Accurate Microplastic Characterization in Infant Formula

Importance of the Topic

Microplastics are pervasive environmental pollutants found in water, food and consumer products. Infants may be particularly vulnerable to exposure through formula feeding, yet the complex composition of infant formulas—lipids, proteins, minerals and sugars—poses challenges for reliable microplastic extraction and identification. Rigorous analytical workflows are essential to assess exposure risks and support quality control in food safety testing.

Objectives and Study Overview

This study aimed to demonstrate a streamlined, high-throughput method for isolating, identifying and quantifying microplastics in two commercial infant formula brands using the Agilent 8700 Laser Direct Infrared (LDIR) Chemical Imaging System. Key objectives included:

• Developing an effective sample preparation protocol for cream and aqueous fractions of formula
• Validating instrument performance and spectral matching via Clarity software
• Quantifying microplastic loads and polymer types in each formula layer

Methodology and Instrumentation

Sample Preparation:

• Dissolve 5 g of formula in 30 mL saturated NaCl, shake and centrifuge to separate cream (upper) and aqueous (lower) layers
• Digest the cream layer with 0.1 M NaOH at 50–60 °C, then filter both layers through a 14 µm polycarbonate filter and rinse with ethanol
• Transfer particulate residue onto 0.8 µm polyester (PETG) gold-coated filters for analysis

Quality Control:

• Test Milli-Q water, ethanol and NaCl solution by LDIR to detect and remove background microplastics
• Filter reagents repeatedly and maintain glassware under foil to prevent airborne contamination

Instrumentation:

• Agilent 8700 LDIR Chemical Imaging System with Clarity software
• Automated Particle Analysis method using Microplastics Starter 2.0 spectral library
• Scan mode at single wavenumber (1,442 cm⁻¹) for particle detection, followed by sweep mode for full mid-IR spectra

Results and Discussion

Reagent Screening:

• Initial QC revealed six microplastics (PE, PU) in water and 81 particles in NaCl; repeated filtration eliminated contaminants

Formula Analysis:

• Brand A: 4,472 total particles; 97 confirmed microplastics (HQI > 0.8), predominantly PE and PP in both layers, size range 20–100 µm
• Brand B: 1,078 total particles; 22 microplastics identified, mainly PC, PE and PP, all 20–100 µm
• Remaining particles were natural polyamides, cellulose or undefined materials (HQI < 0.8)
• Fiber-shaped contaminants from laboratory textiles were successfully distinguished as cellulosic

The direct on-filter LDIR workflow minimized sample handling, reduced contamination risk and enabled rapid, fully automated spectral matching and quantification.

Practical Benefits and Applications

The described method delivers:

• Fast turnaround without solvent evaporation or manual particle transfer
• High confidence polymer identification using a curated spectral library
• Scalable throughput for routine monitoring in food safety laboratories

Future Trends and Opportunities

Emerging directions include:

• Enhanced sample cleanup via enzymatic or oxidizing digestion to reduce natural matrix interferences
• Expansion of spectral libraries with emerging polymer additives and environmental coatings
• Integration of automated image analytics and machine learning for improved particle classification
• Application to other complex matrices (e.g., dairy, confectionery, processed foods)

Conclusion

The Agilent 8700 LDIR system coupled with Clarity software provides a robust, efficient workflow for microplastic analysis in infant formula. It overcomes matrix complexity through targeted digestion, on-filter analysis and automated spectral matching, delivering accurate polymer identification and quantification with minimal contamination risk. This approach is well suited for high-volume routine testing and supports ongoing efforts to monitor infant exposure to microplastics.

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