Interaction of ninhydrin with zinc(II) complex of tryptophan in the three dicationic gemini surfactants
Interaction of ninhydrin with zinc(II) complex of tryptophan in the three dicationic gemini surfactants
Present work concerns with the interaction of ninhydrin with zinc(II) complex of tryptophan ([Zn(II)-Trp]+) in the three dicationic gemini surfactant systems. To record critical micellar concentration (CMC) and absorbance, we have used Systronics conductivity meter and UV-visible spectrophotometer, respectively. Experiment opens up the fractional- and first-order paths in ninhydrin and complex, respectively. Gemini micellar medium is found more superior over aqueous medium. Rate constant (kψ) vs. [gemini] plot shows the unusual role of geminis on kψ. kψ increases with gemini concentration (at concentrations lower than the CMC, part I) and leveling-off regions obtain (concentration up to 400 × 10−5 mol dm−3, part II). Characteristics of part I and part II are just the same as that of conventional surfactant. Later, gemini produces a third region of increasing kψ at higher concentrations ([gemini] > 400 × 10−5 mol dm−3, part III). Detail and systematic elucidation about the effect of surfactants are mentioned and discussed in the text. Binding constants (KS for [Zn(II)-Trp]+ and KN for ninhydrin) and rate constant (km in geminis) were determined by nonlinear least squares regression technique. The kinetic results acquired can reasonably be interpreted by pseudo-phase model of surfactant micelles.