Potentiometric studies of the rutile-water interface: Hydrogen-electrode concentration-cell versus glass-electrode titrations

Moira K. Ridley, Michael L. Machesky, Donald A. Palmer, David J. Wesolowski

Research output: Contribution to journalArticlepeer-review


This paper represents a comparison of surface protonation studies of rutile in NaCl media obtained using a conventional glass-electrode autotitrator system from 10 to 50°C, and hydrogen-electrode concentration cells from 25 to 250°C [J. Colloid Interface Sci., 200 (1998) 298]. Experimental conditions were matched as closely as possible between the two techniques, permitting a direct comparison of the results. Values for the pH of zero net proton charge (pHznpc) of the rutile surface obtained at 10 and 35°C were consistent with the temperature trends observed previously using hydrogen-electrode concentration cells. The pHznpc of rutile decreases systematically from 5.7 to 4.2 as temperature increases from 10 to 250°C. Moreover, the experimentally determined pHznpc values agree with independent estimates of the pH at the pristine point of zero charge (pHznpc) calculated from an extension of the revised Multi-Site Complexation (MUSIC) Model of Hiemstra et al. [J. Colloid Interface Sci., 184 (1996) 680]. Surface protonation curves obtained from the glass-electrode titration results were rationalized using surface protonation constants derived from the MUSIC Model, in conjunction with a Basic Stern representation of the electrical double layer (EDL) structure. Best-fit parameters (Stern layer capacitance values, and electrolyte cation and anion binding constants) are consistent with those obtained from fits to titration curves obtained using hydrogen-electrode concentration cells at 25 and 50°C. Consequently, this comparison demonstrates that independent conventional glass-electrode and hydrogen-electrode concentration cell titrations provide completely compatible results despite the intrinsic differences in the two techniques (pH calibration, equilibration times, stirring rates, gas phase composition, etc).

Original languageEnglish (US)
Pages (from-to)295-308
Number of pages14
JournalColloids and Surfaces A: Physicochemical and Engineering Aspects
Issue number1-3
StatePublished - May 23 2002
Externally publishedYes


  • Glass-electrode
  • Hydrogen-electrode concentration cell
  • Point of zero charge
  • Potentiometric titrations
  • Rutile
  • Surface protonation

ASJC Scopus subject areas

  • Surfaces and Interfaces
  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry


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