Figure 2: Absorbance vs. time graphs for the reaction of betahistine dihydrochloride and NBD-Cl, at fixed concentration of NBD-Cl and different concentration of betahistine dihydrochloride: (1) 1.19 x 10-6 ; (2) 2.39 x 10-6 ; (3) 4.78 x 10-6 ; (4) 9.56 x 10-6; (5) 1.43 x 10-5; (6) 1.91 x 10-5; (7) 2.39 x 10-5; (8) 2.87 x 10-5; (9) 3.35 x 10-5M of the studied drug.