Study of complex formation between 18-crown-6 and Pb2+, Tl+, and Cd2+ cations in binary aqueous-nonaqueous solvents using differential pulse and square-wave polarography

Complex formation of Pb2+, Tl+, and Cd2+ cations with 18-crown-6 was studie d in water-propanol, water-acetonitrile, and water-dimethylformamide binary systems at 20 degreesC using square-wave polarography and differential pul se polarography. In all cases, 1:1 complexes were formed. The formation con stants of the complexes increased with increasing concentration of nonaqueo us solvent and in the series of cations Cd2+ < Tl+ < Pb2+. In general, the stabilities of inidividual complexes were found to decrease as the binary s olvent mixture varied from water-acetonitrile to water-propanol and to wate r-dimethylformamide.