On-line SPE and determination of zearalenone from edible oil

Significance of the Topic

The presence of zearalenone, a lipophilic mycotoxin with estrogenic activity, in edible oils represents a significant food safety concern. Regulatory limits set by the European Union and the toxin’s propensity to concentrate in oil matrices underscore the need for reliable, automated analysis methods capable of meeting stringent sensitivity and selectivity requirements.

Objectives and Overview of the Study

This work aimed to develop, optimize, and validate an on-line HPLC method that integrates dynamic covalent hydrazine chemistry (DCHC) for selective trapping of zearalenone (ZON) and a standard reversed-phase SPE trapping step. The goal was to achieve high recoveries, low detection limits, and cartridge reusability in edible oil matrices.

Methodology and Instrumentation

Sample Preparation and SPE Workflow:

• Dilute edible oil (0.70–0.74 g) in heptane to 1 mL.
• Dynamic covalent coupling of ZON to a sulfonyl-hydrazine cartridge via circulatory pumping (60 min).
• Sequential washes with isopropanol and acetonitrile to remove triglycerides and transition to aqueous conditions.
• Cleavage of ZON using 20 % acetone to release the toxin from the hydrazine phase.
• Concentration of released ZON onto a C18 trap cartridge (Eurospher II C18P) by reversed-phase adsorption.
• Gradient elution (30–60 % acetonitrile over 20 min) on an analytical Eurospher II C18P column at 40 °C with fluorescence detection (Ex 276 nm, Em 456 nm).

Used Instrumentation:

• KNAUER AZURA Assistants with high-pressure switching valves and SPE solvent pump
• KNAUER AZURA P6.1L high-pressure gradient pump
• Autosampler unit
• Fluorescence detector RF-20 Axs
• Eurospher II C18P columns for both trap (30×3 mm) and analytical (150×3 mm)

Main Results and Discussion

Method Performance:

• Recovery in methanol model: 95 %; in corn oil: ≈80 %, meeting EU criteria (70–120 %).
• Limit of detection: 1.5 ng on column; linear calibration range 5–100 ng (r2 > 0.9999).
• Hydrazine cartridge reuse: ≥12 cycles with consistent recoveries.
• Chromatograms free of coeluting matrix peaks within ZON retention window.

Benefits and Practical Applications

This automated on-line SPE-HPLC approach:

• Eliminates labor-intensive liquid–liquid extraction and GPC steps.
• Offers high selectivity for non-polar mycotoxins in oil matrices.
• Delivers cost savings through cartridge reuse.
• Adapts to standard HPLC systems for routine QA/QC and regulatory monitoring.

Future Trends and Potential Uses

Emerging directions include multiplexed DCHC approaches for simultaneous mycotoxin profiling, miniaturized high-throughput platforms, and extension to other lipid-rich foods or biofluids requiring selective non-polar analyte enrichment.

Conclusion

The integration of dynamic covalent hydrazine chemistry with on-line reversed-phase SPE and HPLC-FLD offers a robust, sensitive, and fully automated solution for quantifying zearalenone in edible oils. The method meets regulatory performance criteria and streamlines routine analysis workflows.

References

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