study of protonation equilibrium of lorazepam by potentiometry and multiwavelengths spectrophotometry

the acid-base equilibrium of lorazepam was studied by means of potentiometry andmultiwavelengths spectrophotometry. the stoichiometric equilibrium constants were determinedat 25 °c and constant ionic strength 0.1 mol l-1 (nacl). the acidity constants pk1=1.58±0.05and pk2=11.67±0.07 were found by potentiometry, and pk1=1.54±0.02 and pk2=11.61±0.03 bymulti-wavelengths spectrophotometry. potentiometric determination of equilibrium constantswas performed by application of the formation function method. data analysis program appliedfor multi-wavelengths spectrophotometric determination of acidity constants.