2 4 6 tcp

TCS, 2,4,6-TCP and 2,4-DCP (chemical purity ! 98.0%) were acquired from Sigma-Aldrich (St. Louis, USA), and their CAS No. and purities were summarized in Table S1. The stock solutions of three chemicals were prepared in acetone and stored at À20 C for use. The mixture of TCS, 2,4-DCP and 2,4,6-TCP is hereafter referred to as TCS-DT.

HPLC grade CPs standards, which included 4-CP, 2-CP, 2,4,6-TCP, 2,4-DCP, and 2,6-DCP, were purchased from Sigma-Aldrich (Shanghai, China) and the structures of CPs are shown in Supporting Information Fig. 1. Stock solutions of the standards were prepared as 1 g/L in MeOH and stored at 4°C in brown bottles. They were stable for at least 1 month. Working standard solutions containing all the CPs were freshly prepared by proper dilution of the stock standard solutions with ultrapure water. Chromatographic grade acetonitrile (ACN) and methanol (MeOH) were both purchased from J&K Chemical (Beijing, China). Other chemicals such as sodium hydroxide (NaOH) and sodium tetraborate decahydrate (Na 2 B 4 O 7 •10H 2 O) were of analytical grade and were obtained from Sinopharm Chemical Reagent (Shanghai, China). The water used throughout the work was produced by a Milli-Q ultrapure water system (Millipore, Bedford, MA, USA).
Lake water was taken from an artificial lake on the campus of Yantai University and tap water was taken from the laboratory and collected after 5 min of self-flow. During the collection, the glass containers were rinsed with river water and tap water respectively for three times. All water samples were filtered through microporous nylon filters with a pore diameter of 0.45 µm and then were stored in a refrigerator at 4°C for use.