What Is PBS? Phosphate-Buffered Saline Explained

PBS (phosphate-buffered saline) is one of the most common solutions in any cell culture lab. It is a simple, balanced salt solution used to rinse cells, dilute reagents, and keep cells in a stable, isotonic environment during handling. This guide explains what PBS is, what is in it, what it is used for, and how it differs from DPBS.

What is PBS?

PBS is a buffered salt solution that matches the pH and osmotic pressure of most mammalian cells. The phosphate buffer holds the pH near 7.4, and the salts keep the solution isotonic, so cells can sit in PBS briefly without being damaged. Unlike growth media, PBS contains no nutrients, so it is used for handling and washing rather than for culturing cells.

What is in PBS?

A standard PBS formulation contains:

• Sodium chloride and potassium chloride to set the salt balance and osmolarity
• Disodium phosphate and monopotassium phosphate, which form the buffer that holds pH around 7.4

Basic PBS does not contain calcium or magnesium. Some formulations add them (written “with Ca/Mg”), but calcium- and magnesium-free PBS is standard for many washing steps, especially before enzymatic detachment.

What is PBS used for?

PBS is a true workhorse, used to:

• Wash cells to remove serum, media, or debris (serum inhibits trypsin, so a PBS rinse before trypsinizing is standard)
• Dilute and prepare reagents at a physiological pH
• Rinse plates and dishes, and hold cells or tissue briefly during a protocol
• Serve as a base for many buffers used in immunostaining and other assays

PBS vs. DPBS

DPBS (Dulbecco’s phosphate-buffered saline) is a closely related formulation developed by Renato Dulbecco. It is similar to standard PBS but with a specific balance of salts, and it is available with or without calcium and magnesium. In practice the two are often used interchangeably for washing, though the exact formulation can matter for sensitive steps. For a direct comparison, see our guide on PBS vs DPBS.

How to use and store PBS

Use PBS at room temperature or gently warmed for washing live cells. For steps before enzymatic detachment, choose calcium- and magnesium-free PBS, since those ions support cell adhesion and interfere with dissociation. Store PBS as directed, keep it sterile, and avoid contamination, since it has no antimicrobial components of its own.