In this work, the adsorption of a polyclonal antibody (IgG) on a preparative strong cation exchanger is described in detail. In a first stage, the polyclonal mixture is characterized using both chromatographic and non-chromatography methods. This analysis suggested that the mixture can be simplified by lumping the different components of the IgG into two "macro-components", referred to as pseudo-variants in the following. An analytical method for the determination of the concentrations of the two pseudo-variants is developed. Based on this, the mass transport and the adsorption isotherm parameters are determined experimentally using only well known sort-cut methods. This analysis is evidencing the complexity of the characterization when operating in the presence of slow diffusing mixtures of components. Even in the presence of strong competition, mass transport plays a major role in determining the peak shape. In frontal analysis, competition is still operative after full saturation of the column.