0.5 M EDTA (pH 8.0) recipe
A chelator that traps metal ions and inhibits enzymes such as DNases. EDTA only dissolves near pH 8, so add NaOH while dissolving.
🧮 Volume calculator
| Component | Amount | Final concentration (1X) |
|---|---|---|
| Disodium EDTA dihydrate (Na₂EDTA·2H₂O) | 93.05 g | 0.5 M |
| NaOH pellets | 10 g | to pH 8.0 (≈ 20 g/L) |
| Water (distilled) | to final volume |
Steps
- Add EDTA to about 80% of the final volume of water and stir (it will not dissolve yet).
- Add NaOH gradually — the solution clears as the pH approaches 8.0.
- Adjust to pH 8.0 and bring to the final volume.
- Autoclave and store at room temperature.
Good to know
- EDTA free acid (MW 292.24, 146.1 g/L) needs much more NaOH.
⚠ Safety NaOH releases heat when dissolving and burns skin — wear gloves and goggles.
FAQ
Why won't it dissolve?
Disodium EDTA only dissolves near pH 8. Add more NaOH to raise the pH.
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.