Buffer Standards for the Biological pH of the Amino Acid N-[2-Hydroxyethyl]piperazine-N′-[3-propanesulfonic acid], HEPPS, From (278.15 to 328.15) K

For the HEPPS buffer under investigation, there are seven buffer solutions without NaCl and eight buffer solutions that contain Cl– and have an ionic strength (I = 0.16 mol·kg–1) that is similar to that of blood plasma. These buffer solutions have been evaluated in the temperature range of (278.15 to 328.15) K using the extended Debye–Hückel equation and the Bates–Guggenheim convention. The previously determined E j values have been used to determine the operational pH values of HEPPS buffer solutions at (298.15 and 310.15) K. These are recommended as secondary standard reference solutions for pH measurements in saline media with an isotonic ionic strength of I = 0.16 mol·kg–1.