The phosphine oxide Cyanex 921 (tri-n-octylphosphine oxide) was found to be a very efficient extradant for gold from aurocyanide aqueous solutions. A system comprising a microcolumn packed with this new reagent was developed for the separation and enrichment of gold. Because of the high selectivity of the developed system it is possible to analyze gold in the presence of an excess of other metals and/or in high ionic strengh solutions.