Trace Detection of Diphenylamine in Baby Food

Significance of the Topic

Diphenylamine (DPA) functions as an antioxidant and dye fixative in postharvest produce treatment and industrial processes. Its residue levels are tightly controlled by regulators, especially in processed baby foods. Ensuring accurate trace detection of DPA in infant food matrices is critical to safeguarding child health and meeting strict maximum residue limits.

Goals and Overview of the Study

The study aims to demonstrate a rapid, sensitive surface-enhanced Raman spectroscopy (SERS) method using the Metrohm Instant SERS Analyzer (MISA) for detecting DPA in pureed pears marketed as baby food. Key objectives include establishing a reference spectrum, validating detection limits down to regulatory thresholds, and proposing a field-deployable protocol.

Used Methodology and Instrumentation

Samples containing known DPA concentrations (1–100 µg/g) were prepared by spiking pureed pear and extracting with chloroform. The chloroform phase was isolated, dried, and reconstituted with gold nanoparticles (Au NPs) and NaCl to induce SERS signal enhancement. Spectral acquisition was performed using MISA under controlled laser power and integration settings.

Used Instrumentation

• Metrohm Instant SERS Analyzer (MISA Advanced, firmware 0.9.33, software Misa Cal V1.0.15)
• MISA Vial Attachment (6.07505.040)
• ID Kit – Au NP (6.07506.440) including gold nanoparticle colloid, spatula, droppers, vials
• ASTM calibration standard, USB connectivity, and battery-powered housing

Main Results and Discussion

Baseline-corrected SERS spectra exhibited distinct DPA peaks, enabling detection down to 1 µg/g. Overlaid spectra confirmed consistent signal resolution across concentrations. The proposed field protocol—simple extraction, drying, colloid addition, and direct measurement—yielded reproducible results compatible with on-site testing.

Benefits and Practical Applications

• High sensitivity and selectivity for DPA at regulatory levels
• Rapid analysis (<10 minutes) without complex laboratory infrastructure
• Portability supports on-site quality control and occupational exposure monitoring
• Adaptable to diverse food matrices and potential extension to other contaminants

Future Trends and Opportunities

• Development of tailored SERS substrates for broader analyte coverage
• Integration of automated sample handling and data analysis workflows
• Expansion of spectral libraries to include emerging food contaminants
• Deployment in digital traceability systems for real-time food safety monitoring

Conclusion

The MISA SERS method offers a reliable, field-deployable solution for trace-level detection of diphenylamine in infant food. Its ease of use, sensitivity, and portability address critical needs in food safety monitoring and help ensure compliance with stringent residue limits.

References

• Metrohm AG. Trace Detection of Diphenylamine in Baby Food, Application Note AN-RS-026.