Optimal salt concentration can vary depending on the nature of the compound in
question. Typically, 150-250 mM works best, however you must balance the ionic and
hydrophobic nature of the compound. The lower the salt concentration, the more ionexchange
will be observed. At higher salt concentration, more hydrophobic adsorption
is observed due to salting of the protein. We typically recommend the customer
uses 50 mM potassium phosphate and 250 mM KCl at pH 6.2 as a starting point to
achieve the best results. Potassium is the preferred counter ion as it generates better
peak shape and reduces interactions with any silanols at the surface of the particle.