Tris Buffered Saline (TBS) is an isotonic, non-toxic buffer used in some biomedical techniques to maintain pH within a relatively narrow range.  TBS can shift pH relatively dramatically as temperature changes, with the pKa declining approximately 0.03 units per degree Celsius rise in temperature. Tris Buffered Saline (TBS) is an isotonic, non-toxic buffer used in some biomedical techniques to maintain pH within a relatively narrow range.  TBS can shift pH relatively dramatically as temperature changes, with the pKa declining approximately 0.03 units per degree Celsius rise in temperature.