We used γ-Al2O3 nanoparticles coated with sodium dodecyl sulfate–4-(2-pyridylazo)resorcinol (SDS–PAR) as an innovative sorbent for the extraction and preconcentration of trace amounts of cadmium cations. The properties of the prepared sorbent were examined by scanning electron microscopy. The effects of different parameters towards the separation and preconcentration of trace amounts of cadmium ions, such as the quantity of sorbent, the pH value, and choice of solvent for recovery of the sorbent, were investigated. Under optimum operating conditions, a cadmium ion enrichment factor of 20 was obtained using 10.0 mL of sample. The detection limit of this method for CdII cations was 0.2 ng mL–1 (n = 7) within a linear range of 0.6–340 ng mL–1 and a relative standard deviation of 1.8 % (n = 10). The method was effectively applied to the analysis of cadmium ions in food and herbal and water samples.