Sulfite determination in beet sugar

Importance of the Topic

Monitoring trace levels of sulfites in beet sugar is critical for ensuring food safety, meeting regulatory requirements, and protecting consumer health. As beet sugar production rises globally, rapid and reliable quantification of naturally occurring sulfite compounds supports quality control and compliance in the sugar industry.

Objectives and Study Overview

This study presents an automated potentiometric titration method for quantifying low concentrations of sulfites in beet sugar crystals. Utilizing the Metrohm OMNIS Professional Titrator and a platinum ring Pt Titrode, the procedure aims to replace labor-intensive iodometric titrations and visual endpoints with a fully automated, instrument-driven workflow.

Methodology and Instrumentation

No sample pretreatment is required beyond weighing. Key steps include:

• Calibration of thiosulfate strength by titrating 0.005 mol/L sodium thiosulfate against 0.005 mol/L potassium dichromate.
• Calibration of iodine concentration by titration of 0.004 mol/L iodine against the standardized thiosulfate solution.
• Analytical titration: Dissolve 50.0 g of beet sugar in 150 mL deionized water, add 5 mL of 1 mol/L HCl, and titrate with the calibrated iodine solution. Endpoint detection is performed potentiometrically using the Pt Titrode on the OMNIS platform.

Main Results and Discussion

Five replicate analyses yielded an average sulfite content of 2.7 mg/L, with an absolute standard deviation of 0.07 mg/L (2.6% relative). The potentiometric titration curve displayed a distinct inflection at the endpoint, confirming the method’s precision and reproducibility. The 30 µL maximum dosing increment prevented overshoot and ensured accurate results.

Benefits and Practical Applications

• Fully automated titration reduces dependence on skilled analysts and subjective visual indicators.
• Enhanced safety and handling through 3S Liquid Adapter technology.
• Accelerated throughput and consistent data quality support routine QA/QC in sugar production facilities.

Future Trends and Potential Applications

• Extension of automated potentiometric methods to other food matrices and beverages containing sulfites.
• Integration with inline process monitoring for real-time quality assurance in sugar refineries.
• Hybrid techniques combining titration with spectroscopic or chromatographic detection for multi-analyte assays.
• Development of miniaturized, portable platforms for field testing.

Conclusion

The Metrohm OMNIS titration system, paired with a Pt Titrode, provides a robust, precise, and user-friendly solution for automated sulfite determination in beet sugar. This approach streamlines analysis, enhances safety, and ensures compliance with food safety standards.

Used Instrumentation

• OMNIS Professional Titrator with magnetic stirrer
• 2 mL OMNIS cylinder unit
• Digital platinum ring Pt Titrode with integrated reference
• OMNIS Stand-Alone software license

References

• U.S. Department of Agriculture. Sugar and Sweeteners – Background. USDA Economic Research Service (accessed 2025-08-20).