Ion Pair Reagents: Partitioning into Non-Polar Phases

[CrimpJiggler]

I'm reading about ion chromatography at the moment and read that one method is to use an ion-pair reagent which pairs with the ionic analyte, forming a neutral compound which can then partition into the non polar stationary phase. If an anionic analyte pairs with a cationic ion-pair reagent to form a salt, how would it be any more likely to partition into the non polar stationary phase? Salts are still ions. For this to work, does the analyte have to form a covalent compound with the ion-pairing reagent or at least a salt which is insoluble in the mobile phase?

 

[jbsteele]

An ion-pair reagent will form a neutral compound with the ionic analyte, which can then partition into the non-polar stationary phase. The neutral compound formed by the ion-pair reagent and the analyte can be either a covalent bond or an ionic salt, depending on the nature of the analyte and the ion-pair reagent. Covalent bonds are preferred because they are more likely to stay in the non-polar stationary phase, while ionic salts may have a tendency to dissolve in the mobile phase and not partition into the stationary phase. Therefore, it is preferable for the ion-pair reagent and analyte to form a covalent bond or an insoluble salt if possible.