Abstract The enhancement of the selectivity and sensitivity in high-performance liquid chromatography due to the presence of the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) in the mobile phase in the determination of three metal ions as complexes with sodium diethyldithiocarbamate was studied. The presence of an organic modifier such as 1-propanol in the mobile phase contributes to the decrease in the retention times of the complexes. The results show that under these conditions, the separation of the three metal ions is possible whereas in the absence of surfactant it is not possible. Also, the detection limits and selectivity are better in the presence of CTAB than in its absence. The method was applied to the determination of nickel and copper in real samples.