Practice question

Ion exchange chromatography separates ions or charged biomolecules using oppositely charged matrices. A cation exchanger must bind positively charged analytes, therefore matrix carries negatively charged functional groups such as carboxymethyl or sulfopropyl residues. These anionic groups electrostatically attract cations from mobile phase while repelling anions. Elution is achieved by increasing salt concentration or changing pH to compete for binding. Conversely, anion exchangers bear positive groups like diethylaminoethyl. Selecting negatively charged matrix for cation separation is crucial for protein purification based on isoelectric point and surface charge distribution at operational pH.