Ionic partition diagram

There are three possibilities of letting the neutral species appear in the ionic partition diagram. Indeed, as the partition coefficient of the neutral species is neither potential- nor pH-dependent, the variable can be either the neutral species in the aqueous phase or that in the organic phase. However, to account for the experimental reality, it is more convenient to introduce the total mole number of neutral species [297], defined as ... 

This line is both potential and pH dependent, and it represents the zone where an assisted proton transfer reaction occurs. As a matter of fact, an oblique line in the ionic partition diagram always relates to such a mechanism, the slope indicating the number of protons exchanged at the interface. 

V. Gobry, F. Re5miond and H. H. Girault, Refinment of Ionic Partition Diagrams and Determination of Partition Coefficients of Multiprotic Compounds by Electrochemistry at the Interface between Two Immiscible Electrolyte Solutions, submitted. 

Reymond, F. Steyaert, G. Carrupt, P.A. Testa, B. Girault, H. Ionic partition diagrams a potential-pH representation. J. Am. Chem. Soc. 1996,118, 11,951-11,957. Tsantili-Kakoulidou, A. Panderi, I. Csizmadia, F. Darvas, F. Prediction of distribution coefficient from structure, II. Validation of prologD, an expert system. J. Pharm. Sci. 1997, 86, 1173-1179. 

Figure 173.12 Ionic partition diagram of quinidine in water/DCE interface at 21°C. (Reprinted with permission from (106). Copyright 1996 American Chemical Society).

The drawing of an ionic partition diagram requires voltammetric measurements at different pH values with equilibrated solutions. This means that a new electrochemical cell has to be prepared for each pH. Different approaches have been proposed to make the measurement more automated. One approach is based... 

Reymond, F, V. Chopineaux-Courtois, G. Steyaert, G. Bouchard, P. A. Carrupt, B. Testa, and H. H. Girault, Ionic partition diagrams of ionisable drugs pH-hpophUicity profiles, transfer mechanisms and charge effects on solvation, J Electroanal Chem, Vol. 462,(1999) p. 235. 

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