Ion exchange chromatography

From Freepedia

The ion-exchange chromatography process allows the separation of ions and polar molecules based on the charge properties of the molecules.

• Stationary phase: A resin or gel matrix contains covalently bound positive or negative functional groups
  • Cation exchange column carries negatively charged groups
  • Anion exchange column carries positively charged groups
• Mobile phase: A buffered aqueous solution carries a counter-ion whose charge is opposite and in equilibrium with the total charge of the resin.

Once the charged analytes are attached to the exchange groups in the column, they must be eluted out using a buffer with a higher ionic strength or a different pH in order to weaken the electrostatic interactions between the analytes and the exchangers.

This technique separates proteins according to their net charge. For example, if a protein has a net positive charge at pH 7, then it will bind to a column of beads containing carboxylate groups (negative charge) whereas a negatively charged protein would not. material from notes of Dr. Biswas (UMDNJ).