Buffer Standards for pH Measurement of N-(2-Hydroxyethyl)piperazine-N′-2-ethanesulfonic Acid (HEPES) for I=0.16 mol⋅kg−1 from 5 to 55 °C

The values of the second dissociation constant, p K 2 , of N -(2-hydroxyethyl) piperazine- N ′-2-ethanesulfonic acid (HEPES) have been reported at twelve temperatures over the temperature range 5 to 55 °C, including 37 °C. This paper reports the results for the p a H of eight isotonic saline buffer...

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Bibliographic Details
Published in:Journal of solution chemistry 2009-04, Vol.38 (4), p.449-458
Main Authors: Roy, Rabindra N., Roy, Lakshmi N., Ashkenazi, Shahaf, Wollen, Joshua T., Dunseth, Craig D., Fuge, Michael S., Durden, Jared L., Roy, Chandra N., Hughes, Hannah M., Morris, Brett T., Cline, Kevin L.
Format: Article
Language:English
Subjects:
Chemistry
Chemistry and Materials Science
Condensed Matter Physics
Exact sciences and technology
General and physical chemistry
Geochemistry
Industrial Chemistry/Chemical Engineering
Inorganic Chemistry
Oceanography
Physical Chemistry
Solutions
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Summary:The values of the second dissociation constant, p K 2 , of N -(2-hydroxyethyl) piperazine- N ′-2-ethanesulfonic acid (HEPES) have been reported at twelve temperatures over the temperature range 5 to 55 °C, including 37 °C. This paper reports the results for the p a H of eight isotonic saline buffer solutions with an I =0.16 mol⋅kg −1 including compositions: (a) HEPES (0.01 mol⋅kg −1 ) + NaHEPES (0.01 mol⋅kg −1 ) + NaCl (0.15 mol⋅kg −1 ); (b) HEPES (0.02 mol⋅kg −1 ) + NaHEPES (0.02 mol⋅kg −1 ) + NaCl (0.14 mol⋅kg −1 ); (c) HEPES (0.03 mol⋅kg −1 ) + NaHEPES (0.03 mol⋅kg −1 ) + NaCl (0.13 mol⋅kg −1 ); (d) HEPES (0.04 mol⋅kg −1 ) + NaHEPES (0.04 mol⋅kg −1 ) + NaCl (0.12 mol⋅kg −1 ); (e) HEPES (0.05 mol⋅kg −1 ) + NaHEPES (0.05 mol⋅kg −1 ) + NaCl (0.11 mol⋅kg −1 ); (f) HEPES (0.06 mol⋅kg −1 ) + NaHEPES (0.06 mol⋅kg −1 ) + NaCl (0.10 mol⋅kg −1 ); (g) HEPES (0.07 mol⋅kg −1 ) + NaHEPES (0.07 mol⋅kg −1 ) + NaCl (0.09 mol⋅kg −1 ); and (h) HEPES (0.08 mol⋅kg −1 ) + NaHEPES (0.08 mol⋅kg −1 ) + NaCl (0.08 mol⋅kg −1 ). Conventional p a H values, for all eight buffer solutions from 5 to 55 °C, have been calculated. The operational pH values with liquid junction corrections, at 25 and 37 °C have been determined based on the NBS/NIST standard between the physiological phosphate standard and four buffer solutions. These are recommended as pH standards for physiological fluids in the range of pH = 7.3 to 7.5 at I =0.16 mol⋅kg −1 .
ISSN:0095-9782
1572-8927
DOI:10.1007/s10953-009-9378-3