The mass transfer zone (MTZ) method using the linear driving force (LDF) approximation is the most common and frequently used technique for the analysis of adsorption kinetics from a fixed-bed breakthrough curve and for adsorptive process design. However, the adsorption kinetics obtained by the MTZ method includes approximations and estimation errors. This report describes a new analytical method for determining the intraparticle diffusivity (D-S) and the fluid-film mass transfer coefficient (k(F)) from an experimental breakthrough curve without using the LDF approximation and empirical correlations for estimating k(F). The proposed method has the advantage of less trial and error on the curve-fitting process and helps better determine DS and k(F). The estimation procedure of the Biot number that represents the ratio of DS to kF is the key of this method. The values of DS and k(F) for the adsorption of phenols onto activated carbon were determined from experimental breakthrough curves using the new analytical method. The results indicate that the method presented in this study yields reliable values.