Microplastics Characterization in Carbonated Beverages and Apple Juice by Laser Direct Infrared

Significance of the Topic

Microplastic contamination in food and beverages is an emerging public health and environmental concern. Bottled and packaged drinks such as carbonated beverages and apple juice can introduce microplastic particles into the human diet through packaging materials and processing conditions. Reliable, high-throughput methods are needed to monitor and control microplastic levels in consumer products.

Study Objectives and Overview

This study evaluates a rapid and automated workflow using the Agilent 8700 Laser Direct Infrared (LDIR) chemical imaging system to detect and characterize microplastics in carbonated beverages and apple juice. Samples packaged in polymeric, glass, aluminum, and multilayer carton containers were analyzed directly on aluminum-coated filters with minimal preparation, demonstrating a practical approach for routine surveillance.

Methodology

Sample preparation and quality control procedures were designed to minimize background contamination:

• Degassing of carbonated drinks by slow venting at room temperature for eight hours.
• Vacuum filtration of entire beverage volumes through aluminum-coated polyester membranes (0.8 µm pore size).
• Two-step prefiltration of apple juice using 5 µm polycarbonate filters to prevent clogging, followed by transfer to aluminum-coated membranes via a rinse.
• Procedural blanks (45 mL microplastic-free water) processed alongside samples to establish baseline contamination (mean background: 2 particles per 45 mL, σ = 1.4).

Used Instrumentation

The analytical platform consisted of the Agilent 8700 LDIR system equipped with a Quantum Cascade Laser scanning the mid-infrared fingerprint region (1,800–975 cm⁻¹). Two visible-light cameras and Agilent Clarity software enabled:

• Automated Particle Analysis workflow for rapid particle detection (scan at 1,442 cm⁻¹) and imaging.
• Real-time spectral matching against the Microplastics Starter library.
• Integrated data reporting for particle counts, size distribution, and polymer identification.

Main Results and Discussion

Microplastics were detected in all beverage types, with polyvinyl chloride (PVC) and polyethylene terephthalate (PET) most prevalent:

• Carbonated beverages in rPET bottles, aluminum cans, and glass bottles contained 50, 39, and 384 microplastic particles per sample (HQI > 0.85), respectively. Glass-bottle samples showed unexpectedly high PVC levels, possibly from cap liners or cross-contamination.
• Apple juice in a carton yielded 66 particles (predominantly polyethylene from inner linings) in 200 mL, while the PET bottle sample contained 20 particles in 250 mL (mainly PET).
• Detected particle sizes ranged from 20 µm to >500 µm. Background residue on filters did not impede automated detection or identification.

Benefits and Practical Applications

The direct-on-filter LDIR approach offers:

• Minimal sample preparation without digestion or density separation.
• Reduced risk of contamination and high recovery of particles.
• High throughput with automated imaging and polymer identification.
• Actionable data for quality control in beverage manufacturing and regulatory compliance.

Future Trends and Applications

Advances that can enhance microplastics monitoring include:

• Expansion of spectral libraries to cover diverse polymer additives and weathered particles.
• Integration with automated sample handling for continuous online monitoring.
• Application to a wider range of food matrices and environmental samples.
• Alignment with evolving regulatory standards and exposure assessments.

Conclusion

The Agilent 8700 LDIR chemical imaging system provides a robust, automated platform for rapid detection and characterization of microplastics in carbonated beverages and apple juice. Its direct-on-filter workflow, coupled with reliable quality control and real-time spectral matching, supports efficient routine analysis and contributes to improved understanding and management of microplastic exposure in consumer products.

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