Analytical standards (99.9% purity) for triclosan (TCS) and methyltriclosan (MTCS) were purchased from Sigma-Aldrich, Shanghai, China. The chemical structure and molecular weight of TCS and MTCS are shown in Supplementary Fig. 1. Five medium-chain fatty acids (pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid and nonanoic acid) were purchased from J&K Chemical, Shanghai, China. HPLC-grade methanol, ethanol, ethylene glycol, acetone, acetonitrile, and dimethyl sulfoxide were purchased from Merck, Shanghai, China.
Stock standard solutions (1000 μg mL -1 ) for TCS and MTCS were prepared by dissolving each chemical in methanol and stored at 4 °C until use. Working solutions were diluted with Milli-Q 18 MΩ ultrapure water (Millipore, Bedford, MA, USA) and methanol (v/v = 50:50) to prepare secondary mixed stock solutions. All working solutions were prepared fresh weekly and stored at 4 °C.
Stock standard solutions (1000 μg mL -1 ) for TCS and MTCS were prepared by dissolving each chemical in methanol and stored at 4 °C until use. Working solutions were diluted with Milli-Q 18 MΩ ultrapure water (Millipore, Bedford, MA, USA) and methanol (v/v = 50:50) to prepare secondary mixed stock solutions. All working solutions were prepared fresh weekly and stored at 4 °C.