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Determination of chlorothalonil in difficult-to-analyse vegetable matrices using various multiresidue methods.
N Belmonte Valles1, M Retamal, M A Martínez-Uroz
1European Union Reference Laboratory for Pesticide Residues in Fruits and Vegetables, Pesticide Residue Research Group, University of Almería, 04120 Almería, Spain.
The Analyst
|April 14, 2012
Summary
Determining chlorothalonil in vegetables is challenging due to low recoveries with common methods. The Dutch mini-Luke method, coupled with GC-MS/MS, offers superior recovery and detection limits for accurate pesticide analysis.
Area of Science:
- Analytical Chemistry
- Food Safety
- Environmental Science
Background:
- Chlorothalonil determination in vegetables like leek and garlic presents challenges due to low recovery rates with standard multi-residue methods (MRMs).
- These issues, stemming from high matrix interactions, were highlighted by significant false negatives in proficiency testing for pesticide residues.
- Accurate quantification is crucial for ensuring food safety and compliance with regulatory standards.
Purpose of the Study:
- To evaluate and compare the effectiveness of different MRMs for chlorothalonil determination in vegetable matrices.
- To assess the performance of Gas Chromatography-Mass Spectrometry/Mass Spectrometry (GC-MS/MS) using both electron impact ionization (EI) and negative chemical ionization (NCI) modes.
- To identify an optimal method for reliable chlorothalonil analysis in compliance with EU guidelines.
Main Methods:
- Comparative analysis of three MRMs: ethyl acetate, Dutch mini-Luke, and QuEChERS.
- Utilized GC-MS/MS with both EI and NCI ionization modes for chlorothalonil detection.
- Experiments included leek, garlic, and tomato matrices to assess method performance across different food types.
Main Results:
- The Dutch mini-Luke method yielded the best recoveries (100-120%) with relative standard deviation (RSD) below 20%.
- Ethyl acetate method showed moderate recoveries (52-70%), while QuEChERS provided no recovery.
- Negative chemical ionization (NCI) offered 5-10 times lower limits of detection (LODs) compared to electron impact ionization (EI), with both modes achieving LODs below 10 μg kg(-1).
Conclusions:
- The Dutch mini-Luke method is highly effective for chlorothalonil determination in challenging matrices like leek and garlic.
- GC-MS/MS with NCI provides sensitive detection, crucial for meeting regulatory requirements.
- The optimized method ensures accurate and reliable pesticide residue analysis, aligning with EU Analytical Quality Control (AQC) Guidelines.
