LC-MS Determination of Sudan Dyes in Chili Oleoresin Using the CORTECS C18, 2.7 μm Column

Significance of the Topic

Chili oleoresin is a concentrated extract widely employed as a natural coloring and flavoring agent in food and pharmaceutical applications. The clandestine addition of Sudan dyes to this matrix poses significant food safety concerns due to their carcinogenic potential. Sensitive and reliable analytical protocols are vital to ensure regulatory compliance and protect public health.

Objectives and Study Overview

• Develop a robust method for the determination of ten common Sudan dyes in chili oleoresin.
• Implement a straightforward solid-phase extraction (SPE) cleanup to handle the complex oleoresin matrix.
• Assess chromatographic performance using a CORTECS C18 solid-core 2.7 µm column compatible with both HPLC and UPLC systems.

Methodology and Instrumentation

Sample preparation:
A 0.1 g chili oleoresin sample was dissolved in hexane and processed via SPE using a Sep-Pak Silica cartridge. The cartridge was conditioned with hexane, washed to remove nonpolar interferences, and eluted with an acetonitrile/dichloromethane mixture. The eluate was evaporated and reconstituted in methanol.

Instrumentation:

• Liquid chromatography: ACQUITY UPLC H-Class with CORTECS C18, 2.1 × 100 mm, 2.7 µm solid-core column.
• Mobile phases: 0.1% formic acid in water (A) and in methanol (B).
• MS detection: Xevo TQD with electrospray ionization in positive mode, multiple reaction monitoring.

Main Results and Discussion

• Recovery: Most Sudan dyes showed recoveries between 75–100% at 10–100 ppb, except Sudan Orange G (~46–54%) due to stronger silica retention.
• Cleanup efficacy: SPE significantly reduced matrix coloration and concentrated analytes nearly sevenfold.
• Chromatography: The solid-core column delivered sharp peaks and consistent retention times over 200+ injections, with backpressure around 3100 psi—compatible with conventional HPLC systems.
• Sensitivity: Low parts-per-billion detection limits were achieved, enabling reliable screening of trace contaminants.

Benefits and Practical Applications

• Regulatory compliance: Enables routine monitoring of illegal Sudan dyes in food-grade oleoresins.
• Operational flexibility: Method adapts to both HPLC and UPLC platforms without compromising performance.
• Efficient workflow: Simplified SPE cleanup offers high throughput and reproducible sample preparation.

Future Trends and Potential Uses

• UPLC enhancement: Transition to 1.6 µm solid-core columns for faster separations and higher resolution.
• Method expansion: Adaptation to other food matrices and wider classes of colorants or contaminants.
• Automation: Integration of on-line SPE for increased throughput and reduced manual handling.

Conclusion

The described SPE-LC-MS method combining a silica-based cleanup with a CORTECS C18 solid-core column offers a sensitive, robust, and versatile approach for detecting Sudan dyes in chili oleoresin. Its compatibility with existing HPLC infrastructure and capability for rapid, reproducible analysis make it well-suited for food safety and regulatory laboratories.

References

No literature references were provided in the original text.