2.9. Solvent extraction (SE)
A 0.2 g sample was weighed and put into a 15 mL tube with a screw top, sonicated at room temperature for 15
minutes and centrifuged at 4000 rpm for 15 minutes. These steps were repeated for 5 times using different solvents
including water, methanol, acetone, water at 90°C, 0.1 M TFA at 90°C, and TFA microwave. The supernatant of
each extract was collected14. Final pellet was collected and dried in an oven at 70°C overnight. The dry pellets were
digested in nitric acid using a Microwave digester Ultraclave III. Each supernatant was measured by GF-AAS as
total arsenic. The method was validated using the analysis of DORM-2 (dogfish muscle tissue certificate [As] =
18.0±1.1 μg g-1 found [As] 19.68±1.16 μg g-1, n=3).