Phosphate Buffered Saline (PBS) is a buffer solution commonly used in biological research. It is a balanced salty solution containing sodium chloride, sodium phosphate, and (in some formulations) potassium chloride and potassium phosphate. The buffer helps to maintain the pH constant. The osmolarity and ion concentrations of the solution usually match those of the human body (isotonic). PBS is used for a variety of cell culture applications, such as washing cells before dissociation, transporting cells or tissue, diluting cells for counting, and preparing reagents