Bw30le

PEI (M_w = 50 kg mol⁻¹, 50 wt.% in H₂O, Sigma-Aldrich, St. Louis, MO, USA), PAA (M_w = 100 kg mol⁻¹, 35 wt.% in H₂O, Sigma-Aldrich), PIP (99%, Sigma-Aldrich), MPD (99%, Sigma-Aldrich), TMC (>98.0%, TCI), hydrochloric acid (HCl, 35%, Daejung Chemical, Siheung, South Korea), NaCl (99.5%, Daejung Chemical), sodium hydroxide (NaOH, 98%, Daejung Chemical), n-hexane (99.5%, Daejung Chemical) were used as received. Deionized (DI) water (18.2 Ω) was prepared using a Millipore Milli-Q purification system. Polyacrylonitrile (PAN) ultrafiltration membranes (PAN50) were purchased from Nanostone Water (Waltham, MA, USA). Commercial RO membranes (SW30LE, SW30HR, BW30, and BW30LE from Dow Filmtec, Wilmington, DE, USA and SWC4+ from Hydranautics, Oceanside, CA, USA) were obtained from the manufactures.

The chemicals used were of analytical grade: n-propanol (≥99%, VWR Chemicals BDH Prolabo, Rosny-sous-Bois, France), sodium chloride (p.a., Lach-Ner, Neratovice, Czech Republic), calcium chloride (p.a., Lach-Ner, Neratovice, Czech Republic). N-nitrosamines used were as follows: N-nitrosodiethylamine (99%, Aldrich, St. Louis, MO, USA), N-nitrosodi-n-propylamine (99.9%, Supelco, St. Louis, MO, USA) and N-nitrosodi-n-butylamine (99.9%, Supelco, St. Louis, MO, USA). HPLC-grade acetonitrile (J. T. Baker, Deventer, The Netherlands) and ultra-pure water prepared using the Milli-Q^® Reagent Grade Water System (Millipore Corporation, Bedford, MA, USA) were used for chromatographic analysis. Organic compounds selected as markers were as follows: trimethylene oxide (97%, Acros Organics, Morris Plains, NJ, USA), 1,3-dioxolane (99.8%, Sigma-Aldrich, St. Louis, MO, USA), 1,4-dioxane (99.8%, Sigma-Aldrich, St. Louis, MO, USA), 12-crown-4 (98%, Fluka, Buchs, Switzerland), 15-crown-5 (98%, Merck-Schuchardt, Hohenbrunn, Germany), and 18-crown-6 (99.5%, Fluka, Buchs, Switzerland). Commercial RO membranes BW30LE (DOW FILMTEC™, Wilmington, DE, USA), UTC-73AC (Toray™, Poway, CA, USA) and ACM1 (TriSep™, Goleta, CA, USAwere supplied from Sterlitech Corporation, Auburn, WA, USA as flat sheets and stored dry before use. Nominal membrane characteristics provided by the manufacturer are given in Table 3.