Fluorescence Properties of Metal Complexes of 8-Hydroxyquinoline-5-sulfonic Acid and Chromatographic Applications

Seventy-eight metal species are examined for fluorescence properties of their chelates with 8-hydroxyquinoline-5-sutfonic acid (HQS); 42 of these fluoresce, many intensely. The optimum pH, determined by ligand ionization vs. hydroxo compiex formation, iles between 5 and 8. Cadmlum forms the most fluorescent complex In a purely aqueous solution. Fluorescence Is enhanced for many metals in surfactant (hexadecyltrlmethyiammonlum ion, HTA') containing media and in a water:dimethytformamide solvent. A number of metal ions quench the fluorescence of other metal-HQS chelates, Fe( I I1) being by far the most effective, and such quenching is accentuated in media contalnlng HTA'. The fluorescence propertles can be exploited by introducing the ligand through a postcolumn reactor or by Incorporating it in the eluent in a chromatographic system. Subpicomole detection limits are attainable for Cd, Mg, and Zn.