Optimized Extraction and Derivatization of POPs

Adipose (0.03-0.11 g), brain (0.08-0.14 g) or liver (0.15-0.29 g) samples were thoroughly mixed with 2 g of pre-extracted diatomaceous earth and placed in the 33 mL extraction cell over 12 g of pre-extracted Florisil. The cells were spiked with the surrogate standard (50 ng PCB 117 in 0.1 mL isooctane; 68.5 ng 4-159 in 50 μL isooctane). The samples were extracted with hexane:dichloromethane:methanol (48:43:9, v/v) at 100 °C, 1500 psi (10 MPa) with pre-heat equilibration of 6 min, 35% cell flush volume and 1 static cycle of 5 min using a pressurized solvent extraction system (ASE 200, Dionex, Sunnyvale, CA).^{34 (link)} The extracts were concentrated to approximately 1 mL in a TurboVap (43 °C, 5 psi; Caliper Life Sciences, Hopkinton, Massachusetts) and derivatized with diazomethane to convert hydroxylated PCBs (OH-PCBs) into methoxylated derivatives. Afterwards, samples were subjected to a sulfur clean-up step, as described previously.^{18 (link),34 (link)}Whole blood (0.10-0.45 g) was spiked with the surrogate standard (50 ng PCB 117 in 0.1 mL isooctane; 68.5 ng 4-159 in 50 μL isooctane) and treated with hydrochloric acid to denature proteins.^{35 (link)} Samples were then extracted with 2-propanol and hexane-MTBE mixture (5 mL, 1:1, v/v). The organic extracts were washed with potassium chloride and the solvent was exchanged to hexane. Afterwards, the samples were derivatized with diazomethane and subjected to a sulfur clean-up step, as described previously.^{18 (link),34 (link)}