Which statement about ion-exchange chromatography is true?

Which statement about ion-exchange chromatography is true?

• A. The resin phase is soluble in water and separation is based on solubility.
• B. The resin phase is insoluble in water and separation is based on ionic charge.
• C. It separates based on molecular weight.
• D. It separates based on hydrophobicity.

Answer: (B)

Ion-exchange chromatography relies on fixed charged groups attached to a solid, water-insoluble resin. As the sample flows through, ions in solution exchange with ions on the resin, so separation depends on how strongly each ion interacts with those charged sites. The resin must stay in place and remain insoluble in water to provide a true stationary phase, which is why the mechanism is described as separation by ionic charge. This is not about solubility of the resin, molecular weight, or hydrophobicity. Other methods separate by size (molecular weight) or by hydrophobic interactions, whereas ion-exchange uses electrostatic attraction and selective binding that can be adjusted with pH or salt to elute the bound species.

Ion-exchange chromatography relies on fixed charged groups attached to a solid, water-insoluble resin. As the sample flows through, ions in solution exchange with ions on the resin, so separation depends on how strongly each ion interacts with those charged sites. The resin must stay in place and remain insoluble in water to provide a true stationary phase, which is why the mechanism is described as separation by ionic charge. This is not about solubility of the resin, molecular weight, or hydrophobicity. Other methods separate by size (molecular weight) or by hydrophobic interactions, whereas ion-exchange uses electrostatic attraction and selective binding that can be adjusted with pH or salt to elute the bound species.