Phosphate buffered saline

Wikipedia, the free encyclopedia - Cite This Source

Phosphate buffered saline (abbreviated PBS) is a buffer solution commonly used in biochemistry. It is a salty solution containing sodium chloride, sodium phosphate, and (in some formulations) potassium chloride 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

There are many different ways to prepare PBS. Some formulations do not contain potassium, while others contain calcium or magnesium. One of the most common preparations is described below.

A 10 liter stock of 10x PBS can be prepared by dissolving 800 g NaCl, 20 g KCl, 144 g Na₂HPO₄ and 24 g 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. When making buffer solutions, it is good practise to always measure the pH directly using a pH meter. For PBS, the pH can be adjusted using hydrochloric acid or sodium hydroxide.

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

External links

Wikipedia, the free encyclopedia © 2001-2006 Wikipedia contributors (Disclaimer)
This article is licensed under the GNU Free Documentation License.
Last updated on Thursday February 28, 2008 at 06:12:40 PST (GMT -0800)
View this article at Wikipedia.org - Edit this article at Wikipedia.org - Donate to the Wikimedia Foundation