If the stationary phase is polar and the mobile phase is nonpolar, what description fits the expected migration of nonpolar solutes compared to polar solutes under the same conditions?

If the stationary phase is polar and the mobile phase is nonpolar, what description fits the expected migration of nonpolar solutes compared to polar solutes under the same conditions?

• A. Nonpolar solutes migrate slower than polar solutes
• B. Polar solutes migrate at the same rate as nonpolar solutes
• C. Nonpolar solutes migrate faster than polar solutes
• D. Mobile phase polarity has no effect

Answer: (C)

In normal-phase chromatography, the retention of a solute is largely governed by how strongly it interacts with the polar stationary phase. Polar solutes form stronger interactions with that surface, such as dipole attractions or hydrogen bonding, so they are adsorbed longer and move more slowly through the column. Nonpolar solutes interact weakly with the polar stationary phase, so they spend less time adsorbed and are carried along by the nonpolar mobile phase more quickly. Under the same conditions, this means nonpolar solutes migrate faster than polar solutes.

In normal-phase chromatography, the retention of a solute is largely governed by how strongly it interacts with the polar stationary phase. Polar solutes form stronger interactions with that surface, such as dipole attractions or hydrogen bonding, so they are adsorbed longer and move more slowly through the column. Nonpolar solutes interact weakly with the polar stationary phase, so they spend less time adsorbed and are carried along by the nonpolar mobile phase more quickly. Under the same conditions, this means nonpolar solutes migrate faster than polar solutes.