Dec 31, 1998 · The pH was adjusted with 1 M NaOH solution. Before use, all buffer solutions were either filtered through a 0.45-μm Supor Acrodisc filter (for aqueous buffers) or a 0.45-μm GHP Acrodisc filter (for buffers with organic solvents) (Gelman, Ann Arbor, MI, USA) and sonicated 10 min to degas. 2.4. Procedures