Influent wastewater samples that arrived at the lab were portioned into 50 mL samples and spiked with 50 ng of internal standard spiking mix (50 µL of a 1 µg mL -1 internal standard mix in MeOH). Samples were then frozen at this point, prior to the next steps. Samples, when fully defrosted, were filtered via GF/F filters before loading onto preconditioned Oasis HLB cartridges (2 mL of MeOH followed by 2 mL of miliq H2O). Preconditioning of cartridges occurred at a rate of 1 mL min -1 and samples were loaded at a rate of 5 mL min -1 . Once loaded, samples were dried under vacuum for at least 30 minutes. Elution from SPE cartridges was achieved using 4 mL of MeOH at a rate of 1 mL min -1 . The extracts were then dried under N2 using a TurboVap evaporator (Caliper, UK) at 40 °C. Reconstitution into polypropylene vials occurred with 500 μL of 80:20 H2O: MeOH. Samples were then stored at -18 °C until analysis.