Heterogeneous systems often show complex kinetic behaviour attributed to the presence of a distribution of rate constants which reflects the distribution of particle sizes in the system. The characterisation of this distribution from the experimental data is not straightforward. Existing techniques for the analysis of dynamic light scattering data, where a similar problem arises, can be used to analyse the data from dispersed kinetics. This unified approach is applied to the analysis of both kinetic and dynamic light scattering data for polydisperse colloidal systems. Together with two techniques, cumulant analysis and CONTIN, an improved log normal particle size model is introduced. The power of the model is assessed by comparison with a model-free approach studying the kinetics of interfacial electron transfer from TiO₂ colloids to methyl viologen in solution.