Buffer Standards for the Physiological pH of N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine (TRICINE) from T =...

The pH values of two buffer solutions without NaCl and seven buffer solutions with added NaCl, having ionic strengths (I = 0.16 mol·kg(-1)) similar to those of physiological fluids, have been evaluated at 12 temperatures from T = (278.15 to 328.15) K by way of the extended form of the Debye-Hückel equation of the Bates-Guggenheim convention. The residual liquid junction potentials (δE(j)) between the buffer solutions of TRICINE and saturated KCl solution of the calomel electrode at T = (298.15 and 310.15) K have been estimated by measurement with a flowing junction cell. For the buffer solutions with the molality of TRICINE (m(1)) = 0.06 mol·kg(-1), NaTRICINE (m(2)) = 0.02 mol·kg(-1), and NaCl (m(3)) = 0.14 mol·kg(-1), the pH values at 310.15 K obtained from the extended Debye-Hückel equation and the inclusion of the liquid junction correction are 7.342 and 7.342, respectively. These are in excellent agreement. The zwitterionic buffer TRICINE is recommended as a secondary pH standard in the region for clinical application.