Trace metals analysis in baby food using inductively coupled plasma mass spectrometry (ICP-MS)

Significance of the Topic

Ensuring the safety and nutritional quality of baby foods is critical because infants are uniquely vulnerable to toxic heavy metals while also requiring adequate essential minerals for healthy growth. Regulatory agencies worldwide mandate strict limits for arsenic, lead, cadmium and mercury in final products, and routine, reliable analysis is needed to confirm compliance and protect child health.

Objectives and Study Overview

This application note describes a complete workflow for quantitative determination of toxic and essential elements in diverse baby food matrices. The goals were to develop an automated, reproducible sample preparation method and a sensitive, interference-free analytical protocol using triple-quadrupole ICP-MS, capable of meeting regulatory limits while maintaining high throughput.

Instrument and Experimental Setup

Sample digestion used a Milestone UltraWAVE microwave system with patented Single Reaction Chamber technology. Dry or fatty samples (0.5 g) and wet samples (1.0 g) were digested with 2 mL HNO₃ and 0.5 mL HCl, then brought to 50 mL. Digests were analyzed on a Thermo Scientific iCAP MTX ICP-MS coupled to an iSC-65 autosampler. Argon gas dilution (approximately 5×) was applied inline to accommodate varied matrices without additional dilution. The ICP-MS alternated between single-quadrupole KED mode and triple-quadrupole O₂ reaction mode to suppress polyatomic, isobaric and doubly charged interferences. Internal standards (Sc, Ge, Rh, Ir) compensated for matrix effects.

Analytical Methodology

A multielement calibration (0.1–100 µg/L for trace elements; up to 50 mg/L for nutrients) and two quality control levels were prepared. Limits of quantification for arsenic, cadmium, mercury and lead in final baby food ranged from 0.2 to 0.8 µg/kg, comfortably below regulatory maxima. QC checks every ten samples demonstrated recoveries within ±20% for all elements.

Main Results and Discussion

Certified reference materials (skimmed milk powder, infant cereal, sweet digestive biscuit) yielded recoveries of 95–115% for As, Cd, Hg and Pb, confirming accuracy. Internal-standard responses remained within 60–120% over eight-hour sequences. Analysis of six commercial baby foods revealed that a salmon-vegetable puree exceeded the 10 µg/kg limit for total arsenic (23 µg/kg) and slightly exceeded the 2 µg/kg mercury limit, reflecting known bioaccumulation in fish. Three products surpassed the 5 µg/kg cadmium limit, and one vegetable puree was above the 5 µg/kg lead threshold. Organic arsenic likely predominates in fish; confirming speciation would require IC-ICP-MS.

Benefits and Practical Applications

• The combined microwave digestion and triple-quadrupole ICP-MS approach delivers robust, high-throughput screening across diverse baby food matrices without manual dilution adjustments.
• Inline argon dilution and automated acid dispensing streamline workflow, reduce operator error, and support consistent quantification at or below regulatory limits.
• Effective interference elimination via KED and O₂ reaction modes ensures reliable trace-level detection of toxic and essential elements in a single run.

Future Trends and Application Opportunities

Advancements may include coupling ion chromatography for arsenic speciation, expanding to other contaminant classes (e.g., mycotoxins), and integrating real-time data analytics for in-line process control. Miniaturized sample preparation and automated robotics could further boost throughput in quality-control laboratories.

Conclusion

This workflow meets stringent regulatory requirements for toxic element analysis in baby foods, providing accurate, reproducible results across varied sample types. Its robustness, sensitivity, and automation capabilities make it well suited for routine safety testing in high-productivity lab environments.

References

1. Nóbrega J.A., Carnaroglio D. Best practices in sample preparation of baby food for trace metal determination. Milestone Srl.; 2022.
2. Sengupta S., Surekar B., Kutscher D. Using triple quadrupole ICP-MS to improve speed, sensitivity and accuracy of toxic and nutritional elements analysis in baby foods. Thermo Fisher Scientific Application Note 000209; 2021.
3. Raab A., McSheehy Ducos S. Determination of inorganic arsenic in rice using IC-ICP-MS. Thermo Fisher Scientific Application Note 43255; 2018.