Environment?

This research offers a promising step forward in ensuring the safety and quality of our food and environment. By providing a rapid, sensitive, and cost-effective method for detecting chlorothalonil, it supports better monitoring and compliance with safety standards. The electrochemical method using BDD electrodes and SWV is not only effective but also versatile, offering potential for on-site testing and broader application in environmental and food safety monitoring. This innovation contributes to reducing the risks associated with pesticide contamination, promoting healthier ecosystems, and safeguarding public health.

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This article is based on research published under:

DOI-LINK: 10.1007/s10008-018-4162-1, Alternate LINK

Title: Voltammetric Determination Of Chlorothalonil And Its Respective Reduction Mechanism Studied By Density Functional Theory

Subject: Electrical and Electronic Engineering

Journal: Journal of Solid State Electrochemistry

Publisher: Springer Science and Business Media LLC

Authors: Thays Souza Lima, Mauro A. La-Scalea, Cristiano Raminelli, Fábio R. Simões, Edison Franco, Gabriela Dias Da Silva, Michele Aparecida Salvador, Paula Homem-De-Mello, Hueder P. M. De Oliveira, Lúcia Codognoto

Published: 2018-11-28

Everything You Need To Know

1

What is chlorothalonil, and why is it a concern in our food and beverages?

Chlorothalonil (CTL) is a widely used organochlorine fungicide applied in agriculture to protect crops from fungal diseases. It's used on various crops like vegetables, fruits, and ornamental plants. The U.S. Environmental Protection Agency (EPA) classifies CTL as a category II toxic substance, indicating it's moderately toxic. This classification, coupled with the potential for CTL to be an endocrine disruptor (ED), makes its presence in food and beverages a significant health concern. Furthermore, regulatory bodies like the Brazilian National Health Surveillance Agency (ANVISA) set maximum residue levels (MRLs) for CTL in agricultural products to mitigate potential health risks.

2

How does the new electrochemical method detect chlorothalonil in tea, and what are its key components?

The new electrochemical method employs a straightforward electroanalytical approach using boron-doped diamond electrodes (BDDs) for the rapid detection of chlorothalonil. The method utilizes square-wave voltammetry (SWV) to analyze samples. The BDD electrode undergoes pre-treatment, involving anodic and cathodic conditioning, to optimize its surface for chlorothalonil detection. SWV is then performed to identify the reduction peaks of chlorothalonil. The peak currents from the voltammograms are used to create an analytical curve, which plots the concentration of chlorothalonil against the measured current.

3

What are the advantages of using boron-doped diamond electrodes (BDDs) for detecting chlorothalonil?

Boron-doped diamond electrodes (BDDs) offer several advantages for detecting chlorothalonil. They are known for their wide potential range, high stability, and low adsorption properties. This combination enhances the detection sensitivity and accuracy of chlorothalonil, allowing for more reliable and efficient analysis. The use of BDDs enables the development of rapid, cost-effective, and on-site detection methods, which is a significant improvement over conventional chromatographic and spectroscopic techniques that are often time-consuming and expensive.

4

Can you describe the reduction mechanism of chlorothalonil as revealed by Density Functional Theory (DFT) calculations?

Density Functional Theory (DFT) calculations were employed to understand the reduction mechanism of chlorothalonil. The calculations supported a three-step dehalogenation process, where chlorothalonil undergoes sequential removal of chlorine atoms. The process is facilitated by identifying the most negatively charged carbon atoms, which are the first to undergo dehalogenation. This detailed understanding of the molecular behavior aids in optimizing the detection method and understanding the breakdown of the compound.

5

How does this new detection method benefit consumers, and what are the broader implications for environmental monitoring?

This new electrochemical method benefits consumers by providing a rapid, sensitive, and cost-effective way to detect chlorothalonil in food and beverages, which supports better monitoring and compliance with safety standards. The method's versatility also offers potential for on-site testing and broader application in environmental and food safety monitoring. This innovation contributes to reducing the risks associated with pesticide contamination, promoting healthier ecosystems, and safeguarding public health. This approach supports better monitoring and compliance with safety standards and reduces the risks associated with pesticide contamination, promoting healthier ecosystems, and safeguarding public health.

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