Ferguson, W.J., Braunschweiger, K.L., Braunschweiger, W.R., Smith, J.R., McCormick, J.J., Wasman, C.C., Jarvis, N.P., Bell, D.H. and Good, N.E. (1980) Hydrogen Ion Buffers for Biological Research. Analytical Chemistry, 104, 300-310.

has been cited by the following article:

• TITLE: Thermodynamics of the Second Dissociation Constants (pK2) of Piperazine-N,N′-bis-2-hydroxypropanesulfonic Acid (POPSO Sesquisodium Salt) and Associated Thermodynamic Functions from (278.15 to 328.15) K

  AUTHORS: Rabindra N. Roy, Lakshmi N. Roy, Katherine E. Hundley, Taylor R. Wehmeyer, Lucas S. Tebbe

  KEYWORDS: pH, Buffer Compound, Liquid Junction, Thermodynamic Functions, Activity Coefficients, Electromotive-Force, pK2

  JOURNAL NAME: Journal of Biophysical Chemistry, Vol.5 No.4, November 24, 2014

  ABSTRACT: The second acidic dissociation constants of protonated piperazine-N,N′-bis-2-hydroxypropane-sulfonic acid (POPSO sesquisodium salt) have been determined at 12 different temperatures from (278.15 to 328.15) K including 310.15 K. Electromotive-force measurement technique was used employing hydrogen-silver chloride cells without liquid junction. The results of pK2 are given by the equation: pK2 = -1041.77/T + 51.0459 - 6.97646lnT. The uncertainty of the fit is ±0.0008. At 289.15 K, pK2 = 7.8029; whereas, at 310.15 K (body temperature), pK2 = 7.6862. Thus, the buffer solutions of POPSO and its sodium salt are useful for pH control in the physiological pH region of (7.0 to 8.5). The changes of Gibbs free energy (G°), enthalpy (H°), entropy (S°) and heat capacity Cp° were computed from the temperature derivative of the pK2 for the dissociation of the zwitterionic acid POPSO±-3 = POPSO-4 + H+ in the standard state. At 298.15 K, these results are compared with those of similar components, which are the derivatives of the parent compounds TAURINE, PIPERAZINE and MORPHOLINE.