A detailed analysis of a procedure of measurement of the external mass transfer coefficients (k(f)) in RPLC systems is provided. Application is described for a system consisting of a C-18-silica monolithic column and a methanol/water eluent (70/30, v/v). The k(f) values of butylbenzene at 298 K were derived from peak profiles recorded in pulse response experiments by subtracting the contributions of the kinetic processes, i.e., axial molecular diffusion, eddy diffusion, pore and surface diffusion, from the band variance. This approach provided the Sherwood number (Sh) for a range of Reynolds number (Re) between 0.002 and 0.005 and a Schmidt number (Sc) equal to 2.7 x 10(3). The experimental values of k(f) were compared with those estimated from literature correlations, giving a relative error of ca. 11% when Pfeffer equation was used for estimating k(f). The exponents obtained for Re and Sc in Sh were 0.43 and 0.39, values comparable with those found in literature correlations, i.e., 0.33. The k(f) values estimated using the reference correlations are of the same order of magnitude as the experimental k(f) values. The acquisition of more experimental data is needed for deriving an improved correlation affording more accurate estimates of k(f) in stationary phases of cylindrical shape, like silica monoliths. (C) 2010 Elsevier Ltd. All rights reserved.