Methods for the Selection of Appropriate Mobile Phases

Nurok and his research group (11) proposed the use of a binary mixture of a strong and a weak solvent, because Rf can be predicted as a function of the solvent composition by the use of the following equation  

These workers used binary solvent systems over a range of mole fractions to determine, for each solute, the constants a and b of equation (8.2). For methyl and phenacyl esters, TLC was used, while overpressured layer chromatography (OPLC) was used for dansyl amino acids. Nurok and co-workers (11) also evaluated how the quality of a simulated separation varies with changing solvent strength by using the inverse distance function (IDF) or planar response function (PRF), as follows  

---