Reversed-Phase Ion Pair Chromatography RP-IPC

Ion pair chromatography (IPC) typically uses a reversed-phase column in conjunction with a special type of chemical in the mobile phase called an ion-pairing reagent. Reversed phase essentially means that the column s stationary phase is nonpolar (less polar, more organic) than the mobile-phase solvents. For RP-IPC, the stationary phase is a carbon chain, most often consisting of 8 or 18 carbon atoms (C8, C18) bonded to a silica support. The mobile-phase solvents usually consist of water mixed with a water-miscible organic solvent, such as acetonitrile or methanol. 

The ion-pairing reagent is a compound that has both an organic and an ionic end. To promote ionic interaction, the ionic end should have a charge opposite to that of the analytes of interest. For anionic IPC, a commonly used ion-pairing reagent is tetrabutylammonium hydroxide (TBAOH) for cationic IPC, hexanesulfonic acid (HSA) is often chosen. In principle, the ionized/ionizable analytes interact with the 

FIGURE 18.4 Principle of ion pair chromatography (anionic mode). 

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