Trace Detection of Auramine O in Curry Powder

Importance of the Topic

The detection of unauthorized dyes in food products such as curry powder is critical for consumer safety and regulatory compliance. Auramine O is a banned dye with known carcinogenic and toxic effects that is still illicitly used to intensify the appearance of spices. Rapid on-site screening methods help prevent contaminated products from reaching consumers and support quality control in food supply chains.

Objectives and Overview

This application note illustrates a simple extraction protocol combined with Surface Enhanced Raman Scattering (SERS) using the Metrohm Instant SERS Analyzer (MISA) to detect trace levels of Auramine O in curry powder. The study covers reference spectrum generation, sample preparation, instrument configuration, and sensitivity assessment down to 1 microgram per gram.

Methodology and Instrumentation

The method employs an alkaline extraction of solid samples followed by partitioning into ethyl acetate and mixing with gold nanoparticles to enhance the Raman signal. Key instrumentation includes the MISA Advanced system with Orbital Raster Scan technology and the Au NP ID Kit for nanoparticle reagents. Acquisition parameters such as laser power, integration time, and number of scans are optimized for sensitive detection.

Main Results and Discussion

Baseline corrected SERS spectra show distinct Auramine O peaks, with solvent and pH induced peak shifts. Calibration with spiked samples yields reliable detection at concentrations as low as 1 microgram per gram. Overlaid spectra confirm reproducible signal intensity across a range of spiking levels from 1 to 1000 micrograms per gram, demonstrating both sensitivity and robustness.

Benefits and Practical Applications

MISA provides rapid and accurate on-site screening without the need for complex lab infrastructure. The minimal sample preparation, portability, and user friendly interface make it suitable for field QC in manufacturing, shipping inspections, and regulatory enforcement.

Future Trends and Opportunities

Advances may include integration with spectral libraries and machine learning for automated identification of food adulterants, expansion to other banned dyes, and miniaturized sampling attachments for broader matrix compatibility.

Conclusion

The presented SERS based assay for Auramine O offers a fast, sensitive, and field deployable approach for safeguarding food quality. MISA’s ease of use and low consumable requirements position it as an effective tool for routine surveillance of illicit colorants.