0.1 M Sodium Phosphate Buffer Recipe
Introduction
Sodium phosphate buffers are commonly used in biochemical and molecular biology experiments to maintain a stable pH and ionic strength. In this article, we will provide a recipe for preparing a 0.1 M sodium phosphate buffer.
Materials
- Sodium phosphate dibasic (Na2HPO4)
- Sodium phosphate monobasic (NaH2PO4)
- Deionized water
Protocol
Step 1: Calculate the Amount of Sodium Phosphate Dibasic and Monobasic
To prepare a 0.1 M sodium phosphate buffer, you need to calculate the amount of sodium phosphate dibasic and monobasic required. The pKa of sodium phosphate is around 7.2, which means that at pH 7.2, the ratio of [Na2HPO4] to [NaH2PO4] is 1:1.
For a 0.1 M sodium phosphate buffer, you need to calculate the amount of sodium phosphate dibasic and monobasic as follows:
| Component | Molecular Weight | Moles Required | Grams Required |
|---|---|---|---|
| Na2HPO4 | 141.96 | 0.05 | 7.098 |
| NaH2PO4 | 119.98 | 0.05 | 5.999 |
Step 2: Weigh the Sodium Phosphate Dibasic and Monobasic
Weigh out the calculated amounts of sodium phosphate dibasic and monobasic using a balance.
Step 3: Dissolve the Sodium Phosphate Dibasic and Monobasic
Dissolve the weighed sodium phosphate dibasic and monobasic in approximately 800 mL of deionized water in a beaker. Stir the mixture until the solids are completely dissolved.
Step 4: Adjust the pH
Use a pH meter to adjust the pH of the solution to 7.2 by adding either sodium phosphate dibasic or monobasic.
Step 5: Filter the Solution
Filter the solution through a 0.22 μm filter to remove any impurities.
Step 6: Store the Buffer
Store the 0.1 M sodium phosphate buffer at room temperature or in the refrigerator at 4°C.
Tips and Variations
- To prepare a different concentration of sodium phosphate buffer, simply adjust the amount of sodium phosphate dibasic and monobasic used.
- To prepare a sodium phosphate buffer with a different pH, adjust the ratio of [Na2HPO4] to [NaH2PO4] accordingly.
- Always use deionized water to prepare the buffer to minimize the risk of contamination.
By following this recipe, you can prepare a 0.1 M sodium phosphate buffer that is suitable for use in various biochemical and molecular biology applications.
