Analysis of Artificial Food Dyes Using UltraPerformance Liquid Chromatography and an Extended Wavelength Photo Diode Array Detector

Significance of the Topic

Artificial synthetic dyes are widely used to enhance the color of food and beverage products. Regulatory limits vary globally, requiring accurate quantification methods to ensure consumer safety and compliance.

Study Objectives and Overview

This application note demonstrates the development of a rapid, ten-minute UltraPerformance Liquid Chromatography (UPLC) method coupled with an extended wavelength Photo Diode Array (PDA) detector for simultaneous analysis of fifteen artificial food dyes and selected isomers in diverse food matrices.

Methodology and Instrumentation

Sample Preparation:

• Powders and candies dissolved in water and centrifuged as needed
• Jam extracted with water and sonication
• Smoked salmon homogenized and extracted with an ethanol:ammonia:water mixture

Chromatographic Conditions:

• Column: ACQUITY UPLC BEH C18 (1.7 µm, 2.1 x 100 mm)
• Mobile phase A: 10 mM ammonium acetate in water
• Mobile phase B: Methanol
• Mobile phase C: Acetonitrile
• Gradient program: initial 97:2:1 A:B:C, ramp to 50:25:25 over 7.4 min, then 2:49:49, re-equilibration to 97:2:1
• Flow rate: 0.45 mL/min; Injection volume: 10 µL; Run time: 10 min

Detector Configuration:

• ACQUITY UPLC PDA eλ Detector
• Wavelength range: 210–700 nm; Extracted channels: 400, 500, 630 nm
• Resolution: 3.6 nm; Sampling rate: 20 points/sec

Main Results and Discussion

The method achieved baseline separation of fifteen dyes with excellent linearity over 0.5–10 000 ppb (R² > 0.999). Calibration for Green S and Allura Red demonstrated consistent response across 4.5 orders of magnitude. Selectivity was enhanced by extracting specific visible wavelengths, effectively removing matrix interferences in iced tea drink mixes, peach-mango powders, and smoked salmon. Repeatability was confirmed by spiking 100 ng/mL carmoisine into orange hard candy, yielding retention time RSD of 0.05% and average recovery of 101.1% over twenty injections.

Benefits and Practical Applications

• Rapid analysis reduces run time and solvent consumption
• Simultaneous quantification of multiple dyes improves laboratory throughput
• Extended wavelength PDA detection offers enhanced selectivity in complex matrices
• Robust performance supports regulatory compliance across diverse food products

Future Trends and Potential Applications

Anticipated advancements include integration of UPLC-PDA with mass spectrometry for confirmatory analysis, development of in-line process monitoring for real-time quality control, and expansion of the detectable wavelength range up to 800 nm to accommodate emerging color additives.

Conclusion

The described UPLC-PDA eλ method provides a fast, sensitive, and robust platform for the simultaneous analysis of artificial food dyes in various food and beverage matrices, meeting regulatory requirements while maximizing laboratory efficiency.

Reference

1. US e-CFR Title 21, Chapter I, Subchapter A, Part 74, Subpart A – Foods.
2. Stevens L. J. et al., Clin Pediatr, 2014.
3. Zou T. et al., Food Chem, 2013; 138:1742–1748.