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).

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.

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

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.

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.

If used in cell culturing, the solution can be dispensed into aliquots and sterilized by 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.

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