Analytical applications of catalytic properties of modified cyclodextrins

This paper describes the evaluation of the catalytic properties of modified cyclodextrins for analytical applications. The beta-dimethylcyclodextrin was modified by adding one and two imidazolyl groups at carbon three positions. The modifications produced enhancements of catalytic activity for the hydrolysis of p-nitrophenyl acetate at neutral pH by factors of 1000 or more relative to the unmodified cyclodextrins. The catalytic properties of the monosubstituted cyclodextrin were evaluated for the quantification of p-nitrophenyl acetate in the concentration range of 10-90 mumol/L. Results obtained by equilibrium, initial-rate, and error-compensating predictive kinetic methods were compared. The equilibrium and predictive kinetic options yielded virtually identical results, with linear changes with concentration throughout the range studied and severalfold larger than the initial-rate option and dependencies on temperature, pH, and catalyst concentration that are 5-10-fold smaller than the initial-rate option.