What is PBS Buffer?
PBS is short of phosphate-buffered saline. It is a water-based buffered salt solution that helps maintain a constant pH in a sample. It is a buffer solution that is widely used in biological research, especially in experiments involving living cells.
PBS (Phosphate Buffered Saline) is a pH-adjusted mixture of high-purity phosphate buffers and saline containing 137mM NaCl, 2.7mM KCl, 8mM Na2HPO4, and 2mM KH2PO4 when diluted to 1X working concentration. Each 10X PBS solution is ready to use after dilution to the desired concentration.
PBS salt buffer solution helps maintain a constant pH of the sample outside the growth medium and maintains cell osmolarity because the water level and ionic concentration of the PBS solution are the same as the human body, which means the PBS solution is isotonic in Nature.
Because PBS solutions are non-toxic to cells, they have many uses including substance dilution and detachment of clumped cells, etc. In recent years, PBS solutions have been in high demand as they are used as an alternative to viral transport media for RNA storage Viruses like SARS-CoV-2 or Coronavirus.
A PBS solution can be prepared by various methods. When the buffer is used on living tissue, the preparation requires potassium chloride or magnesium chloride, while when the buffer is used on fixed tissue, neither potassium chloride nor magnesium chloride is required. During the preparation, the pH value can be adjusted with hydrochloric acid or sodium hydroxide.
The most common components of a PBS solution are NaCl, KCl, Na2HPO4, and KH2PO4 in precisely calculated amounts. PBS solutions can also be prepared using commercially manufactured PBS-buffered tablets or capsules. PBS solutions are stored either at room temperature or in the refrigerator.
What Is The Chemical Composition Of The PBS Buffer Solution?
There are several recipes for making PBS solutions. The essential solution contains water, sodium hydrogen phosphate, and sodium chloride. Some preparations contain potassium chloride and potassium dihydrogen phosphate. EDTA can also be added to cell preparations to prevent clumping.
Phosphate-buffered saline is not ideal for use in solutions containing divalent cations (Fe2+, Zn2+) as precipitation may occur. However, some PBS solutions contain calcium or magnesium. Also, remember that phosphate can inhibit enzymatic reactions.
Be especially aware of this potential downside when working with DNA. While PBS is great for physiological science, be aware that the phosphate in a PBS-buffered sample can precipitate when the sample is mixed with ethanol.
A typical 1X PBS Chemical Composition has a final concentration of 10 mM PO43−, 137 mM NaCl, and 2.7 mM KCl. Here is the final concentration of the reagents in the solution:
| Salt | Concentration (mmol/L) | Concentration (g/L) |
| NaCl | 137 | 8.0 |
| KCl | 2.7 | 0.2 |
| Na2HPO4 | 10 | 1.42 |
| KH2PO4 | 1.8 | 0.24 |
PBS Versus DPBS
Another popular buffer solution is Dulbecco’s phosphate-buffered saline or DPBS. Like PBS, DPBS is used for biological research and as a buffer in the pH range of 7.2 to 7.6. It can be stored at room temperature. Dulbecco’s solution contains a lower concentration of phosphate. It is an 8.1mM phosphate ion while normal PBS contains 10mM phosphate. The recipe for 1x DPBS is:
| Reagent | Amount to add (1x) |
| NaCl | 8.007 g |
| KCl | 0.201 g |
| Na2HPO4 | 1.150 g |
| KH2PO4 | 0.200 g |
| Optional: | |
| CaCl2•2H2O | 0.133 g |
| MgCl2•6H2O | 0.102 g |
Dissolve the salts in 800 ml of water. Adjust the pH to between 7.2 and 76 with hydrochloric acid. Adjust the final volume to 1000 mL with water. Autoclave at 121°C for 20 minutes.
