2.1 Chemicals and Reagents
All aqueous solutions were prepared using ultrapure water (18.2 MΩ∙cm) obtained from a Milli-Q water purification system (Millipore Sigma). All chemicals and reagents were used as received, without further purification. Buffers containing 0.001% (w/v) Pluronic F-68 were prepared from a 10% (w/v) Gibco Pluronic F-68 (Thermo Fisher Scientific) stock solution. ­Sodium chloride (NaCl), ≥99%; and magnesium chloride (MgCl2) hexahydrate, ≥98%, USP grade were purchased from J.T. Baker. Tetramethylammonium chloride (TMAC), ≥98%; tetrabutylammonium chloride (TBAC) hydrate, ≥96%; tetraethylammonium acetate (TEA-Ac), ≥97%; and tetraethylammonium tetrafluoroborate (TEA-BF4), ≥99% were purchased from Acros Organics. Tetraethylammonium chloride (TEAC) monohydrate, ≥98% and tetraethylammonium bromide (TEAB), ≥98% were purchased from Alfa Aesar. Tetrapropylammonium chloride (TPAC), ≥97% was purchased from TCI America. Bis-tris propane (BTP), ≥98% was purchased from Sigma-Aldrich. Tris(hydroxymethyl) aminomethane (Tris), Emprove Essential, USP grade was purchased from Millipore Sigma. Tris(hydroxymethyl)aminomethane hydrochloride), (Tris-HCl), ≥99%, USP grade; and 6 N hydrochloric acid solution were purchased from J.T. Baker.