Standards for pH Measurements of Bis-[(2-Hydroxyethyl)amino]acetic Acid (BICINE) from (278.15 to 328.15) K

Abstract

Abstract:The second dissociation constant, pK 2 , and related thermodynamic data for BICINE have been previously determined and reported from temperatures (278.15 to 328.15) K. For the present study, three buffer solutions without NaCl, and five with NaCl yielding an ionic strength (I = 0.16 mol·kg -1 ) similar to that of blood plasma were prepared. These buffer solutions have been evaluated in the temperature range of (278.15 to 328.15) K using the extended form of the Debye-Hückel equation. The Bates-Guggenheim convention is only valid when I< 0.1 mol·kg -1 . Values of the residual liquid junction potential (δE j ) between the BICINE solutions and the saturated KCl calomel electrode have been estimated at (298.15 and 310.15) K. Two BICINE buffer solutions are recommended as primary standard reference solutions for pH measurements of biological fluids.