Preserved and Accessible: Quantifying PFAS in Formalin-Fixed and Paraffin-Embedded Tissues for Retrospective Exposure...

Area of Science:

• Environmental Chemistry
• Toxicology
• Analytical Chemistry

Background:

• Formalin-fixed tissues are an underutilized resource for historical chemical exposure reconstruction.
• Per- and polyfluoroalkyl substances (PFAS) are persistent contaminants requiring robust biomonitoring methods.
• Fixation and embedding processes may impact analyte stability and quantification accuracy.

Purpose of the Study:

• To develop and validate a liquid chromatography-electrospray tandem mass spectrometry (LC-ESI-MS/MS) method for quantifying six PFAS in various mouse tissues.
• To assess the impact of formalin fixation and paraffin embedding on PFAS recovery and stability.
• To provide insights into compound- and matrix-specific recovery patterns for retrospective PFAS analysis.

Main Methods:

• Developed an LC-ESI-MS/MS method to quantify six target PFAS (PFHxS, PFOA, PFOS, PFNA, PFDA, PFUnA).
• Analyzed matched sets of flash-frozen, formalin-fixed, and formalin-fixed paraffin-embedded mouse tissues (liver, kidney, ileum, brain).
• Tracked PFAS recovery and loss through fixation, storage, and deparaffinization steps.

Main Results:

• Mean sum of PFAS in fresh tissues ranged from 279.2 ng/g (brain) to 22,628.4 ng/g (liver).
• Formalin fixation yielded 76.7-83.8% PFAS recovery, with 12.6-19.9% in formalin solution.
• Paraffin embedding resulted in 57.4-75.1% recovery, with additional losses during processing. Longer-chain PFAS and higher-burden tissues showed better retention.

Conclusions:

• Quantification of PFAS in archived formalin-fixed and paraffin-embedded tissues is feasible.
• Systematic data on compound- and matrix-specific PFAS recovery patterns are provided.
• Further validation is needed for short/ultrashort PFAS, and correction factors may be required for human tissues with low PFAS loads.