PBS (phosphate-buffered saline) recipe
The most widely used isotonic buffer for washing cells, dilutions and antibody incubations. 1X is 137 mM NaCl, 2.7 mM KCl, 10 mM Na₂HPO₄ and 1.8 mM KH₂PO₄ at pH 7.4.
| Component | Amount | Final concentration (1X) |
|---|---|---|
| NaCl | 8 g | 137 mM |
| KCl | 200 mg | 2.7 mM |
| Na₂HPO₄ (anhydrous) | 1.44 g | 10 mM |
| KH₂PO₄ | 240 mg | 1.8 mM |
| Water (distilled) | to final volume |
Concentrated stocks (e.g. 10X) contain every component at that multiple — dilute to 1X for use.
Steps
- Dissolve all components in about 80% of the final volume of water.
- Adjust to pH 7.4 (10X stocks are often made so the 1X dilution reads 7.4).
- Bring to the final volume.
- Autoclave (121 °C, 20 min) or filter, and store at room temperature.
Good to know
- With Na₂HPO₄·7H₂O use 2.68 g per litre of 1X; with the dihydrate (·2H₂O) use 1.78 g.
- 10X PBS can precipitate phosphate in the cold — warm to redissolve before use.
- For cell culture, use Ca²⁺/Mg²⁺-free PBS (DPBS −/−) before trypsin.
FAQ
What is the difference between PBS and DPBS?
DPBS (Dulbecco's PBS) has slightly different phosphate levels and is also sold with Ca²⁺/Mg²⁺. Both work for washing and dilution, but use the Ca/Mg-free form when detaching cells.
When should I use TBS instead of PBS?
Use TBS when phosphate could interfere, e.g. with alkaline phosphatase detection or some phospho-specific antibodies.
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.