Quantitative analysis of illegal dyes in eggs using LC/MS/MS

Significance of the Topic

Egg yolk color is a critical quality attribute that influences consumer acceptance and may be artificially enhanced by feeding hens illegal synthetic dyes. Detection of these residues in eggs is essential to ensure food safety and comply with regulatory standards.

Objectives and Study Overview

This study aimed to develop and validate a highly sensitive LC/MS/MS method for simultaneous quantitation of four industrial Sudan dyes (I–IV) and para red in egg yolk. Key goals included achieving low part-per-billion limits of quantitation, high specificity in a complex matrix, and robust repeatability.

Methodology and Instrumentation

Sample preparation combined a QuEChERS extraction protocol with acetonitrile/water, centrifugation at −10 °C, and cleanup using a C18 solid-phase extraction cartridge. Matrix-matched calibration curves (1–100 ppb) were prepared from the cleaned extract.
Chromatographic separation was performed on a Shim-pack XR-C8 column (75 mm×3 mm, 2.2 μm) using a water/acetonitrile gradient with 0.1% formic acid at 0.4 mL/min and 40 °C. The LC system (Nexera UHPLC) was coupled to a Shimadzu LCMS-8040 triple quadrupole mass spectrometer with electrospray ionization. Fast polarity switching and optimized multiple reaction monitoring (MRM) transitions were employed for each dye.

Main Results and Discussion

The method achieved a limit of quantitation of 1 ppb for all five dyes in both aqueous standards and egg yolk extracts. Calibration was linear over 1–100 ppb with correlation coefficients above 0.99. Accuracy ranged from 90% to 110%, and precision (RSD) was below 10%. Background interference was effectively minimized, enabling clear chromatographic separation within a 6-minute run time.

Benefits and Practical Applications

• Enables regulatory laboratories to screen eggs for multiple illegal dyes at trace levels with high confidence.
• Supports quality control in egg production by detecting unauthorized feed additives.
• Matrix-matched calibration ensures reliable quantitation in complex biological samples.

Future Trends and Potential Applications

• Extension of this workflow to other food matrices, such as dairy or meat products.
• Automation and high-throughput adaptations for routine food safety monitoring.
• Integration with high-resolution mass spectrometry for non-targeted screening of emerging contaminants.

Conclusion

The validated LC/MS/MS method provides a rapid, sensitive, and reliable tool for detecting illegal Sudan dyes and para red in egg yolk, reinforcing food safety and regulatory compliance.

Reference

1. Piatkowska M., Jedziniak P., Zmudzki J. Bull Vet Inst Pulawy 58 (2014): 247–253.
2. Dominguez-Alvarez J. et al. J Chromatogr A 1278 (2013): 166–174.