Abstract
Electromotive force (emf) measurements of the Cell Pt(s), H2(g)|ACES(m1) + NaACES(m2) + NaCl (m3)| AgCl, Ag(s) have been carried out from 5°C to 55°C . The agreement of pH values between two calculated (extended Debye-Huckel and liquid junction correction) is very good. Two buffer solutions without the chloride ion and seven buffer solutions with NaCl, at an ionic strength (I = 0.16 mol.kg-1) similar to that of physiological fluids, have been studied. The pH values for these buffer solutions have been evaluated in the temperature range of 5°C to 55°C using the extended Debye-Huckel equation of the Bates-Guggenheim convention. Values of the residual liquid junction potential (δEj) between the ACES solutions and the saturated KCl calomel electrode solution have been estimated at 25°C and 37°C from the previously determined Ej values using the flowing junction cell to determine the operational pH values at 25°C and 37°C. These ACES buffer solutions are recommended as secondary standard reference solutions for pH measurements in the range of physiological applicati on at I = 0.16 mol.kg-1.
Highlights
The zwitterionic amino acid buffer solutions recommended by Good et al [1,2] have been studied in the authors’ laboratory for the purpose of pH measurement control in the physiological range of pH
These ACES buffer solutions are recommended as secondary standard reference solutions for pH measurements in the range of physiological application at I = 0.16 mol·kg–1
The operational pH values at 25 ̊C and 37 ̊C were evaluated from cells with a liquid junction by means of the flowing junction cell [6,8]
Summary
The zwitterionic amino acid buffer solutions recommended by Good et al [1,2] have been studied in the authors’ laboratory for the purpose of pH measurement control in the physiological range of pH. Concerning the current investigation, the authors’ goal is to provide pH values for the ACES, which is depicted by the following structure: O. This phosphate buffer [3,4] is comprised of KH2PO4 (0.008695 mol·kg–1) and Na2HPO4 (0.03043 mol·kg–1). This buffer solution is widely used as the primary reference standard for routine laboratory measurements. Mol·kg–1) + NaACES (0.09 mol·kg–1) + NaCl (0.07 mol·kg–1); (h) ACES (0.02 mol·kg–1) + NaACES (0.08 mol·kg–1) + NaCl (0.08 mol·kg–1); (i) ACES (0.02 mol·kg–1) + NaACES (0.10 mol·kg–1) + NaCl (0.06 mol·kg–1)
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