Analysis of Organochlorine Pesticide Residues in Whole Milk Using QuEChERS Followed by Enhanced Matrix Removal—Lipid Cleanup by GC-MS/MS

Importance of the topic

Milk and other fatty food matrices often accumulate persistent organic pollutants such as organochlorine pesticides (OCPs), posing significant health risks due to their toxicity and bioaccumulation. Reliable, high-throughput methods for OCP analysis in high-fat samples are essential for food safety monitoring and regulatory compliance.

Objectives and study overview

The study aimed to develop and validate a simple, rapid extraction and cleanup workflow combining QuEChERS extraction with enhanced matrix removal—lipid (EMR–Lipid) dispersive solid-phase extraction (dSPE) to improve recovery and quantitation of 21 key OCPs in whole milk using GC-MS/MS. Benchmarking focused on recovery, precision, limits of quantitation, and matrix effects.

Methodology and instrumentation

Sample preparation:

• 10 mL whole milk spiked at 5–50 ng/mL
• Ethyl acetate and acetonitrile extraction (9:1), QuEChERS EN salt packet
• EMR–Lipid dSPE cleanup: 2 mL water activation, lipid removal by size exclusion and hydrophobic trapping
• Polish step with MgSO4 and final acidification with 1% formic acid

Instrumentation:

• Agilent 7890B GC with multimode inlet and dual DB-5ms Ultra Inert columns
• Agilent 7000C Triple Quadrupole MS in MRM mode
• Instrument control and data analysis via MassHunter software

Main results and discussion

The EMR–Lipid protocol achieved:

• Recoveries of traditionally challenging OCPs (cis-chlordane, 4,4'-DDE, 4,4'-DDT, Endrin, HCB) between 74% and 88% at 10 ng/mL, exceeding SANCO guidelines by 25–40%
• Linearity (R2 > 0.99) over 0.5–100 ng/mL
• Limits of quantitation ≤ 5 ng/mL with <20% RSD
• Reduced matrix interferences, improved signal-to-noise, and stable instrument performance

Benefits and practical application

The combined QuEChERS/EMR–Lipid approach enhances throughput, minimizes solvent and consumable use, and significantly lowers GC-MS/MS maintenance by preventing lipid buildup. It meets regulatory criteria for OCP monitoring in milk and is adaptable to other fatty matrices.

Future trends and opportunities

Further integration with automated extraction platforms and expansion to broader classes of lipophilic contaminants is anticipated. Emerging sorbent chemistries and miniaturized cleanup formats could drive even faster, greener workflows for complex food and environmental samples.

Conclusion

The study demonstrates that QuEChERS extraction followed by EMR–Lipid dSPE provides a robust, high-recovery, and reliable method for GC-MS/MS analysis of organochlorine pesticides in whole milk. The workflow satisfies stringent regulatory requirements while improving laboratory efficiency.

References

1. European Commission SANCO/11945/2015 Guidance Document on Analytical Quality Control and Validation Procedures for Pesticide Residues Analysis in Food and Feed
2. Gilbert-López B. et al., Talanta 2009, 79, 109–128
3. USDA Pesticide Data Program