AbstractThe effect of solute retention is investigated for two hydride‐based stationary phases: bidentate C18 and cholesterol. Several small molecules and peptides are used as solutes. In the reversed‐phase mode, most compounds have the expected temperature behavior, i. e. decreasing retention with increasing temperature. Two analogs of the drug lisinopril do exhibit the opposite behavior on the cholesterol column; increasing retention with increasing temperature. In the aqueous normal phase (ANP) mode, more compounds, particularly certain peptides, have this unusual retention behavior with respect to temperature. These preliminary studies indicate that as ANP retention becomes stronger, there is a greater possibility of observing increasing retention with increasing temperature.