Choose a buffer based on your pH requirements as well as the pKa, a measure of acid strength that accounts for pH, concentration, and temperature. Regulatory or purity needs for your exact application should also be considered. The following tables can help you navigate preparation of many common buffer solutions by pH and pKa.
Buffer grade indicates the quality and impurity levels appropriate for different uses. We provide six grades of buffers indicated for general lab use, final pharmaceutical formulation and manufacturing, and applications in between that may need trace metal testing or materials of a specified purity.
Na2HPO4 • 2H2O, MW 178.05; 0.2 M contains 35.61 g/L. Na2HPO4 • 12H2O, MW 358.22; 0.2 M contains 71.64 g/L. NaH2PO4 • H2O, MW 138.01; 0.2 M contains 27.6 g/L. NaH2PO4 • 2H2O, MW 156.03; 0.2 M contains 31.21 g/L.
x mL 0.2 M-Na2HPO4, y mL 0.2 M-NaH2PO4; diluted to 100 mL with H2O
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