Blood Plasma Sample Preparation Method for the Assessment of Thyroid Hormone-Disrupting Potency in Effect-Directed Analysis

A sample preparation method combining solid-phase extraction (SPE) and liquid-liquid extraction (LLE) was developed to be used in Effect-Directed Analysis (EDA) of blood plasma. Until now such a method was not available. It can be used for extraction of a broad range of thyroid hormone (TH)-disruptors from plasma with high recoveries. Validation of the method using spiked cow plasma showed good recoveries for hydroxylated polybrominated diphenyl ethers (OH-PBDEs; 93.8 +/- 19.5%), hydroxylated polychlorinated biphenyls (OH-PCBs; 93.8 +/- 15.5%), other halogenated phenols (OHPs; 107 +/- 8.1%), and for short-chain (<8 C-atoms) perfluoroalkyl substances (PFASs; 85.2 +/- 24.6%). In the same extracts, the potency of the compound classes spiked to the cow plasma to competitively bind to transthyretin (TTR) was recovered by 84.9 +/- 8.8%. Furthermore, the SPE-LLE method efficiently removed endogenous THs from the extracts, thereby eliminating their possible contribution to the binding assay response. The SPE-LLE method was applied to polar bear plasma samples to investigate its applicability in future EDA studies focusing on TH-disrupting compounds in this top predator species that is exposed to relatively high levels of bioaccumulating pollutants. A first screening revealed TTR-binding potency in the polar bear plasma extracts, which could be explained for 60-85% by the presence of OH-PCBs.