Phosphate buffered saline

Phosphate buffer saline (abbreviated PBS) is a buffer solution commonly used in biochemistry. It is a salty solution containing sodium chloride, sodium phosphate and potassium phosphate. The buffer helps to maintain a constant pH. The concentration usually matches the human body (isotonic).

Applications
PBS has many uses because it is isotonic and non-toxic to cells. It can be used to dilute substances. It is used as a cellular cleaning solution. To ensure the prolonged dry-storage of immobilized-biomolecules like proteins, enzymatic proteins etc., PBS is used as biomolecule diluent since it can structure water around biomolecules immobilized to the solid surface. Such thin film of water prevents denaturing of biomolecules or conformational changes to them. Carbonate buffers may be used for the same purpose but with less effectiveness. PBS can be used as a reference spectra when measuring the protein adsorption in ellipsometry.

Additives can be used to add function. For example, PBS with EDTA is also used to disengage attached and clumped cells. Divalent metals such as zinc, however, cannot be added as this will cause precipitation. For these types of applications, Good's buffers are recommended.

Preparation
A 10 liter stock of 10x PBS can be prepared by dissolving 800 g NaCl, 20 g KCl, 144 g Na2HPO4 and 24g KH2PO4 in 8 L of distilled water, and topping up to 10 L. The pH is ~6.8, but when diluted to 1x PBS it should change to 7.4.

On dilution, the resultant 1x PBS will have a final concentration of 137 mM NaCl, 10 mM Phosphate, 2.7 mM KCl, pH 7.4