Phosphate-buffered saline

Phosphate-buffered saline (abbreviated PBS) is a buffer solution commonly used in biological research. It is a water-based salt solution containing disodium hydrogen phosphate, sodium chloride and, in some formulations, potassium chloride and potassium dihydrogen phosphate. The osmolarity and ion concentrations of the solutions match those of the human body (isotonic).

Applications

PBS has many uses because it is isotonic and non-toxic to most cells. These uses include substance dilution and cell container rinsing. PBS with EDTA is also used to disengage attached and clumped cells. Divalent metals such as zinc, however, cannot be added as this will result in precipitation. For these types of applications, Good's buffers are recommended.

Preparation

There are many different ways to prepare PBS solutions (one of them is DPBS, or Dulbecco's phosphate-buffered saline, which has less phosphate concentration than normal PBS[1]). Some formulations do not contain potassium and magnesium, while other ones contain calcium and/or magnesium.[2]

The most common composition of PBS (1X)
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

Start with 800 mL of distilled water to dissolve all salts. Adjust the pH to 7.4 with HCl. Add distilled water to a total volume of 1 liter. The resultant 1x PBS should have a final concentration of 10 mM PO43−, 137 mM NaCl, and 2.7 mM KCl.

Cold Spring Harbor Protocol
reagent MW mass (g) 10X [M] 10X mass (g) 5X [M] 5X mass (g) 1X [M] 1X
Na2HPO4 141.95897 14.1960 0.1000 7.0980 0.0500 1.41960 0.0100
KH2PO4 136.08569 2.4496 0.0180 1.2248 0.0090 0.24496 0.0018
NaCl 58.44300 80.0669 1.3700 40.0335 0.6850 8.00669 0.1370
KCl 74.55150 2.0129 0.0270 1.0064 0.0135 0.20129 0.0027
pH = 7.4

The pH of the 10x stock solution of PBS is ~6.8, but when diluted with water to 1x PBS it should change to 7.4. When making buffer solutions, it is good practice to always measure the pH directly using a pH meter. If necessary, pH can be adjusted using hydrochloric acid or sodium hydroxide.

The simplest way to prepare a PBS solution is to use PBS buffer tablets or pouches. They are formulated to give a ready-to-use PBS solution upon dissolution in a specified quantity of distilled water. They are available in the standard volumes: 100, 200, 500 and 1000 mL, and 10, 25, 50 and 100 L.[3]

If used in cell culturing, the solution can be dispensed into aliquots and sterilized by autoclaving or filtration. Sterilization may not be necessary depending on its use. PBS can be stored at room temperature or in the refrigerator. However, concentrated stock solutions may precipitate when cooled and should be kept at room temperature until precipitate has completely dissolved before use.

See also

References

  1. ↑ Difference between phosphate-buffered saline (PBS) and Dulbecco's phosphate-buffered saline (DPBS)
  2. ↑ Dulbecco, R.; et al. (1954). "Plaque formation and isolation of pure lines with poliomyelitis viruses". J. Exp. Med. 99 (2): 167–182. doi:10.1084/jem.99.2.167. PMC 2180341Freely accessible. PMID 13130792.
  3. ↑ Medicago AB, (2010) Phosphate buffered saline specification sheet
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