<p>This study presented a developed magnetic dispersive micro solid phase extraction method for the preconcentration and extraction of Co(II), Ni(II), and Cd(II) ions in aqueous samples. The method employed an effective magnetic adsorbent synthesized using cobalamin (vitamin B12) as the key component, combining the benefits of magnetic separation with cobalamin’s strong affinity for heavy metal ions. The adsorbed analytes were then eluted using diluted nitric acid solution and the analytes were quantified <i>via</i> flame atomic absorption spectrometry. Several parameters that influence the efficiency of the extraction process, including adsorbent amount, complexing agent amount, pH, salt addition, vortexing time, and desorption conditions were studied and optimized. Under optimized conditions, the method achieved linear ranges of 0.5–150&#xa0;µg L^− 1 for Co(II) and Ni(II), and 0.1–150&#xa0;µg L^− 1 for Cd(II). The limits of detection were 0.20, 0.18, and 0.04&#xa0;µg L^− 1 for Co(II), Ni(II), and Cd(II) ions, respectively. The developed method demonstrated good repeatability, with relative standard deviations less than 5%. The method was effectively utilized to analyze real water and fruit juice samples, yielding good recoveries and precision. This approach offered a straightforward, sensitive, and eco-friendly alternative for determining heavy metals in complex matrices, with potential applications in environmental monitoring and food safety.</p>