Buffer Standards for the Physiological pH of the Zwitterionic Compound, HEPPSO from 5 to 55 °C

• Published in: Journal of solution chemistry Vol. 38; no. 11; pp. 1417 - 1431
• Main Authors: Roy, Rabindra N., Roy, Lakshmi N., Denton, Cole E., LeNoue, Sean R., Dunseth, Craig D., Fuge, Michael S., Ashkenazi, Shahaf, Durden, Jared L., Roy, Chandra N., Wollen, Joshua T., Hayden, Shawn M.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 2009
• Subjects: Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Geochemistry; Industrial Chemistry/Chemical Engineering; Inorganic Chemistry; Oceanography; Physical Chemistry; Ionic strength; HEPPSO; pH; Liquid junction; Buffers; Zwitterions; Acidity function; Emf
• ISSN: 0095-9782; 1572-8927
• DOI: 10.1007/s10953-009-9442-z

The values of the thermodynamic second dissociation constant, p K 2 , and related thermodynamic quantities of N-(2-hydroxyethyl)piperazine-N′-2-hydroxypropanesulfonic acid (HEPPSO) have already been reported from 5 to 55 °C, including 37 °C, by the emf method. This paper reports the results for the pH of one chloride-free buffer solution containing the composition: (a) HEPPSO (0.08 mol⋅kg −1 )+NaHEPPSO (0.04 mol⋅kg −1 ). The remaining seventeen buffer solutions contain a saline medium of ionic strength I =0.16 mol⋅kg −1 , matching closely that of physiological fluids. Conventional pH values, denoted as p a H , for all eighteen buffer solutions from 5 to 55 °C have been calculated. The operational pH values, designated as pH, with residual liquid-junction corrections for five buffer solutions, one without NaCl, and four with buffer solutions in saline media of I =0.16 mol⋅kg −1 are recommended as pH standards in the range of physiological application. These are based on the NBS/NIST standard scale for pH measurements.