Challenges in PFAS Postdegradation Analysis: Insights from the PFAS-CTAB Model System

Area of Science:

• Environmental Chemistry
• Analytical Chemistry

Background:

• Per- and polyfluoroalkyl substances (PFAS) are persistent synthetic chemicals with widespread use.
• PFAS degradation yields complex mixtures, posing analytical challenges.
• Interactions like ion pairing and micelle formation affect PFAS measurements.

Purpose of the Study:

• To investigate the impact of cetyltrimethylammonium bromide (CTAB) on PFAS analytical methods.
• To evaluate the accuracy of standard EPA methods for post-degradation PFAS analysis in the presence of CTAB.

Main Methods:

• Addition of ppb-level CTAB to PFAS mixtures.
• Analysis using EPA Methods 537.1, 533, and 1633.
• Evaluation of calibration curve linearity, sensitivity, reproducibility, and matrix effects.

Main Results:

• CTAB severely compromises PFAS calibration curve linearity, sensitivity, and reproducibility.
• Standard EPA methods showed poor PFAS recovery in CTAB mixtures, with significant matrix effects.
• Method 1633 demonstrated the lowest CTAB interference among tested methods.

Conclusions:

• CTAB addition significantly impacts PFAS quantification, even with internal standards.
• Method 1633 is the most suitable for post-degradation PFAS analysis among the evaluated methods.
• Systematic evaluation of matrix effects using recovery matrices is recommended for future PFAS degradation studies.