Kinetic and rate parameters have been estimated from the reversed-phase adsorption of three standard peptides (Angiotensin II, Bradykinin, and [D-Ala²]-Leucine Enkephalin) on C₁₈. The average particle diameters of the C₁₈ samples were 5 and 15 μm, while the pore sizes were 100 and 300 Å, respectively. The mobile phase composition was 50/50 vol.% for a binary mixture of acetonitrile and water incorporating 0.1% TFA; the particles were packed in a stainless steel column (4.6X150 mm). The experiments were performed within a linear adsorption range. The first absolute moment and second central moment were calculated from the chromatographic elution curves by performing moment analysis. The contributions of each mass-transfer step are axial dispersion, fluid-to-particle mass transfer, and intraparticle diffusion. The fluid-to-particle mass transfer coefficient was estimated by using the Wilson-Geankoplis equation. The axial dispersion coefficient and intraparticle diffusivity were determined from the slope and intercept, respectively, of a plot of H vs. 1/_uo·