Buffer Standards for the Physiological pH of the Zwitterionic Compound, ACES, from 5 to 55 deg C

• Published in: Journal of solution chemistry Vol. 38; no. 4; pp. 471 - 483
• Main Authors: Roy, Rabindra N, Roy, Lakshmi N, Fuge, Michael S, Roy, Chandra N, Himes, Curtis A, Bryant, Paul A, Robinson, Kyle T, Kaufmann II, Daniel A, Grove, Colby H, Gosh, Toshi, Bwashi, Adonis
• Format: Journal Article
• Language: English
• Published: 01.04.2009
• ISSN: 0095-9782; 1572-8927
• DOI: 10.1007/s10953-009-9380-9

The values of the second dissociation constant, pK 2, and related thermodynamic quantities of [N-(2-acetamido)-2-aminoethanesulfonic acid] (ACES) have already been reported over the temperature range 5 to 55 deg C including 37 deg C. This paper reports the pa H values of four chloride ion free buffer solutions and eight buffer solutions with I=0.16 mol.kg, matching closely that of the physiological sample. Conventional pa H values for all twelve buffer solutions from 5 to 55 deg C are reported. The residual liquid-junction potential correction for two widely used temperatures, 25 and 37 deg C, has been made. The flowing-junction calomel cell method has been utilized to measure E j, the liquid-junction potential. The operational pH values for four buffer solutions at 25 and 37 deg C are calculated using the physiological phosphate buffer standard based on the NBS/NIST convention. These solutions are recommended as pH standards in the pH range of 6.8 to 7.2 for physiological fluids.