Iodine monitoring in natural sources

Significance of the topic

Monitoring iodide levels in food matrices is essential due to iodine’s role in thyroid hormone synthesis and neural development, especially in vulnerable populations. Excess or deficient intake can lead to health issues, making reliable analytical methods critical for nutritional assessment and quality control.

Objectives and study overview

This study aims to develop a fast, reproducible procedure for quantifying free iodide in milk samples. By integrating inline dialysis for sample cleanup with ion chromatography and amperometric detection, the method targets enhanced throughput and consistent performance across multiple analyses.

Methodology and sample preparation

Three commercial milk samples were diluted 20-fold with ultrapure water. Automated Low Volume Inline Dialysis removed proteins and macromolecules via a 0.2 µm cellulose acetate membrane, isolating iodide for direct injection into the ion chromatograph with amperometric detection in DC mode. A flexiPAD cleaning cycle was programmed to regenerate the working electrode after each run, preventing fouling.

Used Instrumentation

• 930 Compact IC Flex with Low Volume Inline Dialysis accessory
• Ag/AgCl reference and silver thin-layer working electrode cell
• 858 Professional Sample Processor – Pump with two-channel peristaltic pump
• Metrosep A Supp 17 – 150/4.0 separation column

Key results and discussion

Natural iodide concentrations ranged from below the limit of detection to 141 µg/L. Spiking experiments (50–200 µg/L) yielded recoveries between 94 % and 107 %, demonstrating accuracy and method linearity. The limit of detection was determined as 27 µg/L (DIN 32645) and 36 µg/L (signal-to-noise), meeting regulatory requirements for trace analysis.

Benefits and practical applications

The automated inline dialysis streamlines sample preparation, reducing manual labor and error. Continuous electrode cleaning ensures stable amperometric signals over extended runs, improving reproducibility. The method supports high-throughput monitoring of iodide in dairy products for nutritional labeling, regulatory compliance, and research studies.

Future trends and potential applications

Advancements may include coupling with mass spectrometric detection for speciation studies, miniaturized inline dialysis modules for field deployment, and application to other complex food or environmental matrices. Integration with laboratory information management systems can further enhance data handling and traceability.

Conclusion

The presented IC-amperometry approach with automated inline dialysis provides a robust, fast, and sensitive protocol for iodide measurement in milk. High recoveries, low detection limits, and automated maintenance render it a practical solution for routine analysis.

References

• Sakai N; Esho OY; Mukai M. Iodine Concentrations in Conventional and Organic Milk in the Northeastern U.S. Dairy 2022, 3(2), 211–219.
• van der Reijden OL; Zimmermann MB; Galetti VI. Iodine in Dairy Milk: Sources, Concentrations and Importance to Human Health. Best Pract Res Clin Endocrinol Metab 2017, 31(4), 385–395.
• Gunnarsdottir I; Dahl LI. Iodine Intake in Human Nutrition: A Systematic Literature Review. Food & Nutrition Research 2012.