The invention concerns a method for separating at least one catalyst or adsorbent from a homogeneous mixture of catalysts or adsorbents, said catalysts or adsorbents having been used in a method for treating gas or hydrocarbon feedstock, said method involving separating the grains of catalysts or adsorbents depending on a sorting threshold corresponding to a content of the constituent element of interest defined by the operator. The grains of catalysts or of adsorbents pass in front of the LIBS detection system, which detects the presence of said element of interest according to the wavelength(s) characterising said element, the analyser associated with the LIBS processes the signal sent by the detector by comparing same with a setpoint value representing the sorting threshold and sends a signal to a means for discharging the catalyst grains in such a way as to separate said grains from the other catalysts and/or adsorbents of said mixture. At least one of the batches of catalysts with a low concentration of
