Multipesticides Residue Determination in Fresh Okra Using QuEchERS Sample Preparation and Gas Chromatography Tandem Mass Spectrometry

Significance of the topic

Pesticide residue monitoring in vegetables like okra is vital to ensure compliance with food safety regulations and to protect consumer health. Okra's high water content and presence of mucilage and pigments pose analytical challenges that demand efficient sample preparation for reliable quantification at trace levels.

Objectives and overview of the study

The study aimed to establish a rapid, cost-effective QuEChERS-based sample preparation protocol coupled with gas chromatography–tandem mass spectrometry (GC–MS/MS) to simultaneously quantify multiple pesticide residues in fresh okra. Key goals included optimizing extraction and cleanup steps to maximize recovery while minimizing matrix interferences and instrument contamination.

Methodology and instrumentation

A modified QuEChERS procedure was applied: fresh okra was homogenized, hydrated with water, then extracted with 1% acetic acid in acetonitrile. Phase separation was induced by adding magnesium sulfate and sodium acetate, followed by centrifugation. The acetonitrile layer underwent dispersive solid-phase extraction using PSA, C18, graphitized carbon black, and MgSO4 to remove pigments and mucilage.

Instrumentation

• Gas chromatograph with capillary flow technology and mid-column backflush
• Agilent 7000 Series triple-quadrupole mass spectrometer in electron ionization and SRM mode
• HP-5MS capillary column (15 m × 0.25 mm, 0.25 µm)
• Agilent 7693A autosampler and multimode inlet with splitless injection

Results and discussion

Validation at spiking levels of 10, 25, and 50 ng/g demonstrated recoveries between 70–120% and relative standard deviations below 20% for the majority of the 90 monitored pesticide compounds, meeting EU DG SANCO criteria. A subset of analytes showed lower recoveries but maintained acceptable repeatability and could be corrected via recovery factors. Method sensitivity allowed quantification down to 1–3 ng/g. Application to market samples from Tamil Nadu and Karnataka revealed multiple pesticide residues, highlighting the method’s suitability for routine surveillance.

Benefits and practical applications

• High throughput workflow with minimal solvent and consumable use
• Effective removal of interfering pigments and mucilage extends column and liner life
• Compliance with international regulatory standards for pesticide analysis in export commodities
• Applicability to routine quality control in research, industrial, and regulatory laboratories

Future trends and opportunities

Integration of high-resolution mass spectrometry and automated data processing can further enhance compound coverage and identification confidence. Development of greener sorbents and reduced solvent protocols will improve sustainability. Miniaturized extraction systems and on-site screening tools may expand monitoring capabilities in the field.

Conclusion

The validated QuEChERS–GC–MS/MS approach provides a robust, sensitive, and efficient solution for multi-residue pesticide analysis in complex okra matrices. Its compliance with stringent recovery and precision criteria supports its adoption for regulatory and industrial monitoring of fresh produce.

References

• APEDA procedure for agrochemical control in okra export (2013)
• Agilent Technologies. QuEChERS Sample Preparation Manual, Pub. 5991-1057EN.
• Woolfe ML, Chaplid MF, Otchere G. Studies on mucilage extraction from okra and baobab leaves. University of Ghana.
• Agilent Pesticides and Environmental SRM Database, P/N G9250AA.
• European Commission DG SANCO. Guidance Document on Analytical Quality Control and Method Validation (2013).