Complexometric determination of copper(II) in ores, alloys and complexes using 2-mercaptoethanol as indirect masking reagent

A complexo-titrimetric method for the determination of Cu(II) in the presence of other metal ions is described, based on the selective masking ability of 2-mercaptoethanol towards Cu(II). Copper and other ions in a given sample solution are initially complexed with an excess of EDTA and the surplus EDTA is titrated with zinc sulphate solution at pH 5.0-6.0 (hexamine), using xylenol orange as indicator. A known excess of 2-mercaptoethanol solution (10%) is then added, the mixture is shaken well and the released EDTA from the Cu-EDTA complex is titrated against standard zinc sulphate solution. The interferences of various ions are studied and the method is applied to the determination of Cu in its ores, alloys and complexes. Reproducible and accurate results are obtained for 2.5-40 mg or Cu with relative errors < =0.4% and standard deviations < =0.04 mg.