A quantitative framework for optimization, interpretation, and quality control of the PFAS total oxidizable precursor...

Area of Science:

• Environmental Chemistry
• Analytical Chemistry

Background:

• The Total Oxidizable Precursor (TOP) assay estimates per- and polyfluoroalkyl substances (PFAS) precursors.
• Current TOP assay methods lack consistent conditions and quality control, hindering reliability and comparability.

Purpose of the Study:

• To develop a quantitative framework for improving TOP assay performance.
• To enhance the analytical reliability and interlaboratory comparability of PFAS precursor assessment.

Main Methods:

• Systematic optimization of reagent concentrations (persulfate and sodium hydroxide) and their ratios.
• Development of a precursor-product conversion mapping matrix for 27 PFAS precursors and 19 oxidation products.
• Introduction of a conversion-based quality control approach using post-oxidation spiked recovery.

Main Results:

• Oxidation efficiency was best described by the reagent concentration ratio, with optimal performance at a [K2S2O8]/[NaOH] ratio around 0.2.
• A molar conversion yield matrix was established under optimized conditions.
• The proposed quality control method demonstrated feasible post-oxidation spiked recoveries of 70-140% in aqueous samples.

Conclusions:

• The developed framework significantly improves the robustness, reproducibility, and interpretability of the TOP assay.
• This work provides a practical basis for more standardized assessment of PFAS precursors.
• The new quality control approach allows direct assessment of oxidation efficiency within routine LC-MS workflows.