Analysis of 4-Methylimidazole in Caramel Color and Study of High-Speed Analysis

Importance of the Topic

4-methylimidazole is a process byproduct formed during caramel coloring production and has been classified as a carcinogenic hazard by IARC, prompting regulatory limits. It is essential to accurately quantify trace levels of 4-MEI in food and beverage matrices to ensure compliance and consumer safety.

Objectives and Overview

This study develops and compares a conventional HPLC method and a high-speed UHPLC method using the Shimadzu Nexera-i MT for quantifying 4-MEI in cola samples. Key aims include:

• Achieve interference-free separation of 4-MEI in complex matrices.
• Establish calibration linearity down to 50 µg/L.
• Demonstrate rapid analysis through method transfer to the UHPLC flow line.

Methodology and Instrumentation

Instrumentation used:

• Shimadzu Nexera-i MT with both HPLC and UHPLC flow lines

General HPLC conditions:

• Column: Shim-pack™ VP-ODS (250 mm × 4.6 mm, 5 µm)
• Mobile phase: Methanol (A) and water containing 25 mmol/L phosphate buffer (pH 2.8) and 25 mmol/L sodium 1-octanesulfonate (B) at a 1/9 ratio
• Flow rate: 1 mL/min; Column temperature: 40 °C; Injection volume: 20 µL; Detection: PDA at 214 nm

High-speed UHPLC conditions via method transfer:

• Column: Shim-pack XR-ODS II (100 mm × 3 mm, 2.2 µm)
• Injection volume: 5 µL; other parameters unchanged

Main Results and Discussion

The HPLC method provided clear 4-MEI peaks in spiked cola (50 µg/L) without matrix interference. Calibration from 50 µg/L to 5 mg/L yielded R2>0.9999, repeatability of 3.61% RSD, and spike recovery of 106.8%. The UHPLC approach shortened the run time from 50 minutes to 10 minutes while maintaining linearity (R2>0.9999), reproducibility (2.41% RSD), and recovery (106.8%).

Benefits and Practical Applications

• Accurate trace-level quantification for regulatory compliance.
• Enhanced laboratory throughput through accelerated analysis.
• Flexibility of a single instrument to support both standard and high-speed methods.

Future Trends and Applications

Potential developments include:

• Automated method transfer and dynamic optimization.
• Microflow and miniaturized columns to reduce solvent usage.
• Integration with high-resolution mass spectrometry for confirmatory analysis.

Conclusion

The Shimadzu Nexera-i MT effectively quantifies 4-MEI in caramel-containing beverages using both HPLC and UHPLC modes. Method transfer enables significant time savings without compromising performance, benefiting quality control and compliance.

References

1. IARC Monographs on the Identification of Carcinogenic Hazards to Humans, Vol. 101
2. California Proposition 65 List