Samples were
extracted once with acetone containing 0.1 mL L−1 (v/v) HCl, followed
by extracting twice with 700 mL L−1 (v/v) aqueous acetone
containing 0.1% mL L−1 (v/v) HCl under ultrasonication (S-10H,
Zealway instrument Inc., Xiamen, China) for 30 min.