Comprehensive evaluation of the analytical efficiency of combustion ion chromatography for per- and polyfluoroalkyl substances in biological and environmental matrices

Combustion ion chromatography (CIC) has emerged as a highly valuable tool in the analysis of per- and polyfluoroalkyl substances (PFAS) in biological and environmental samples, to determine total fluorine content. The information from CIC complements results from targeted analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and indicates the presence of many other organofluorine compounds that remain unaccounted for by the latter technique. However, the effect of different matrices and PFAS types on combustion efficiency has not been systematically evaluated, such as varying chain lengths and head groups, different combustion times, and different types of matrices. Comparison of PFAS with chain lengths of C4 to C12 using equal fluorine equivalents of 5.27 nmol (100 ng) demonstrated no significant differences in the CIC responses, indicating uniform combustion. Further, no significant differences in signal were observed between combustion times ranging from 7.5 to 15 min. However, fluorotelomer alcohols (FTOHs) exhibited losses due to volatility, which could be mitigated using activated carbon, improving intensities by 200-1400%. Variations in matrix exhibited no observable changes in PFAS combustion efficiency for all chain lengths in water, blood, and biosolid matrix. To validate further, CIC was applied in the analysis of real blood and biosolid samples to compare the total fluorine concentrations observed with the concentrations determined by LC-MS/MS. The results of this study highlight the strengths and limitations of CIC as an important complementary method for PFAS analysis for different matrices and provide guidance for optimizing conditions for specific applications and for proper interpretation of CIC results.