Robust multiparameter analysis of infant and follow-on formulas with ion chromatography (IC)

Significance of the topic

The nutritional composition and safety of infant and follow-on formulas are critically regulated worldwide to ensure optimal growth and development in early life. Reliable, multi-parameter analytical methods are essential for manufacturers, regulatory bodies, and testing laboratories to verify compliance with Codex Alimentarius, EU regulations, and national standards, covering nutrients, supplements, and contaminants.

Objectives and study overview

This white paper demonstrates how ion chromatography (IC), combined with advanced sample preparation and detection techniques, can efficiently quantify key carbohydrates, micronutrients, and potential contaminants in infant, toddler, and baby food matrices. It reviews method validation according to ISO, AOAC, and other regulatory norms and highlights robustness, sensitivity, and automation gains.

Methodology and instrumentation

Key analytical workflows employ Metrohm IC systems configured with:

• Specialized separation columns: Metrosep Carb 2 for mono-, di-, and oligosaccharides; Metrosep C4 and C6 for cations and choline; Metrosep A Supp 5/7/17 for anions.
• Detection modes: pulsed amperometric detection (PAD), conductivity detection after suppression, and UV/VIS detection.
• Automation modules: Inline Dialysis and Inline Dilution for sample cleanup and matrix removal; 930 Compact IC and 941 Eluent Production Module for unattended operation; cooled sample storage for stability.
• Sample preparation: Carrez precipitation, acid or enzymatic hydrolysis, solid-phase extraction, and high-pressure or Dose-in gradients for complex matrices.

Main results and discussion

IC methods achieved full compliance with international standards:

• Monosaccharides and lactose profiled by ISO 22184/IDF 244 with PAD, demonstrating detection limits down to 0.5 µg/mL and precise separation via gradient elution.
• Total galacto-oligosaccharides (GOS) quantified under AOAC 2001.02, including fingerprint analysis using PAD and customized gradients.
• Fructan determination validated as AOAC 2016.14 in multi-laboratory trials, delivering accurate totals across 0.03–5 g/100 g in powders.
• Choline measured by non-suppressed conductivity per AOAC 2012.20, with linearity from 1–50 mg/L, LOD 0.34 mg/100 g, and spike recoveries of 92–106%.
• Nitrite and nitrate resolved on Metrosep A Supp 5 columns with LODs at 0.01 mg/kg, meeting health-based ADIs and requiring minimal sample prep.
• Melamine detected in problematic milk powders down to 0.067 mg/kg via IC–UV/VIS, with high-low calibration ensuring accuracy across 0.02–150 mg/L.

Benefits and practical applications of the method

Ion chromatography offers laboratories a unified, cost-effective platform for nutrient and contaminant analysis. Its advantages include:

• High specificity and sensitivity without extensive consumables or labor.
• Seamless method translation across diverse analyte classes.
• Scalability: from pilot-scale R&D to high-throughput QC.
• Full compliance with ISO, AOAC, EU, and Codex requirements.
• Reduced manual steps via inline preparation, lowering error rates and turnaround time.

Future trends and potential applications

Advancements will focus on expanding IC hyphenation (e.g., IC-MS, TitrIC flex) to cover vitamins, amino acids, and emerging contaminants. Laboratory digitalization, real-time monitoring, and integration with data management systems will further streamline regulatory compliance and predictive QC in infant formula production.

Conclusion

Ion chromatography, with dedicated columns, detection modes, and automation strategies, stands as a robust, flexible solution for multi-parameter analysis of infant and follow-on formulas. It enables comprehensive quality control that aligns with stringent global regulations while optimizing laboratory efficiency.

Instrumentation

• Metrohm 930 Compact IC Flex and 940 Professional IC Flex systems
• Metrosep Carb 2 (150/250 mm), C4 150/250 mm, C6 150 mm, A Supp 5/7/17 columns with matching guards
• Detection: PAD (thin-layer Au electrode), non-suppressed/suppressed conductivity, UV/VIS (240 nm)
• Automation: Inline Dialysis, Inline Dilution, 941 Eluent Production Module, sample cooler

References

1. EFSA. Scientific Opinion on the essential composition of infant and follow-on formulae. EFSA J. 2014, 12(7), 3760.
2. Kappes, S.; Zierfels, G. Chromatogr. Today 2016, May/June, 20–22.
3. Brunt, K.; Sanders, P.; Ernste-Nota, V., et al. J. AOAC Int. 2021, 104(3), 732–756.
4. Spichtig, V.; Austin, S.; Brunt, K., et al. J. AOAC Int. 2020, 103(5), 1301–1317.
5. Haselberger, P.; Jacobs, W. A. J. AOAC Int. 2016, 99(6), 1576–1588.
6. Thompson, L. B.; Schimpf, K.; Baugh, S. J. AOAC Int. 2013, 96(6), 1407–1413.
7. Ahmad, S.; Guo, M. R. In Human Milk Biochemistry and Infant Formula Manufacturing Technology, 2nd ed.; Guo, M., Ed.; Woodhead Publishing, 2021.
8. U.S. Food and Drug Administration. Melamine. 2021.