In normal-phase TLC, which statement best describes the stationary phase?

In normal-phase TLC, which statement best describes the stationary phase?

• A. Polar stationary phase
• B. Nonpolar stationary phase
• C. Mobile phase
• D. Inert coating

Answer: (A)

In normal-phase TLC, the stationary phase is polar. The plate is coated with a polar material (like silica gel or alumina) that presents many polar sites, such as silanol groups, which interact strongly with polar compounds through hydrogen bonding and dipole interactions. Because of these interactions, polar substances are retained longer on the plate and move more slowly, while nonpolar substances interact weakly and travel farther with the mobile phase. The mobile phase itself is typically less polar, which enhances the separation based on polarity differences. An inert coating wouldn’t provide the specific polar interactions that drive normal-phase separations, so the key feature is the polar stationary phase.

In normal-phase TLC, the stationary phase is polar. The plate is coated with a polar material (like silica gel or alumina) that presents many polar sites, such as silanol groups, which interact strongly with polar compounds through hydrogen bonding and dipole interactions. Because of these interactions, polar substances are retained longer on the plate and move more slowly, while nonpolar substances interact weakly and travel farther with the mobile phase. The mobile phase itself is typically less polar, which enhances the separation based on polarity differences. An inert coating wouldn’t provide the specific polar interactions that drive normal-phase separations, so the key feature is the polar stationary phase.