Cu2+- and Cd2+-buffers in water—ethanol media

The complex formation of Cu2+, Cd2+, Mg2+ ions with the iminodiacetic anion (L2−) is studied in water—ethanol media (70% by mass), I = 0.01 M (LiNO3) by potentiometry methods (pH, pCd, pCu). The stability constants of the complexes CuL, CuL2−2, CuHL+, CuOHL−, CdL, CdL2−2, CdL4−3, Cd2L2, MgL, CdMgL2 are determined. These results are used for the preparation of Cu2+- and Cd2+-buffer solutions with 8.5 < pCu < 12.1 and 5.7 < pCd < 8.9 in water—ethanol media. Experimental and calculated on the base of stability constants pM values are in a good agreement. It is shown, that the iminodiacetic anions have no specific influence on the membranes of Cu2+- and Cd2+-selective electrodes in water—ethanol media.