title: Determination of dissociation constants of some pharmaceutical compounds using derivative spectrophotometry.
abstract: Derivative spectrophotometry is applied to the determination of the dissociation constants (pKa) of some weakly dissociating compounds. The pKa value(s) can be calculated by measuring the amplitude of derivative maxima (D) at the selected wavelengths for the dissociated, undissociated and partially dissociated forms of the compound. A graphical technique, based on plotting the derivative spectrophotometric titration curves and interpolating pKa at D1/2 is also presented. Both methods are applied to pharmaceutical compounds with single and double dissociation constants. The results are in good agreement with the reported pKa values of the investigated compounds.
authors.affiliation: Pharmaceutical Analytical Chemistry Department, Faculty of Pharmacy, University of Alexandria, Egypt.
authors.forename: I I
authors.initials: II
authors.lastname: Hewala
authors.forename: F A
authors.initials: FA
authors.lastname: el-Yazbi
authors.forename: A
authors.initials: A
authors.lastname: Awad
authors.forename: A M
authors.initials: AM
authors.lastname: Wahbi
mesh_terms: D002626:Chemistry, Pharmaceutical / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D004364:Pharmaceutical Preparations / Q000737:chemistry*; D013053:Spectrophotometry / Q000379:methods; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D004364:Pharmaceutical Preparations