Buffer Standards for Physiological pH of the Buffer N-(2-Acetamido)-2-aminoethanesulfonic Acid from 5°C to 55°C

Electromotive force (emf) measurements of the Cell Pt(s), H2(g)|ACES(m1) + NaACES(m2) + NaCl (m3)| AgCl, Ag(s) have been carried out from 5°C to 55°C . The agreement of pH values between two calculated (extended Debye-Hückel and liquid junction correction) is very good. Two buffer solutions without the chloride ion and seven buffer solutions with NaCl, at an ionic strength (I = 0.16 mol.kg-1) similar to that of physiological fluids, have been studied. The pH values for these buffer solutions have been evaluated in the temperature range of 5°C to 55°C using the extended Debye-Hückel equation of the Bates-Guggenheim convention. Values of the residual liquid junction potential (δEj) between the ACES solutions and the saturated KCl calomel electrode solution have been estimated at 25°C and 37°C from the previously determined Ej values using the flowing junction cell to determine the operational pH values at 25°C and 37°C. These ACES buffer solutions are recommended as secondary standard reference solutions for pH measurements in the range of physiological applicati on at I = 0.16 mol.kg-1.