Surface-Enhanced Raman Spectroscopy Detection of Per- and Polyfluoroalkyl Substances in Aqueous Film-Forming Foams

Area of Science:

• Analytical Chemistry
• Environmental Science
• Materials Science

Background:

• Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants requiring sensitive detection methods.
• Conventional PFAS detection methods are often costly and not easily scalable for rapid, portable analysis.
• Accurate identification of PFAS is crucial for environmental monitoring, water treatment, and hazard assessment.

Purpose of the Study:

• To develop a rapid and portable method for detecting and identifying specific per- and polyfluoroalkyl substances (PFAS) in complex mixtures.
• To utilize concave cubic gold nanoparticles with surface-enhanced Raman spectroscopy (SERS) for PFAS analysis.
• To differentiate between various regulated PFAS and common fluorinated pharmaceuticals.

Main Methods:

• Concave cubic gold nanoparticles were synthesized and employed for surface-enhanced Raman spectroscopy (SERS).
• SERS was used to detect and differentiate six regulated PFAS (PFHpA, PFNA, PFDA, PFOA, PFHxS, and PFOS) at parts per million concentrations.
• Calculated Raman spectra, solid-state Raman spectra, and 19F NMR were used to elucidate PFAS physicochemical properties.
• Quantitative analysis of PFOA and PFOS was performed, and differentiation of perfluoroalkyl carboxylic acids (PFCA) based on backbone length was achieved.

Main Results:

• The SERS method successfully detected and differentiated six regulated PFAS at concentrations as low as 0.1 ppm for PFOA and PFOS.
• The technique distinguished PFAS from common fluorinated pharmaceuticals.
• Perfluoroalkyl carboxylic acids (PFCA) were differentiated based on their perfluoroalkyl backbone length (C7 to C10).
• SERS analysis successfully identified PFAS in real-world aqueous film-forming foams (AFFFs), validated by mass spectrometry.

Conclusions:

• Concave cubic gold nanoparticle-based SERS provides a viable, cost-effective, and portable approach for PFAS detection and identification.
• This method advances the capability for real-time environmental monitoring and analysis of PFAS in complex samples.
• The findings support the application of SERS in hazardous waste cleanup and workplace hazard identification.