0.2 M sodium phosphate buffer (pH 7.2) recipe
Sørensen phosphate buffer made from Na₂HPO₄ and NaH₂PO₄. Diluted 1:1 to 0.1 M, it is the usual base for glutaraldehyde and PFA fixatives.
🧮 Volume calculator
| Component | Amount | Final concentration (1X) |
|---|---|---|
| Na₂HPO₄ (anhydrous) | 10.22 g | 144 mM |
| NaH₂PO₄·H₂O | 3.865 g | 56 mM |
| Water (distilled) | to final volume |
Steps
- Dissolve in about 80% of the final volume of water.
- Check the pH and adjust slightly if needed.
- Bring to the final volume with water.
- Autoclave (121 °C, 20 min) and store at room temperature.
Good to know
- For pH 7.4 use Na₂HPO₄ 23.0 g + NaH₂PO₄·H₂O 5.24 g per litre (81 : 19).
- With Na₂HPO₄·7H₂O multiply the anhydrous amount by 1.888.
FAQ
Crystals formed in the cold.
Concentrated sodium phosphate precipitates at 4 °C. Store at room temperature and warm to redissolve.
This is a widely used standard composition. Amounts depend on the hydrate form and purity of your reagents — check the formula weight (FW) on the bottle and follow your institution's safety rules and the manufacturers' instructions.