On-line redox derivatization HPLC was applied for the analysis of Fe(II) and Fe(III) cyanide complexes. The HPLC system used consisted of two C18 silica columns treated with trimethylstearylammonium chloride and a small column packed with porous graphitic carbon (PGC) placed between them. The PGC column treated with sodium sulfite completely reduced the Fe(III) cyanide complex to the Fe(II) complex, while the Fe(II) cyanide complex was converted to the Fe(III) complex by the PGC column treated with hydrogen peroxide. On the other hand, the oxidation states of the other metal cyanide complexes were not affected by PGC. Selective separations of the Fe(II) and Fe(III) cyanide complexes from the other metal complexes were demonstrated by on-line redox derivatization HPLC using the oxidized and reduced PGC column as the redox derivatization unit, respectively. The method was successfully applied for the analysis of Fe(II) cyanide complex in food grade salt.