0.1 M Phosphate Buffer Preparation
Introduction
Phosphate buffers are commonly used in biochemical and molecular biology applications to maintain a stable pH and provide a consistent ionic environment. In this article, we will outline the preparation of a 0.1 M phosphate buffer, a concentration widely used in various laboratory protocols.
Materials
- Sodium phosphate monobasic (NaH2PO4)
- Sodium phosphate dibasic (Na2HPO4)
- Distilled water
- pH meter
Preparation
- Calculate the amount of sodium phosphate monobasic and dibasic required:
To prepare 1 liter of 0.1 M phosphate buffer, you will need to calculate the amount of sodium phosphate monobasic and dibasic required. The molecular weights of sodium phosphate monobasic and dibasic are 119.98 g/mol and 141.96 g/mol, respectively.
For sodium phosphate monobasic (NaH2PO4):
- Molecular weight: 119.98 g/mol
- Amount required: 0.1 M x 1 L x 119.98 g/mol = 12.0 g
For sodium phosphate dibasic (Na2HPO4):
- Molecular weight: 141.96 g/mol
- Amount required: 0.1 M x 1 L x 141.96 g/mol = 14.2 g
- Weigh and dissolve the sodium phosphate monobasic and dibasic:
Weigh out 12.0 g of sodium phosphate monobasic and 14.2 g of sodium phosphate dibasic. Dissolve the salts in approximately 800 mL of distilled water.
- Adjust the pH:
Use a pH meter to measure the pH of the solution. Adjust the pH to the desired value (usually around pH 7.0) by adding either sodium phosphate monobasic or dibasic. Note: The pH of the solution will change as the salts dissolve.
- Dilute to final volume:
Once the pH is adjusted, dilute the solution to a final volume of 1 liter with distilled water.
- Filter sterilize (optional):
If the buffer is to be used in cell culture or other applications where sterility is critical, filter sterilize the solution through a 0.2 μm filter.
Storage
The prepared phosphate buffer can be stored at room temperature or refrigerated at 4°C for up to 6 months. Before use, check the pH and adjust if necessary.
Conclusion
The preparation of a 0.1 M phosphate buffer is a simple and straightforward process. By following these steps, you can ensure a stable and consistent buffer solution for your laboratory applications.
