Endosulfan (96.20%) was provided by Jiangsu Red Sun Limited
Company (Nanjing, China). Micro-scale zinc and iron powder
(analytical grade) were purchased from Sinopharm Chemical Reagent
Co., Ltd (Shanghai, China). Anhydrous sodium sulfate, ethyl
acetate, cetyl pyridinium chloride (CPC), sodium dodecyl sulfate
(SDS) and tween-20 (TW-20) of analytical grade were purchased
from Solarbio Company (Beijing, China). Acetate buffer (pH 4),
phosphate buffer (pH 7), and carbonate buffer (pH 9) were prepared
according to standard methods.