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Establishing performance metrics for quantitative non-targeted analysis: a demonstration using per- and polyfluoroalkyl substances
Citation:
Pu, S., J. McCord, J. Bangma, AND J. Sobus. Establishing performance metrics for quantitative non-targeted analysis: a demonstration using per- and polyfluoroalkyl substances. Analytical and Bioanalytical Chemistry. Springer, New York, NY, 416:1249-1267, (2024). https://doi.org/10.1007/s00216-023-05117-4
Impact/Purpose:
Non-targeted analysis (NTA) is commonly applied for qualitative environmental screening, but can be significantly improved by the development of quantitative applications of NTA data. We examined mixtures of PFAS standards as a test case for the development of quantitative non-targeted analysis (qNTA) approaches and compared them to traditional targeted quantitation approaches. This manuscript contributes to the development of a standardized set of metrics for comparing and optimizing emerging qNTA approaches based on accuracy, uncertainty, and reliability. These metrics were used to evaluate “expert-selected surrogate calibration” and "global surrogate calibration" approaches for estimating PFAS concentrations. Other researchers seeking to develop qNTA approaches can apply the same performance metrics for optimization, and future inclusion of uncertainty estimates of qNTA predictions lays the foundation for their inclusion in a complete risk management workflow for emerging PFAS.
Description:
Non-targeted analysis (NTA) is an increasingly popular technique for characterizing undefined chemical analytes. Generating quantitative NTA (qNTA) concentration estimates requires the use of training data from calibration “surrogates,” which can yield diminished predictive performance relative to targeted analysis. To evaluate performance differences between targeted and qNTA approaches, we defined new metrics that convey predictive accuracy, uncertainty (using 95% inverse confidence intervals), and reliability (the extent to which confidence intervals contain true values). We calculated and examined these newly defined metrics across five quantitative approaches applied to a mixture of 29 per- and polyfluoroalkyl substances (PFAS). The quantitative approaches spanned a traditional targeted design using chemical-specific calibration curves to a generalizable qNTA design using bootstrap-sampled calibration values from “global” chemical surrogates. As expected, the targeted approaches performed best, with major benefits realized from matched calibration curves and internal standard correction. In comparison to the benchmark targeted approach, the most generalizable qNTA approach (using “global” surrogates) showed a decrease in accuracy by a factor of ~4, an increase in uncertainty by a factor of ~1000, and a decrease in reliability by ~5%, on average. Using “expert-selected” surrogates (n = 3) instead of “global” surrogates (n = 25) for qNTA yielded improvements in predictive accuracy (by ~1.5×) and uncertainty (by ~70×) but at the cost of further-reduced reliability (by ~5%). Overall, our results illustrate the utility of qNTA approaches for a subclass of emerging contaminants and present a framework on which to develop new approaches for more complex use cases.
URLs/Downloads:
DOI: Establishing performance metrics for quantitative non-targeted analysis: a demonstration using per- and polyfluoroalkyl substances
https://pubmed.ncbi.nlm.nih.gov/38289355/