DETERMINATION OF PESTICIDES IN EDIBLE OILS BY GC-MS/MS

Importance of the Topic

Determining pesticide residues in edible oils is critical for food safety and regulatory compliance. Oils such as olive oil present analytical challenges due to their high lipid content, which can contaminate and degrade gas chromatography columns and liners. Developing efficient, robust, and greener methods enhances routine monitoring in quality control and research laboratories.

Objectives and Study Overview

This study evaluates a simplified, solvent-saving workflow for quantifying 150 pesticides in olive oil. Two sample-preparation strategies are compared: a reference method based on hexane defatting and GPC cleanup replaced by SPE pass-through (Method 1), and a greener variant using a freeze-out defatting step instead of hexane (Method 2). Both are assessed against SANTE guidelines and a procedural standards calibration approach.

Methodology

An aliquot of olive oil was spiked with target pesticides before extraction. Method 1 employed acetonitrile extraction, freeze-out defatting replaced GPC, and SPE pass-through cleanup with Oasis PRiME HLB cartridges. Method 2 further eliminated nonpolar solvents by substituting hexane defatting with a freezing step to precipitate lipids. Extracts were analyzed by GC-EI-MS/MS on a Xevo TQ-GC system with triphenyl phosphate as internal standard.

Used Instrumentation

• Xevo TQ-GC GC-EI-MS/MS system
• Oasis PRiME HLB SPE cartridges
• Standard gas chromatograph with electron impact ionization

Results and Discussion

Replacing hexane with a freeze-out step improved recoveries for organochlorine pesticides. Method 1 recoveries for compounds like aldrin and hexachlorobenzene were below 30%, while Method 2 achieved recoveries up to 60%. SPE cleanup consistently delivered over 70% recovery for all analytes. Procedural standards calibration corrected for low extraction efficiencies, raising measured recoveries for challenging analytes to near 100% trueness without changing actual extraction yields.

Benefits and Practical Applications

• Reduced solvent consumption and waste through freeze-out defatting.
• SPE pass-through cleanup simplifies workflow and protects GC columns.
• Procedural standards improve quantitation accuracy in complex matrices.
• Sensitivity to 0.005 mg/kg achieved for the most challenging pesticides.

Future Trends and Potential Applications

Further optimization could include automation of freeze-out and SPE steps to increase throughput. Expanding the method to other high-fat food matrices and integrating high-resolution MS may enhance selectivity. Green chemistry approaches, such as supercritical fluid extraction, could further reduce environmental impact.

Conclusion

The study presents a greener, efficient GC-MS/MS method for multi-residue pesticide analysis in edible oils. Freeze-out defatting and SPE cleanup provide robust performance, and procedural standards calibration ensures accurate quantitation in challenging matrices.

References

• European Union (2017), SANTE 11813/2017 Guidance Document on Analytical Quality Control and Method Validation Procedures for Pesticide Residues Analysis in Food and Feed.