Diatoms (microscopic algae) are regarded as useful tracers in catchment hydrology. However, diatom analysis is labour-intensive; therefore, only a limited number of samples can be analysed. To reduce this number, we explored the potential for a time-integrated mass-flux sampler to provide a representative sample of the diatom assemblage for a whole storm run-off event. Our results indicate that the Phillips sampler did indeed sample representative communities during two of the three events.