In gold mining, there is a tendency to switch from cyanide leaching to the much less toxic thiosulfate leaching process. Thiosulfate leaching is a sensitive process that requires more optimization of the components of the leach reaction to maximize gold recovery and reagent loss. Sulfite, thiosulfate, thiocyanate, and tetrathionate are separated on a Metrosep A Supp 5 - 250/4.0 column. Perchlorate is choosen as an eluent as most of the metal perchlorates are soluble in water. This avoids metal precipitation in the IC System.