HILIC and Mixed-Mode are terms originally used to describe a specific chemical interaction or set of interactions in liquid chromatography. Recently, however, these terms have been more frequently used to describe LC columns offering retention mechanisms that vary, or are orthogonal, to a C18. These columns generally consist of a bonded phase which contains a chemical moiety other than, or in addition to, alkyl carbon chains. By incorporating double bonds, oxygen, nitrogen, or other heteroatoms, alternate retention and selectivity can be accomplished. These chemical interactions are generally not well understood or easily demonstrated, which leaves users frustrated and not using the phase to the fullest potential.

In this study we set out to explore the retention mechanisms of the PFPP stationary phase. This phase offers unique selectivity by incorporating strongly electronegative fluorine atoms on a phenyl ring. In addition to the traditional reversed-phase dispersive interactions, this phase may exhibit cation-exchange and pi-pi interactions which aid in selectivity of specific analytes. Our focus in this presentation is on method changes including temperature, mobile phase, and acid strength and concentration and how these changes affect the selectivity of target analytes. By demonstrating the influence of method changes on this phase we aim to gather a better understanding of the interactions provided by the PFPP phase and its use as a HILIC or mixed-mode phase.