A differential receptor for selective and quantitative multi-ion analysis for Co2+ and Ni2+/Cu2+

The differential mode of complexation of chromogenic sensor 3 with Co2+ versus Ni2+ (or Cu2+) at pH 4.0 in water leads to new absorption bands at λmax 620 nm in the case of Co2+, at λmax 380 and 460 nm for Ni2+ and at λmax 460 nm for Cu2+. These differential responses allow sensor 3 to be used for the selective and quantitative estimation of Co2+ and Ni2+ or Co2+ and Cu2+ from their mixtures.