What properties of the compounds should I consider when selecting an ion exchange chromatography?

The properties of compounds one should consider when selecting an ion exchange chromatography include: the isoelectric point (pI), media particle size, media porosity, and the ionic form of media. For compounds that can be positively or negatively charged depending on the pH, the pI determines the separation strategy. Above the pI, the compound is negatively charged and anion exchange support is used. Below the pI, the compound is positively charged and cation exchange support is used. The choice of exchanger also depends on its stability over the functioning pH range. High porosity supports are suitable for large molecules like proteins, while low porosity supports are better for separating smaller molecules like inorganic ions. Particle size affects resolution and flow rates. Smaller particles offer higher resolution but require lower flow rates, while larger particles allow higher flow rates but yield lower resolution. Ion exchange media come in different ionic forms, and the choice depends on the selectivity of the sample ion. The counterion currently adsorbed onto the support's functional groups should have lower selectivity than the sample ion to facilitate its adsorption onto the support.