The formation, composition and stability of the three-component solution were investigated in details. The accuracy of the method was evaluated by comparison with the ABNT NBR 14066 standard method [26]. Acid digestion and the certified reference material (NIST SRM 1084a) were also investigated for validation. The expected advantages of the proposed procedure are the reduction of use of toxic solvents, replacement of liposoluble standards used by inorganic aqueous standards and greater stability of the analytes in the medium.