The whole supernatant was removed,diluted to 250 mL with water, acidified to pH = 2 with HCl 6 M,and passed through the preconditioned Carbograph-4 cartridge.Then, the cartridge was washed with 10 mL of water, and PFAS were eluted with 10 mL of methanol/dichloromethane (1:1, v/v),