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 result in 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[1]. One of the most common preparations is described below.
The simplest way to prepare a PBS solution is to use PBS buffer tablets. 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 [2].
A 10 liter stock of 10x PBS can be prepared by dissolving 800 g NaCl, 20 g KCl, 144 g Na2HPO4 and 27 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 practice to always measure the pH directly using a pH meter. If necessary, 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, 2.7 mM KCl, 10 mM Sodium Phosphate dibasic, 2 mM Potassium Phosphate monobasic and a pH of 7.4.
Another preparation is described in Molecular Cloning by Sambrook, Fritsch and Maniatis, Apendix B.12[3] as follows:
For 1 litre of 1x Phosphate-buffered saline (1x PBS buffer) use:..
References
1^ Dulbecco, R. et al. (1954): Plaque formation and isolation of pure lines with poliomyelitis viruses. In: J. Exp. Med. vol. 99 (2), pp. 167-182. PMID 13130792
2^ Medicago AB, (2003) Phosphate buffered saline pH 7.4 specification sheet
3^ Sambrook, Fritsch, and Maniatis (1989) Molecular Cloning: A Laboratory Manual, 2nd ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York, volume 3, appendix B.12