Simultaneous Quantification of Pesticide Residues in Olive Oil via LC-MS/MS and GC-MS/MS Using a Streamlined, Automatable cSPE Clean-up Workflow

Importance of the Topic

Olive oil is a key component of many diets worldwide, valued for its health benefits and culinary versatility. Ensuring its safety through accurate detection of pesticide residues is critical to protect consumer health and comply with strict regulatory limits set by agencies such as the European Union.

Objectives and Study Overview

This study aimed to develop and validate a robust, high-throughput analytical workflow for simultaneous quantification of over 200 pesticide residues in olive oil. The approach combined liquid chromatography tandem mass spectrometry (LC-MS/MS) and gas chromatography tandem mass spectrometry (GC-MS/MS) with an automated dispersive solid-phase extraction (cSPE) clean-up, following the SANTE 11312/2021 guidelines.

Methodology and Instrumentation

A streamlined clean-up protocol employed Biotage ISOLUTE cSPE sorbent blends processed on the Biotage Extrahera Classic automated extraction unit. Sample preparation involved:

• Weighing 5 g of oil and extracting with 10 mL acetonitrile;
• Vortex mixing, centrifugation, and transfer of the supernatant through cSPE cartridges;
• Collecting 1 mL eluate for analysis.

The analytical platforms included:

• Shimadzu LCMS-8045RX coupled with an LC-40 series pump for LC-MS/MS quantification
• Shimadzu GCMS-TQ8050 NX for GC-MS/MS analysis

Key chromatographic conditions:

• LC column: 2.1 x 100 mm, 2.7 µm biphenyl; mobile phases water and methanol with ammonium formate and formic acid; gradient from 3 to 100% organic over 12 minutes; flow rate 0.4 mL/min; injection 4 µL; column temperature 35 °C.
• GC column: 30 m x 0.25 mm, 0.25 µm Rtx-5MS; splitless injection of 1 µL; helium carrier gas; oven ramp from 90 °C to 310 °C; ion source at 230 °C, interface 290 °C.

Main Results and Discussion

Matrix-matched calibration exhibited linearity coefficients (R2) ≥ 0.99 for all target compounds. Recovery studies at 10 µg/kg spiking level produced mean recoveries between 70 and 120%, with relative standard deviations below 12%, meeting SANTE criteria. Representative chromatograms demonstrated clear separation and sensitive detection of analytes such as fipronil and metalaxyl. Automation of the cSPE workflow reduced manual variability and improved throughput compared to traditional offline SPE.

Benefits and Practical Applications

This validated method offers:

• High sensitivity and specificity for broad pesticide classes
• Streamlined sample preparation with consistent recoveries
• Compliance with international residue regulations
• Suitability for routine quality control in food, environmental, and research laboratories

Future Trends and Applications

Advancements may include integration of non-targeted screening, expansion of compound libraries, miniaturized extraction formats, and implementation of greener solvents. Further automation and digitalized data workflows are expected to enhance laboratory efficiency and data integrity.

Conclusion

The combination of LC-MS/MS and GC-MS/MS with an automated cSPE clean-up provides a reliable, sensitive, and efficient approach for monitoring pesticide residues in olive oil. This workflow supports high sample throughput and meets regulatory requirements, offering a valuable tool for food safety laboratories.

Reference

1. Hakme E., Uclés S., Parrilla-Vázquez P., Gamón M., Cutillas V., Fernández-Alba A.R. Development and validation of a new multiresidue method for determination of multiclass pesticide residues using GC-QqQ-MS/MS in edible oils.