Abstract
The values of the second dissociation constant pK2 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-Hückel 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 Ej 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. © ?2010 American Chemical Society.