LC-MS/MS method development for sulfites in food and beverage

Importance of Sulfite Analysis

Sulfites are widely used as antioxidants and bleaching agents in foods such as dried fruits, juices, and wines. While they protect product quality, sulfite residues can trigger adverse reactions in sensitive individuals. Regulatory agencies, including the US FDA, require labeling for products containing over 10 mg/kg of sulfites. Reliable, rapid quantification methods are therefore essential for quality control, regulatory compliance, and consumer safety.

Objectives and Study Overview

This work aimed to establish a fast, sensitive LC-MS/MS method for total sulfite determination in food and beverage matrices. By adapting the FDA’s recommended approach, the study sought to halve analysis time and expand the calibration range, thus enhancing laboratory throughput and reducing sample dilution steps.

Methodology and Instrumentation

Free sulfite in samples was derivatized to hydroxymethylsulfonate (HMS) via reaction with formaldehyde. Dried fruits underwent homogenization, shaking, sonication, and centrifugation, while wine samples were simply diluted. Cleanup involved C18 solid-phase extraction to remove lipophilic interferences, followed by heating at 80 °C to complete derivatization. Chromatographic separation was achieved using hydrophilic interaction liquid chromatography (HILIC), and detection employed electrospray ionization with multiple reaction monitoring.

Used Instrumentation

• Shimadzu LCMS-8050 triple quadrupole mass spectrometer
• Shimadzu Nexera UHPLC system
• GL Sciences InertSep C18 SPE cartridges (500 mg/6 mL)
• 0.2 μm PTFE syringe filters

Results and Discussion

The calibration curve for HMS remained linear from 0.01 to 20 ppm, eliminating the need for high-level dilutions. The total run time was reduced from 24 minutes to 12 minutes with a 2 μL injection volume. Recovery experiments in dried fruits spiked at 5–10 μg SO₂/g yielded 84.9–99.2% recoveries. Wine samples spiked at 1–10 μg SO₂/g showed recoveries between 95.2% and 104.0%. These performance metrics satisfy international labeling thresholds and demonstrate method robustness.

Practical Implications and Benefits

This streamlined LC-MS/MS protocol offers high throughput, broad dynamic range, and reliable quantification, making it well suited for routine quality assurance in the food and beverage industry. The simplified sample preparation and short analysis time support efficient regulatory testing and enhance laboratory productivity.

Future Trends and Applications

Emerging trends include automation of sample extraction and cleanup, coupling with high-resolution mass spectrometry for improved selectivity, and the development of portable MS platforms for on-site testing. Expanding the method to other sulfur-based additives and allergens could further broaden its applicability.

Conclusion

A rapid UHPLC-MS/MS method was successfully developed for sulfite analysis in diverse food and beverage matrices. The approach achieves a 12-minute runtime, a wide calibration range up to 20 ppm, and high recovery rates, aligning with global regulatory requirements and ensuring consumer safety.

References

• U.S. Food and Drug Administration. Code of Federal Regulations, Title 21, Part 101.100(a)(4). 2018.
• Carlos K. S.; de Jager L. S. Collaborative study on sulfite determination by LC-MS/MS. Journal of AOAC International. 2017;100(6):1785–1794.
• U.S. Food and Drug Administration. Method C-004.03: Determination of Sulfites in Food using LC-MS/MS. 2021.