A novel reserved\|phase ion\|pair liquid chromatographic method using hexadecyltrimethylammonium bromide（HTMAB） as an ion\|pair reagent for separating the complexes of metal and 8\|hydroxyquinoline\|5\|sulphonic acid（HQS） coupled with on\|line fluorescence detection has been developed. The chromatographic behavior of metal\|HQS complexes in the proposed system was systematically investigated.When the C\-\{18\} column modified by HTMAB and the suitable mobile phase coupled with fluorescence detection（%λ%-{ex}=388 nm; %λ%-{em}=518 nm） were employed, the detection limit of cadmium is 7.72 ng/mL with an injection volume of 20 μL, and the linear range of calibration curve for cadmium is 50\800 ng/mL. It was successfully applied to determination of bio\|available cadmium in polluted soils of China. Moreover, the possible species of Cd\|HQS on the column has been investigated by log\|log plot analysis.
