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Phosphate buffered saline (PBS) is a buffer solution commonly used in biochemistry. It is a physiological solution with sodium chloride, disodium phosphate, monopotassium phosphate and some potassium chloride. In general, the concentration of these salts is the same as in the human body (isotonicity).

This buffer is mainly used to rinse the cells when it is necessary to remove all traces of medium before processing them. It is intended for use on cells maintained outside the CO2 incubator and is not designed for long-term incubations. Its buffering capacity is based on the dihydrogen phosphate/hydrogen phosphate couple (pKA= 7.2), which is also one of the three main mechanisms for maintaining blood pH (HPO42- + H+ = H2PO4).