A new method for the determination of ascorbic acid by the kinetic spectrophotometry was established,based on the inhibitory effect of trace ascorbic acid on the reaction of Bromeosin Y with KIO4 catalyzed by Ce(Ⅳ) in the medium of H2SO4.The influence of acidity,amounts of reagents,temperature and other factors on the reaction were discussed.The optimum conditions of the reaction and some kinetic parameters were determined.The apparent energy of the catalyzed and the inhibited reaction were 35.60 kJ·mol and 69.89kJ·mol respectively.The linear range was 0.02μg·mL-1～1.6μg·mL-1 of ascorbic acid,and the detection limit was 0.011μg·mL-1.The proposed method has been applied successfully to the determination of trace ascorbic acid in various vegetables with the results corresponding to that obtained by the iodimetry.
