Metal catalyst used in the production of single-walled carbon nanotubes (SWNTs) can be effectively removedfrom the as-grown nanotubes by an in situ chelation/supercritical fluid carbon dioxide extraction method. Apretreatment procedure using bulk electrolysis with ethylenediaminetetraacetic acid significantly improvesthe efficiency of supercritical fluid extraction probably by removing the amorphous carbon associated withthe metal from the SWNTs. More than 98% of the iron impurity can be removed from the as-grown SWNTsusing this two-step purification method without obvious damage to the nanotube structures according to ourspectroscopic data.