Rapid, Large-Area, Analysis of Microplastics from Plastic Bottles Using Laser Direct Infrared Imaging

Significance of the Topic

Microplastics smaller than 5 mm have become ubiquitous in natural habitats and drinking water, raising concerns about ecological impact and human exposure. Rapid, accurate identification of polymer type, size, and abundance is critical for reliable environmental monitoring.

Study Objectives and Overview

This work demonstrates the use of the Agilent 8700 LDIR chemical imaging system for fully automated detection and identification of PET microplastics. Two preparation methods were tested: direct analysis on infrared reflective slides and on gold-coated filters. The goal was to compare identification accuracy, processing time, and operational simplicity.

Methodology and Instrumentation

Sample Preparation

• Grinding of PET bottle fragments and suspension in ethanol
• Deposition of aliquots on infrared reflective slides and vacuum filtration onto gold-coated polyester filters

Instrumentation Used

• Agilent 8700 LDIR system with tunable quantum cascade laser covering 1800 to 900 cm-1
• Agilent Clarity software for automated Particle Analysis workflow
• Gold-coated membrane filters 0.8 µm pore size and IR reflective glass slides
• JAVAC vacuum pump with regulated pressure for gentle filtration

Key Results and Discussion

Direct slide analysis detected 7949 particles 10–486 µm in diameter, with 95.2% correctly identified as PET and the remainder as trace polymers. Filter analysis revealed 4384 particles 11–413 µm with 99.2% PET accuracy in the first filter and 5411 particles with 98.4% accuracy in the second. Most identifications achieved a hit quality index above 0.8, confirming high confidence even for particles as small as 10 µm.

Benefits and Practical Applications

The LDIR method delivers:

• Large area imaging and rapid raster scanning for high sample throughput
• Minimal sample handling for reduced contamination risk
• Automated particle detection, classification, and reporting without specialized spectroscopy expertise
• Time savings compared to FTIR and Raman microscopy

This approach is well suited to routine environmental testing, quality control in water treatment, and research on microplastic distribution.

Future Trends and Possibilities

Advancements may include expanded polymer libraries for broader identification, integration of machine learning for automated classification, field deployable LDIR modules, and improved sample preparation for nanoplastic detection. Combining LDIR imaging with complementary techniques could yield deeper insights into polymer additive analysis and weathering effects.

Conclusion

The Agilent 8700 LDIR system offers a rapid, accurate, and user-friendly solution for microplastics analysis. Its high-throughput capabilities, coupled with automated workflows and minimal training requirements, make it ideal for routine environmental monitoring and research applications.

References

1. XiaoZhi L Microplastics Are Everywhere but Are They Harmful Nature 2021
2. Schymanski D et al Analysis of Microplastics in Drinking Water Anal Bioanal Chem 413 5969–5994 2021
3. Danence L et al Quick Easy Characterization of Microplastics in Surface Water Agilent Publ 5994-3932EN