In contrast, Cu(CN)32− is relatively stable with much higher tolerance to a solution chemistry change. Therefore, CN/Cu = 3/1 and a cyanide concentration of 10 ppm (equals to 0.3846 mM) were used for the present flotation study. To avoid the interference of free cyanide and its loss by HCN volatilisation resulting in the change of cyanide speciation, pH value was modified to 10 in flotation pulp. At this pH, the CN- concentration was lower than 0.5 ppm which was proved previously to have a negligible effect on the flotation performance of the same ore (Guo et al., 2013). The effect of cyanide concentration on copper cyanide speciation was presented in Fig. 4, showing Cu(CN)32− as the dominant species over a wide range of cyanide concentration. This implies that higher signal to noise ratio could be obtained using higher cyanide concentrations in electrochemical studies without changing cyanide speciation. It was also calculated from Visual MINTEQ that the copper cyanide speciation at CN/Cu = 3/1 showed no change in the presence of sodium borate (Na2B4O7) which was used as pH buffer for the electrochemical studies.