What happens if the solvent is too nonpolar?

What happens if the solvent is too nonpolar?

• A. Move quickly
• B. They move very slowly or not at all
• C. They precipitate
• D. They degrade

Answer: (B)

The key idea is how solvent polarity interacts with a polar stationary phase to control how far solutes travel. If the mobile phase is too nonpolar, polar solutes don’t dissolve well in it, so their attraction to the polar stationary phase dominates and they stay adsorbed there, moving very little or not at all. Nonpolar solutes will tend to migrate with the solvent, but the polar components—the ones you often want to separate—remain near the origin, giving poor separation. In short, a solvent that’s too nonpolar keeps polar compounds from moving, so they stay put or barely move.

The key idea is how solvent polarity interacts with a polar stationary phase to control how far solutes travel. If the mobile phase is too nonpolar, polar solutes don’t dissolve well in it, so their attraction to the polar stationary phase dominates and they stay adsorbed there, moving very little or not at all. Nonpolar solutes will tend to migrate with the solvent, but the polar components—the ones you often want to separate—remain near the origin, giving poor separation. In short, a solvent that’s too nonpolar keeps polar compounds from moving, so they stay put or barely move.