Analysis of Illegal Dyes in Food Matrices using Automated Online Sample Preparation with LC/MS

Importance of the Topic

Sudan dyes are synthetic azo compounds banned in food due to carcinogenicity and health concerns, yet they have been detected in chili-based sauces, necessitating sensitive and rapid analytical methods for food safety enforcement.

Objectives and Study Overview

This study aimed to create an automated online sample preparation method coupled with liquid chromatography and high-resolution mass spectrometry to detect and quantify five illegal dyes (Sudan I–IV and Para Red) in various sauce matrices, while reducing manual steps and improving throughput.

Methodology and Instrumentation

Sample preparation involved extraction of homogenized sauce with acetonitrile, vortexing, sonication, centrifugation, and filtration. Online cleanup was performed using a Thermo Scientific Transcend TLX-1 system with TurboFlow XL C8 column, followed by separation on an Accucore Phenyl-Hexyl column and detection using a Thermo Scientific Exactive Orbitrap with heated electrospray ionization in positive mode. The total LC run time was six minutes.

Main Results and Discussion

Limits of quantitation ranged from 5 to 20 ng/g (50 ng/g for Para Red in one matrix) with coefficients of variation below 15% at LOQ. Calibration curves exhibited r2 values above 0.99 over 5–1000 ng/g. Precision tests at 100 ng/g across four sauce types showed RSDs below 10%, and recoveries were within 80–120%. Minimal matrix effects were observed, and all analytes eluted within one minute, enabling potential multiplexed analysis of over 30 samples per hour.

Benefits and Practical Applications

The integrated automated method reduces manual labor, solvent use, and analysis time while providing high sensitivity and selectivity, making it suitable for regulatory and quality control laboratories monitoring food safety.

Future Trends and Applications

Future work may expand the method to additional illegal dyes, adopt ultrahigh-performance columns for faster separations, and implement multiplexed workflows for large-scale screening in diverse food matrices.

Conclusion

The developed automated LC–MS approach using TurboFlow online extraction and Orbitrap detection delivers a rapid, robust, and high-throughput solution for the determination of banned Sudan dyes in complex food samples.

References

1 U.S. Code of Federal Regulations Title 21 Part 73 Subpart A
2 Commission Decision 2003/460/EC on emergency measures regarding hot chili products
3 Commission Decision 2004/92/EC on chili products
4 Rebane R., Leito I., Yurchenko S., Herodes K. Review of Analytical Techniques for Determination of Sudan I–IV Dyes in Food Matrices. J Chromatogr A. 2010;1217:2747–2757
5 Gilbert J. Analytical Challenges in Food Safety: Advances in Instrumental Methods for Food Analysis. Go-Global Seminar, Bangkok, 2007