Bidentate and tridentate heterocyclic azo compounds having long alkyl chains as coating reagents for ion chromatography of manganese, zinc, and cadmium ions.

Bidentate and tridentate heterocyclic azo compounds with and without a long alkyl chain were prepared and examined for cation exchange chromatography of manganese, zinc, and cadmium; these ions could not be separated by reversed phase HPLC following precolumn derivatization with heterocyclic azo compounds owing to the dissociation of the complexes. The newly prepared azo compounds having a long alkyl chain favorably orientate in the reversed-phase stationary phase such that the coordinating parts of the ligand may make contact with metal ions in the mobile phase. Bidentate ligands showed sharp peaks but almost no resolution of manganese and cadmium. A tridentate ligand strongly retained all the three metal ions, which could be separated within 10 min by a competing ligand and by optimizing the pH.