Analysis of Toxic Chemical Substances Adsorbed on Microplastics

Adsorption of Toxic PAHs and PFAS on Microplastics: Quantitative Analysis by GC-MS/MS and LC-MS/MS

Importance of the Topic

Microplastics are ubiquitous carriers of hydrophobic pollutants in aquatic environments. Understanding how toxic polycyclic aromatic hydrocarbons and per- and polyfluoroalkyl substances interact with these particles is essential for assessing ecological and health risks.

Objectives and Study Overview

• Evaluate adsorption of representative PAHs and PFAS on three common microplastic polymers (PP, PS, PE) in water
• Quantify the amount of pollutants adsorbed under controlled laboratory conditions
• Correlate adsorption behavior with pollutant hydrophobicity to infer mechanisms

Methodology and Instrumentation

The study used commercially available polypropylene, polystyrene, and polyethylene particles (<5 mm) immersed in 300 mL ultrapure water spiked with 100 ng PAHs or 8 ng PFAS. Samples were stirred gently for 24 h.
Extraction and Analysis:

• Hexane ultrasonic extraction for PAHs
• Methanol ultrasonic extraction for PFAS
• GCMS-TQ8040 triple quadrupole GC-MS/MS
• LCMS-8060 triple quadrupole LC-MS/MS with Nexera X2
• Stereoscopic microscope STZ-171-TP with Moticam 1080 camera
• Custom adsorption test setup with stainless steel mesh and stirrer

Key Results and Discussion

• All PAH compounds showed measurable adsorption; PFAS adsorption varied by compound
• Polypropylene and polyethylene exhibited higher affinity for PAHs than polystyrene
• Adsorption of PFAS was compound-specific, reflecting structural factors
• Adsorption correlated strongly with hydrophobicity (Log Kow for PAHs, Log D for PFAS), independent of polymer type

Benefits and Practical Applications

• Provides a robust workflow for quantifying pollutant adsorption on microplastics
• Informs environmental monitoring and risk assessment of microplastic-associated contaminants
• Supports regulatory frameworks by profiling pollutant–polymer interactions
• Enables targeted mitigation strategies in water treatment and pollution control

Future Trends and Opportunities

• Expand to emerging flame retardants, pharmaceuticals, and nanoparticles
• Simulate dynamic environmental conditions (pH, salinity, temperature)
• Develop high-throughput screening platforms for broader polymer libraries
• Integrate field sampling with laboratory adsorption assays for real-world validation
• Advance mass spectrometry sensitivity for ultra-trace pollutant detection

Conclusion

The quantitative evaluation of PAH and PFAS adsorption on microplastics by GC-MS/MS and LC-MS/MS revealed distinct polymer-dependent behaviors governed by pollutant hydrophobicity. This methodology offers valuable insights for environmental risk assessments and guides future investigations into pollutant fate on microplastics.

References

• Makoto Yasojima et al. Adsorption Characteristics of Chemical Substances on Microplastics. Proceedings of the 22nd Symposium of the Japan Society on Water Environment (2019).
• Makoto Yasojima et al. Existence of Unknown Chemical Substances Adsorbed on Microplastics Immersed in Rivers and Adsorption Characteristics of Chemical Substances on Microplastics. Proceedings of the 56th Environmental Engineering Research Forum (2019).