Improved selectivity for the analysis of maternal serum and cord serum for polyfluoroalkyl chemicals

Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid, two of the most widely studied polyfluoroalkyl chemicals (PFCs), can cross the placenta. Therefore, data on the exposure to PFCs of the very young are needed to evaluate the potential health effects associated with such exposure. Human serum, especially serum collected from pregnant women and cord serum, may contain endogenous components that can interfere in the separation by high performance liquid chromatography (HPLC) of PFOS and another PFC of interest, perfluorohexane sulfonic acid (PFHxS), from other serum biomolecules. The presence of such interferences may prevent the adequate quantification of PFOS and PFHxS in cord serum or serum collected from pregnant women, and potentially hinder the assessment of gestational exposure to these important PFCs using biomonitoring. We have modified our on-line solid phase extraction-HPLC-isotope dilution-tandem mass spectrometry analytical method for measuring PFCs in serum and developed an approach that allows for the elimination of these potential interferences without compromising analytical sensitivity and throughput. The combination of acetonitrile as the HPLC mobile phase organic solvent and a Betasil C8 HPLC column provided the best separation of PFOS and PFHxS from interferent peaks. In addition to eliminating these interferences, the acetonitrile method has a shorter runtime and is more sensitive for most PFCs (limits of detection were 0.1 ng/mL except for PFOS (0.2 ng/mL)) than our previous method that used methanol for the HPLC separation. The present method should improve the precise and selective analysis of maternal and cord serum for PFCs.