Buffer standards for the physiological pH of N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine (TRICINE) from T = (278.15 to 328.15) K

Abstract

The pH values of two buffer solutions without NaCl and seven buffer solutions with added NaCl, having ionic strengths (I=0.16mol·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 (δEj) 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(m1)=0.06mol·kg−1, NaTRICINE(m2)=0.02 mol·kg−1, and NaCl(m3)=0.14mol·kg−1, the pH values at T=310.15K 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.