Application of a Quantitative Non-targeted Analysis Workflow to Characterize PFAS in Environmental Waters

Non-targeted analysis (NTA) enables the detection of
novel chemicals
but is limited in providing quantitative estimates for risk-based
interpretation. Quantitative NTA (qNTA) using surrogate chemicals
has been previously explored, yielding metrics for qNTA performance
and proof-of-principle approach comparisons across matrices. Here,
we apply that work in an integrated qNTA workflow, with demonstration
on surface and groundwaters impacted by historic PFAS waste. Commercially
available surrogate chemicals (n = 37) spiked into
pooled matrix provided initial calibration data and were used for
qNTA estimation via a naïve bounded response factor approach.
A validation subset, using paired NTA and targeted analysis estimates
(16 PFAS and 129 paired values), showed median accuracy within a factor
of 2, an uncertainty fold-range of 12, and overall reliability of
85%. Lower than expected reliability indicates an underestimation
of uncertainty, likely from suboptimal surrogate selection. The validated
qNTA workflow produced concentration and uncertainty estimates for
210 individual PFAS, with legacy and emerging PFAS estimated concentrations
as high as parts-per-billion. PFAS with available standards (n = 22) contributed, on average, to 91% of the estimated
sum concentrations. These findings suggest quantitative estimation
for chemicals identified via NTA is valuable to ensure that exposure,
hazard, and risk assessments consider the total PFAS burden for impacted
watersheds.