Edta 2na

Unless otherwise noted, all chemicals were commercially available and used as received without additional purification. Anhydrous citric acid, urea, CA, folic acid, ethylenediamine triacetic acid (EDTA)-2Na, biuret and the oxidised form of β-nicotinamide-adenine dinucleotide were purchased from J&K Scientific Ltd (Beijing) or Aladdin Chemicals Ltd (Shanghai). Deionised (DI) water (18.2 MΩ.cm at 25 °C) prepared by a Milli-Q water system was used throughout all experiments. Lake water samples were obtained from the Weiminghu Lake of Peking University, China. Before evaluation, the lake water samples were filtered through a 0.20 µm membrane and then centrifuged at 10,000 rpm for 10 min. The resultant water samples were spiked with Fe³⁺ at different concentrations and then analysed with the proposed method.

Hyperbranched polyester initiator, 220P, with an M_n of ca. 1600 g/mol (Weihai CY Dendrimer Technology Co., Ltd), mono-methoxyl PEG with an M_n of ca. 2000 g/mol (Aldrich), ε-caprolactone (CL, Acros, 99%), stannous octoate (Sn(Oct)₂, Aladdin, 95%), 4-pentynoic acid (J&K Scientific Ltd., 95%), N, N-dicyclohexylcarbodiimide (DCC, J&K Scientific Ltd., 99%), 4-dimethylaminopyridine (DMAP, TCI, 99%), 2-bromoisobutyryl bromide (Acros, 98%), trimethylamine (TCI, Shanghai, 99%), tris(2-dimethylaminoethyl)amine (ME6-TRAN, Alfa Aesar, 99%), N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA, Aldrich, 99%), dichloromethane (CH₂Cl₂, J&K Scientific Ltd., 99.8%), Ethylenediaminetetraacetic acid disodium salt (EDTA-2Na, J&K Scientific Ltd.) and N,N-dimethylformamide (DMF, J&K Scientific Ltd., 99.9%) were used as received. 2-diethylaminoethyl methacrylate (DEAEMA, J&K Scientific Ltd., 99.5%) was purified by passing through a basic alumina column. Copper (I) bromide (CuBr, J&K Scientific Ltd., 98%) was purified by stirring with acetic acid overnight, filtered, and then successively washed with acetone and ethanol until it turned white, followed by complete drying in a vacuum oven at room temperature. Other solvents were purchased from Beijing Chemical Reagent Co. Ltd (China) and used as received. Deionized and distilled water was utilized throughout the study.