Trace Detection of Malathion on Corn

Significance of the Topic

Malathion is commonly applied to various crops to control pests but poses potential health risks at trace levels. Regulatory agencies enforce maximum residue limits (MRLs) as low as 20 ng/g in the EU and 8 µg/g in the US, underscoring the need for sensitive, on-site detection methods.

Objectives and Overview

This study evaluates a portable surface-enhanced Raman spectroscopy (SERS) approach for trace detection of malathion on corn using the MISA (Metrohm Instant SERS Analyzer) platform and gold nanoparticle substrates. The goal is to establish a rapid, user-friendly protocol that meets or exceeds regulatory sensitivity requirements.

Methodology and Instrumentation

Corn kernels were spiked with malathion at concentrations ranging from 1 to 20 µg/g. Analytes were extracted with acetone, dried, and reconstituted with gold colloid and NaCl to promote SERS enhancement. Spectra were acquired using MISA Advanced with Orbital-Raster-Scan technology under a 5 mW laser, 10-second integration time, and ten accumulations.

Used Instrumentation

• MISA Advanced Portable SERS Analyzer (MISA Vial and P-SERS Attachments)
• ID Kit – Gold Nanoparticle Reagents and Consumables

Key Results and Discussion

Baseline-corrected SERS spectra demonstrated reliable detection of malathion on corn at levels down to 5 µg/g. Interference from matrix components and the SERS substrate was observed at low concentrations, highlighting the importance of optimized sample preparation and spectral libraries for accurate identification.

Benefits and Practical Applications

• Portable and battery-operated for field deployment
• Minimal chemical requirements and green extraction solvents
• Rapid analysis with user-friendly software interface
• Sensitivity aligned with regulatory MRLs for food safety screening

Future Trends and Potential Applications

Advances may include improved nanoparticle substrates for lower detection limits, integration of multiplexed libraries for simultaneous screening of multiple pesticides, and coupling with data analytics and machine learning to enhance field decision support.

Conclusion

The MISA-based SERS protocol offers a cost-effective, rapid, and sensitive solution for on-site malathion screening on agricultural products. Its performance meets critical regulatory thresholds, supporting enhanced food safety monitoring.