Phosphate buffered saline (abbreviated PBS) is a buffer solution commonly used in biological research. It is a water-based salt solution containing sodium chloride, sodium phosphate, and (in some formulations) potassium chloride and potassium phosphate. The buffer helps to maintain a constant pH. The osmolarity and ion concentrations of the solution usually match those of the human body (isotonic). Synonyms: Phosphate Buffered Saline 10X Concentrate.