4.2.1. Chemicals

Analytical grade methanol, K2HPO4·3H2O, NaH2PO4·2H2O and sodium azide (NaN3) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Sodium 3-trimethylsilyl [2,2,3,3−2H4]-propionate (TSP) and deuterium oxide (D2O, 99.9% D) were purchased from Cambridge Isotope Laboratories, Inc. (Tewksbury, MA, USA). The phosphate buffer for NMR analysis was prepared by dissolving K2HPO4 and NaH2PO4 in water (0.15 M, pH 7.44, K2HPO4/NaH2PO4 = 4:1) containing 0.001% TSP, 0.1% NaN3, and 50% D2O [54].
