Kinetic studies on the nucleophilic cleavage of N-phthaloylglycine (NPG) in buffers of 2-methoxyethylamine, and 2-hydroxyethylamine reveal the relationship: knapp = A1 [Am]T/(1 + A2 [Am]T) where A1 and A2 are constants (kinetic parameters) and knapp and [Am]T represent apparent nucleophilic second-order rate constant and total amine buffer concentration, respectively.