Stability of Selected Pesticides on Solid-Phase Extraction Disks.

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Pesticide Science

Background:

• Accurate pesticide residue analysis is vital for environmental monitoring and food safety.
• Understanding pesticide storage stability is crucial for reliable analytical results.
• Solid-phase extraction (SPE) is a common technique for pesticide sample preparation.

Purpose of the Study:

• To evaluate the storage stability of five common pesticides (2,4-D, triclopyr, carbofuran, molinate, thiobencarb) on C18 SPE disks.
• To compare the stability of pesticides stored on SPE disks versus in cold water.
• To determine the optimal temperature regimes for pesticide storage on SPE disks.

Main Methods:

• Fortification of water samples with a mixture of five pesticides at 20 μg L⁻¹.
• Extraction of pesticides onto C18 SPE disks.
• Storage of extracted pesticides on disks at various temperatures (4°C, -20°C, and a combination).
• Storage of fortified water samples at 4°C for comparison.
• Residue analysis conducted at multiple time points (0, 3, 30, 90, 180 days).

Main Results:

• Pesticides exhibited significantly greater stability when stored on C18 SPE disks compared to cold water storage.
• Carbofuran demonstrated the lowest stability among the tested pesticides, with losses up to 100%.
• Optimal stability (≤20% loss over 180 days) was achieved for 2,4-D, triclopyr, molinate, and thiobencarb on SPE disks at -20°C.
• Storage in water at 4°C resulted in 25-35% pesticide loss over the same period.

Conclusions:

• Storing pesticide extracts on C18 SPE disks, particularly at -20°C, enhances long-term stability.
• This storage method is superior to cold water storage for maintaining pesticide integrity.
• The findings support the use of SPE disk storage for reliable pesticide residue analysis over extended durations.