ANALYTICAL CHEMISTRY DIVISION
Guidelines for potentiometric measurements in suspensions Part B. Guidelines for practical pH measurements in soil suspensions (IUPAC Recommendations 2006)
Srecko F. Oman1, M. Filomena Camões2, Kipton J. Powell3, Raj Rajagopalan4, and Petra Spitzer5
1Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, 1000 Ljubljana, Slovenia; 2Departamento de Química e Bioquímica, University of Lisbon (CECUL/DQB), Faculdade de Sciências da Universidade de Lisboa, Edificio C8, Pt-1749-016, Lisboa, Portugal; 3Department of Chemistry, University of Canterbury, Christchurch, New Zealand; 4Department of Chemical and Biomolecular Engineering, National University of Singapore, 117576, The Republic of Singapore; 5Physikalisch-Technische Bundesanstalt (PTB), Postfach 3345, D-38023, Braunschweig, Germany
Abstract: The measured cell potentials for suspension potentiometric
cells have been interpreted and explained by a detailed analysis of the
schemes for these cells ["Guidelines for potentiometric measurements in
suspensions. Part A. The suspension effect (IUPAC Technical Report", Pure
Appl. Chem. 79, 67 (2007)].
Some former disagreements amongst investigations have been clarified. A
new unambiguous operational definition of the suspension effect (SE) is
presented. It is defined as the difference in cell potential for two suspension
potentiometric cells, one with both electrodes in the separated equilibrium
solution (eqs) and the other with both electrodes in the sediment or suspension.
This potential difference is the sum of the change in the indicator electrode
(IE) potential and the change in the liquid junction potential of the reference
electrode (RE), when the electrodes are used for measurement, once in the
sediment of the suspension and then in its eqs.
Keywords: operational definition of suspension effect; suspension effect; pH; suspension potentiometric cell; IUPAC Analytical Chemistry Division; pIon; boundary potential; mixed potential; soil pH; anomalous liquid junction potential.
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