The values of the second dissociation Constant pK(2) and related thermodynamic quantities of the ampholyte 3-[4-(2-hydroxyethyl)-1-piperazinyl]propanesulfonic acid (HEPPS) have already been published at temperatures from T = (278.15 to 328.15) K. The pH values of two equimolal buffer Solutions and eight buffer Solutions With ionic strengths similar to that of plasma in blood (I = 0.16 mol.kg(-1)) have been experimentally determined and then corrected at 12 temperatures from T = (278.15 to 328.15) K using the extended Debye-Huckel equation. The liquid junction potentials (E(j)) between the buffer solutions of HEPPS and the saturated KCl solution of the calomel electrode at (298.15 and 310.15) K have been estimated by measurement with the flowing junction cell. These values of E(j) have been used to ascertain the operational pH Values at T = (298.15 and 310.15) K. The zwitterionic buffer HEPPS was proven to be Useful through experimentation as a pH standard well within the region close to blood serum.