GC-μECD Analysis and Confirmation of Contract Laboratory Protocol Pesticides in Olive Oil

Significance of the Topic

Olive oil is widely consumed for its nutritional benefits, but its production process can concentrate pesticide residues. Monitoring these residues at trace levels is essential for consumer safety and regulatory compliance. An efficient analytical workflow that combines cost-effectiveness with high sensitivity is therefore critical for routine quality control in the food industry.

Objectives and Study Overview

This study aimed to develop and validate a robust method for simultaneous screening and confirmation of 20 contract laboratory protocol (CLP) pesticides in olive oil. Key goals included achieving low detection limits, reliable quantification, and streamlined sample preparation using commonly available laboratory instrumentation.

Applied Methodology and Instrumentation

The analytical workflow comprised:

• Sample Cleanup: A QuEChERS extraction (acetonitrile partition with MgSO₄/NaCl) followed by dispersive SPE to remove lipophilic interferences.
• Chromatography: Single-injection, dual-column gas chromatography with micro-electron capture detection (GC-µECD).
• Instrument Configuration: Agilent 7890A GC with a two-way capillary flow splitter (CFT), directing effluent to:
  
  • Primary column: Agilent J&W DB-35ms (30 m × 0.25 mm × 0.25 µm).
  • Confirmatory column: Agilent J&W DB-XLB (30 m × 0.25 mm × 0.50 µm).
• Calibration and Standards: CLP pesticide standards (4–40 ng/mL) and surrogate standards (0.5–20 ng/mL) prepared in 2,2,4-trimethylpentane.

Main Results and Discussion

Performance metrics demonstrated:

• Linearity: r² values of 0.994–0.999 across both columns.
• Detection Limits: Average LOD of 0.3 ng/mL (S/N = 3) and LOQ of 1.0 ng/mL (S/N = 10).
• Analysis Time: All 20 pesticides resolved in under 12 minutes on each column.
• Matrix Tolerance: Effective removal of lipid interferences without compromising sensitivity.

Application to a commercial extra-virgin olive oil sample revealed the presence of endosulfan sulfate (23.1 ng/mL) and endosulfan I (7.1 ng/mL). Overlaid chromatograms on both columns confirmed these residues by matching retention patterns between spiked standards and the native sample.

Benefits and Practical Application

The combined single-injection, dual-column GC-µECD approach offers:

• Time and resource savings compared to separate screening and confirmatory runs.
• Low-cost instrumentation relative to mass spectrometry alternatives.
• High throughput suitable for routine quality control laboratories.

Future Trends and Potential Uses

Potential extensions include:

• Adaptation to other high-lipid matrices (e.g., nuts, seeds, fatty fish).
• Integration with alternative detectors (e.g., GC-MS/MS) to broaden analyte scope.
• Automation of the QuEChERS/dSPE workflow to further increase throughput.

Conclusion

This study demonstrates a cost-effective, high-sensitivity method for simultaneous screening and confirmation of 20 pesticide residues in olive oil. The QuEChERS/dSPE cleanup paired with dual-column GC-µECD detection delivers robust performance, making it a practical alternative for routine monitoring and regulatory compliance.

References

1. E. Amvrazi and T. Albanis, Food Chemistry 113 (2009) 253–261.
2. E. Amvrazi and T. Albanis, J. Agric. Food Chem. 54 (2006) 9642–9647.
3. J. Garcia-Reyes et al., Trends Anal. Chem. 26 (2007) 239–251.
4. S. Cunha et al., J. Sep. Sci. 30 (2007) 620–632.
5. D. Smith and K. Lynam, Agilent Technologies 5990-4351EN (2009).
6. C. George, Agilent Technologies 5988-4971EN (2001).