Heavy metals are essential raw materials for the manufacture of industrial products, but they are one of the causes of environmental pollution and are harmful to human health. Due to their toxicity, the presence of heavy metals in water and food is strictly regulated. Graphite furnace atomic absorption spectrophotometry (GFAAS) is a widely used technique for heavy metal analysis because of the small sample volume required and a simple operating procedure involved. However, sensitivity at trace concentrations of analyte in the matrix is limited by physical and chemical interferences. Overcoming this limitation requires the preconcentration and separation of analytes.

In this study, a solid-phase extraction (SPE) method using activated carbon modified with stearic acid (SA-CAA) as an adsorbent was developed to preconcentrate cadmium and nickel ions in water samples. Different characterization methods were employed to confirm the structural and surface modifications of the studied absorbent. The results show that the stearic acid modification of activated carbon enhanced the interaction between the adsorbent and heavy metal ions, leading to an approximately twofold increase in recovery compared to unmodified activated carbon. The analytical parameters affecting recovery, including the adsorption time, amount of adsorbent, initial pH of the sample solution, desorbent conditions, and sample volume, were optimized. The analytical performance of the proposed method, such as the calibration curve, analytical precision, detection limit, and tolerance to interfering components, was evaluated.