The use of a cyclodextrin polycondensate or a composition comprising at least one cyclodextrin polycondensate, as an agent for capturing at least one substance chosen from a metal element and an organic molecule having an octanol/water partition coefficient, referred to as Log Kow, greater than or equal to 2, the cyclodextrin polycondensate being obtained by reacting the following compounds (A) to (C): (A) at least one cyclodextrin, (B) at least one linear, branched or cyclic polycarboxylic acid, that is saturated, unsaturated or aromatic, and (C) at least one ethylene vinyl alcohol copolymer (EVOH).