Chromatographic hydrophobicity index: pH profile for polyprotic compounds.
The Chromatographic Hydrophobicity Index (CHI) has been measured for several diprotic compounds. In order to model the variation of CHI with pH, a general equation for polyprotic compounds which allows the calculation of CHI for each one of the species has been proposed. Different types of diprotic solutes have been selected: neutral acids, neutral bases, and amphiprotic compounds (non-zwitterionic and zwitterionic). The applicability of the model to these complex polyprotic compounds, its advantages and limitations, as well as the information provided by the fits is discussed. In general, the model fits the experimental behaviour of all kind of solutes very well, obtaining the higher hydrophobicity values for the neutral form of the compounds, except for the zwitterionic phenylalanine. The equation and parameters obtained allow an easy calculation of CHI of the compound at any pH value.
Departament de Química Analítica and Institut de Biomedicina (IBUB) de la Universitat de Barcelona, Universitat de Barcelona, Martí i Franquès 1-11, E-08028 Barcelona, Spain.
Elisabet
E
Fuguet
Clara
C
Ràfols
Elisabeth
E
Bosch
Martí
M
Rosés
D002853:Chromatography, Liquid / Q000379:methods; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D009930:Organic Chemicals / Q000737:chemistry*
D009930:Organic Chemicals