Factor analysis applied to the study of retention mechanism of nitroanilines in normal phase high performance liquid chromatography Original Research Article

The mathematical techniques of abstract factor analysis (AFA) and target factor analysis (TFA) were used to study the role of molecular interactions on the retention mechanism of nitroanilines in normal phase high performance liquid chromatography. The two factors that were found responsible of the retention, are the solvent hydrogen-bond basicity, as measured by Kamlet and Taft’s β parameter, and unity. The unity target vector takes into account the chemical nature of each solute, this nature being a constant contribution in all data referring to each solute. It is proposed that the solvent interacts with the silanols groups on the silica surface and it can be displaced by the solute if this has stronger tendency to form hydrogen bond than the solvent. On the other hand, cluster analysis allowed us to group compounds as a function of the specific interactions involved. The studies emphasized the predictive power of this type of analysis in retention behavior. Moreover, it is shown that the behavior of nitroanilines in normal phase HPLC over silica can be explained based on the solvent–solute effects obtained by UV–Visible spectroscopy.