Deuterium oxide 99.9%, sodium dihydrogenphosphate hydrate (NaH2PO4·H2O), disodiumhydrogen phosphate dihydrate (Na2HPO4·H2O2), and 3-(trimethylsilyl)propionic-2,2,3,3-d4 acid sodium salt (TSP) were purchased from Sigma-Aldrich (Milan, Italy). Deuterated EDTA d-16 98% was obtained from Product Cambridge Isotope Laboratories, Inc.
Phosphate buffer solution was prepared as follows: 49.7 mg of sodium dihydrogenphosphate hydrate (0.36 mmol), 202.9 mg of disodium hydrogen phosphate dihydrate (1.14 mmol), and 0.92 mg deuterated EDTA d-16 (0.003 mmol) were dissolved in 10 mL of water. The pH was checked at 7.1. The solution was distributed into 5 mL aliquots and then lyophilized. Each aliquot was dissolved in about 1 mL of D2O and lyophilized again. Finally, the buffer was dissolved in 5 mL of deuterium oxide with 0.002% TSP (12 mM).
Phosphate buffer solution was prepared as follows: 49.7 mg of sodium dihydrogenphosphate hydrate (0.36 mmol), 202.9 mg of disodium hydrogen phosphate dihydrate (1.14 mmol), and 0.92 mg deuterated EDTA d-16 (0.003 mmol) were dissolved in 10 mL of water. The pH was checked at 7.1. The solution was distributed into 5 mL aliquots and then lyophilized. Each aliquot was dissolved in about 1 mL of D2O and lyophilized again. Finally, the buffer was dissolved in 5 mL of deuterium oxide with 0.002% TSP (12 mM).