Kinetics of the interaction of ninhydrin with the [Ni(II)-histidine](+) complex in water and surfactant micelles

Kinetics of the condensation reaction of ninhydrin and the [Ni(II)-histidin e](+) complex has been studied spectrophotometrically at pH 5.0, both in aq ueous and aqueous-cationic micelles of cetyltrimethylammonium bromide (CTAB ). The same product was obtained in both the media. The results obtained in the micellar medium are treated quantitatively in terms of the kinetic pse udo-phase and Piszkiewicz models. The rate constants. binding constants wit h the micelles, and the index of cooperativity have been evaluated. On the basis of observed data a possible mechanism has been proposed. The same pro duct was obtained in nonionic micelles of TX-100, but the studies were hamp ered due to the appearance of turbidity, whereas anionic micelles of sodium dodecyl sulphate did not catalyze the reaction. (C) 1999 John Wiley & Sons , Inc.