Determination of metal cyanide complexes in gold processing solutions by capillary electrophoresis

A capillary electrophoresis method to determine metal cyanide complexes and sulphur compounds in gold processing solutions using direct UV absorbance detection has been developed. The method is based on the use of electroosmotic flow modifiers, such as C17H38NBr, to control the separation and in the on-column concentration of the sample by using the stacking effect to increase the sensitivity. By optimizing the analytical conditions, analysis times of less than 15 min and detection limits of metals in the mid-ppb range have been obtained with good resolution. The quantitation and determination of the metal cyanide complexes Au(CN)(2)(-), Ag(CN)(2)(-), Cu(CN)(3)(2-), Ni(CN)(4)(2-) and Fe(CN)(6)(4-), HS- and SCN-, present in samples from the leaching of a gold mineral (Minas Gerais, Brazil) and a gold sand (Itenez, Bolivia) by using a sodium cyanide (NaCN) solution (1000 ppm and pH 10.5 adjusted with CaO, as in real processes), has been achieved. Finally, the evolution of the formation within the time of gold cyanide complexes under leaching conditions has been studied by using the analytical method proposed.