Reagents
were prepared as follows: (A) pH 3.6 acetate buffer was prepared by
adjusting the pH of a 300 mM aqueous NaOAc solution to 3.6 with
HOAc/distilled H2O; (B) 10 mM 2,4,6-trispyridyl-s-triazine (TPTZ)
was prepared by making a solution of 10 mM TPTZ in 40 mM HCl;