Simultaneous Iodine and Bromine Speciation Analysis of Infant Formula by HPLC-ICP-MS

Importance of the Topic

Infant formulas are a primary source of nutrition for many babies and young children, making strict monitoring of micronutrients essential for healthy development. Iodine speciation is critical because iodide offers higher bioavailability than iodate, directly impacting thyroid function. Bromine species differ dramatically in toxicity, with bromate classified as a potential carcinogen while bromide poses lower risks. Rapid, accurate determination of these halogen species supports regulatory compliance and safeguards infant health.

Objectives and Study Overview

This study aimed to establish a fast and reliable method for simultaneous quantification of iodide, iodate, bromide, and bromate in milk-based infant formulas. By coupling high-performance liquid chromatography (HPLC) with inductively coupled plasma-triple quadrupole mass spectrometry (ICP-QQQ), the goal was to achieve baseline separation of all four species within 6.5 minutes and detect sub-ppb concentrations in commercial samples and standard reference material.

Methodology and Instrumentation Used

• Sample Preparation: Two approaches were applied. For speciation, ~0.2 g of powdered formula was extracted in water at 50 °C for 1 h and filtered. For total element analysis, samples were digested in 65% HNO₃ via microwave digestion and diluted.
• Chromatography: An Agilent 1260 Infinity II LC system with a polyhydroxymethacrylate anion exchange column was employed. The mobile phase consisted of 5 mM NaH₂PO₄, 15 mM Na₂SO₄ and 5 mM EDTA at pH 7.0, with a 1.0 mL/min flow and 100 µL injections.
• Detection: An Agilent 8900 ICP-QQQ in single-quad mode with helium cell gas detected ^127I and ^79Br. Key ICP-QQQ settings included a nebulizer gas flow of 1.10 L/min, spray chamber at 2 °C, mass integration time of 0.5 s, and cell gas flow of 2.0 mL/min.

Main Results and Discussion

• Detection Limits: Signal-to-noise limits ranged from 0.072 to 0.667 ppb for all four species.
• Calibration: Linear response (R² ≥ 0.9999) was observed from 0 to 100 ppb.
• SRM Validation: NIST 1849a recoveries for total iodine and iodide were 103% and 101%, respectively; no bromine certification was available.
• Commercial Sample Analysis: Four powdered formulas (two from the USA, two from China) contained only iodide and bromide. Total iodine levels (25.9–54.5 µg/100 kcal) met US and Chinese standards; some exceeded the EU upper limit of 29 µg/100 kcal.
• Spike Recovery: Fortification at 20 and 40 ppb yielded recoveries between 96% and 100%, demonstrating method accuracy and repeatability over multiple injections.

Benefits and Practical Applications

The proposed HPLC-ICP-QQQ approach provides rapid, high-throughput speciation of essential and potentially harmful halogens in infant formulas. It facilitates routine quality control in research, regulatory, and manufacturing laboratories. Its adaptable configuration also permits monitoring of other elemental species in diverse food matrices.

Future Trends and Applications

• Extension to Additional Halogen and Trace Element Species in Foods.
• Automation of Sample Handling for Increased Throughput and Reproducibility.
• Integration with Online Sample Preparation for Real-Time Process Monitoring.
• Application to Other Complex Food and Environmental Matrices.

Conclusion

A concise and robust HPLC-ICP-QQQ method successfully separated and quantified iodide, iodate, bromide, and bromate in infant formulas within 6.5 minutes, with sub-ppb detection limits. The approach demonstrated excellent accuracy and precision in both standard reference materials and commercial products, offering a valuable tool for ensuring the nutritional quality and safety of infant nutrition products.

References

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3. WHO, IARC. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. 2018.
4. Food and Drug Administration. Title 21 CFR Part 107: Infant Formula. 2015.
5. European Commission. Delegated Regulation (EU) 2016/127. Off J Eur Union. 2015;L25:1–29.
6. Ministry of Health of the People’s Republic of China. GB 10765-2010: National Food Safety Standard Infant Formula. 2010.
7. AOAC International. SMPR 2015.006: Arsenic Species Quantitation in Foods and Beverages. 2015.
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