Choosing the Right Buffer

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.

What are buffer grades?

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.

Useful pH Ranges of Selected Biological Buffers Chart (25 °C, 0.1 M)

Tris or Trizma® Buffer Preparation Table – pH vs. Temperature

Phosphate Buffer Preparation Table – 0.2 M solution

Citric Acid – Na2HPO4 Buffer Preparation, pH 2.6–7.61

Citric acid monohydrate, C6H8O7 • H2O, MW 210.14; 0.1 M contains 21.01 g/L. Na2HPO4, MW 141.98; 0.2 M contains 28.40 g/L, or Na2HPO4 • 2H2O, MW 178.05; 0.2 M contains 35.61 g/L.

x mL 0.1 M-citric acid and y mL 0.2 M-Na2HPO4 mixed

Citric Acid – Sodium Citrate Buffer Preparation, pH 3.0-6.21

Citric acid monohydrate, C6H8O7 • H2O, MW 210.14; 0.1 M contains 21.01 g/L. Trisodium citrate dihydrate, C6H5O7Na3 • 2H2O, MW 294.12; 0.1 M contains 29.41 g/L.

x mL 0.1 M-citric acid and y mL 0.1 M-trisodium citrate mixed

Sodium Acetate – Acetic Acid Buffer PREPARATION, pH 3.7–5.61

Sodium acetate trihydrate, CH3COONa • 3H2O, MW 136.09; 0.2 M contains 27.22 g/L.

x mL 0.2 M-NaOAc and y mL 0.2 M-HOAc mixed

Na2HPO4 – NaH2PO4 Buffer PREPARATION, pH 5.8-8.0 at 25 °C1

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

Imidazole (glyoxaline) – HCl Buffer PREPARATION, pH 6.2–7.8 at 25 °C1

Imidazole, C3H4N2, MW 68.08

25 mL 0.2 M-imidazole (13.62 g/L), x mL 0.2 M-HCl, diluted to 100 mL with H2O

Sodium Carbonate – Sodium Bicarbonate Buffer PREPARATION, pH 9.2-10.81

Na2CO3 • 10H2O, MW 286.2; 0.1 M contains 28.62 g/L. NaHCO3, MW 84.0; 0.1 M contains 8.40 g/L.

x mL 0.1 M-Na2CO3 and y mL 0.1 M-Na2HCO3 mixed

Buffer Preparation Formulas and Equations

Percentage by weight (w/v)

(% buffer desired / 100) × final buffer volume (mL) = g of starting material needed.

Molar Solutions

desired molarity × formula weight × solution final volume (L) = grams needed

Henderson-Hasselbach Equation

Henderson ph

Reference

1.
Dawson R, Elliot D, Elliot W, Jones KM. 1986. Data for Biochemical Research. 3rd ed.. Oxford Science Publ..