title: Continuous variation data: 1:1 or 2:2 weak complexes?
abstract: An attempt to distinguish between 1:1 and 2: 2 weak complexes from continuous variation data is given. A modification of the Heller and Schwarzenbach's method which involves the use of the absorbance ratio y=A/A(lim) (once the limiting absorbance, A(lim) is known) may be applied to 1:1 weak complexes. This allows checking if the slope obtained is close to the theoretical value of -0.25. A curvature appears and the residuals have a pattern when a wrong 1:1 model is selected for a true 2:2 stoichiometry.
authors.affiliation: Department of Analytical Chemistry, Faculty of Pharmacy, The University of Seville, 41012 Seville, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Sayago
authors.forename: Maravillas
authors.initials: M
authors.lastname: Boccio
authors.forename: Agustin G
authors.initials: AG
authors.lastname: Asuero
mesh_terms: D004355:Drug Stability; D013053:Spectrophotometry