A simple and selective method based on a sodium dodecyl sulfate (SDS)–coated chromosorb P modified by 2‐mercaptobenzoxazole (MBO) has been developed to selectively separate and concentrate ultra trace amounts of mercury(II) ions for its highly sensitive measurement by cold vapor atomic absorption spectrometry (CVAAS). The mercury ions were adsorbed quantitatively on SDS‐coated chromosorb due to its complexation with MBO, while the retained Hg²⁺ ions were then stripped from the column with minimal amounts of 2 M nitric acid in acetone. The eluting solution was sent to CV‐AAS for evaluating Hg²⁺ ion content and results indicate that the calibration curve was linear for Hg²⁺ ion in the range of 0.05–85.6 ng mL⁻¹ and 0.09–9.6 µg mL⁻¹ of Hg²⁺ ions. Maximum capacity of the SDS‐coated chromosorb modified with 40 mg of the ligand was found to be 498±30 µg of mercury(II), the limit of detection was 0.01 ng mL⁻¹, and enrichment factors were about 300, which make it suitable it for dilute solution analysis. The method was successfully applied to the determination of Hg²⁺ ion content in real samples.