title: Photodegradation study of sodium usnate solution: influence of pH.
abstract: Photodegradation of 2.6 x 10(-5) M aqueous solutions of sodium usnate at various pH was studied. Photodegradation appeared to follow first-order kinetics and was found to be pH dependent. The degradation rate constant was calculated to be 9.20 x 10(-4) min-1, 5.93 x 10(-4) min-1, 9.69 x 10(-4) min-1, and 9.88 x 10(-4) min-1 at pH 6, pH 7, pH 8, and pH 9, respectively.
authors.affiliation: Laboratory of Industrial Pharmacy, School of Pharmacy, University of Nantes, France.
authors.forename: C
authors.initials: C
authors.lastname: Coiffard
authors.forename: L J
authors.initials: LJ
authors.lastname: Coiffard
authors.forename: Y
authors.initials: Y
authors.lastname: De Roeck-Holtzhauer
mesh_terms: D003879:Dermatologic Agents / Q000737:chemistry*; D004355:Drug Stability; D004356:Drug Storage; D006575:Heterocyclic Compounds, 3-Ring / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008027:Light / Q000009:adverse effects*; D012996:Solutions
chemical_list: D003879:Dermatologic Agents; D006575:Heterocyclic Compounds, 3-Ring; D012996:Solutions; C400715:sodium usnate