Chromatography Practice Test

Partition chromatography is based on the solute distributing between two immiscible liquid phases. In practice this means a liquid stationary phase paired with a separate mobile phase; how strongly the solute prefers the stationary liquid versus the mobile liquid sets how long it is retained. In reversed‑phase HPLC, the stationary phase is nonpolar (for example, C18 groups bonded to silica) and the mobile phase is polar (water with an organic modifier). The analyte partitions between the nonpolar stationary phase and the polar mobile phase, so more hydrophobic compounds spend more time on the stationary phase and elute later. This liquid–liquid distribution is what defines partition chromatography. Adsorption chromatography, by contrast, relies on the solute sticking to a solid surface. A typical example is normal‑phase silica chromatography, where polarity drives adsorption to the polar silica surface. So the correct statement captures that partition chromatography involves distribution between a liquid stationary phase and the mobile phase, with reversed‑phase HPLC illustrating this idea.