Kinetics of interaction of histidine and histidine methyl ester with ninhydrin in micellar media

Kinetics of the interaction of histidine and histidine methyl ester with ni nhydrin under varying concentrations of reactants, anionic (sodium dodecyl sulphate, SDS), cationic (cetyltrimethylammonium bromide, CTAB) and non-ion ic (Triton X-100, TX-100) micelles have been carried out. Rate of the react ion was found to be independent of the initial concentration of histidine l and histidine methyl ester) but was dependent on [Ninhydrin]. The SDS micel les had no effect on the rate of the reaction. In the presence of the CTAB micelles a small enhancement in the rate was observed. The rate - [CTAB] pr ofile showed that the increase in [CTAB] increased the rate up to a maximum value and a further increase had a decreasing effect on the rate. The rate was enhanced by TX-100 also but, unlike CTAB micelles, TX-100 possessed a curve without peak for the rate - [TX-100] profile. The following rate equa tion was obeyed by the reaction in CTAB and TX-100 micelles: k(Psi) = k(w)[N](T) + (k(m)K(s) - k(w)) [D-n].M-n(s)/1 + K-s[D-n] Values of k(w), k(m), and k(s) were evaluated and are reported herein. (C) 1999 John Wiley & Sons, Inc.