Trace analysis of total fluorine in human blood using combustion ion chromatography for fluorine: A mass balance approach for the determination of known and unknown organofluorine compounds

The number of perfluorochemicals (PFCs) that have been found in biological and environmental matrices is increasing as analytical standards and methods evolve. Perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) constitute only a fraction of the total suite of PFCs found in environmental and biological matrices. A robust method and approach is needed to evaluate the mass of fluorinated compounds in biological matrices. In this study, we developed a method to measure total fluorine (TF) and organic fluorine (TOF) in human blood matrices using combustion ion chromatography (CIC). Blood matrices (whole blood, serum, and plasma) were analyzed in bulk to determine TF. An aliquot of the blood was also extracted with organic solvents such as methyl-tert-butyl ether (MTBE) and hexane, and organic and aqueous extracts were separated, to fractionate organofluorines from inorganic fluorine. The organic layer was analyzed for TF by CIC, and for known PFCs by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). PFCs measured by HPLC-MS/MS accounted for >80% of the TF in the organic fraction. The aqueous fraction contained inorganic fluorine and other non-extractable organofluorines. However, in the bulk sample, fluoride and non-extractable organofluorines accounted for >70% of the TF in blood samples from the general population. In occupationally exposed individuals, known organofluorines accounted for a major proportion of the TF. These results suggest the existence of yet uncharacterized fluorine fraction in human blood. Further studies are needed to characterize the aqueous fraction that contains inorganic fluorine and non-extractable forms of fluorine.