The measurement of acetonitrile and methanol adsorption was carried out on stationary phases with specific functionalities. The results were compared with the adsorption of those solvents on alkyl-modified adsorbents. This comparison allows us to describe the effect of polar groups on the adsorption of the organic modifiers. Our results clearly demonstrate how the functional groups modify the chromatographic properties of the homogeneous hydrophobic adsorbents. (c) 2008 Elsevier B.V. All rights reserved.