title: Spectrophotometric determination of ascorbic acid with iron(III) and p-carboxyphenylfluorone in a cationic surfactant micellar medium.
abstract: A simple and highly sensitive spectrophotometric method for the determination of ascorbic acid (AA) was established by using iron(III) and p-carboxyphenylfluorone (PCPF) in a cationic surfactant micellar medium. The apparent molar absorptivity of the proposed method, which does not require an extraction procedure, was 2.05 x 10(6) dm3 mol-1 cm-1 at 655 nm. Beer's law was obeyed in the concentration range of 0.02-0.12 microgram/cm3 for AA. The procedure was successfully applied to assays of AA in pharmaceutical preparations. It is suggested that the method is based on a coupled redox-complexation reaction in which the first step is the oxidation of AA by iron(III), and the second step includes the formations of the iron(II)-PCPF (1:2) complex and the dehydroascorbic acid-iron(III)-PCPF (1:1:2) complex.
authors.affiliation: Osaka University of Pharmaceutical Sciences, Nasahara, Takatsuki, Osaka 569-1094, Japan. fujitay@oysun01.oups.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Fujita
authors.forename: I
authors.initials: I
authors.lastname: Mori
authors.forename: T
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: M
authors.initials: M
authors.lastname: Hoshino
authors.forename: Y
authors.initials: Y
authors.lastname: Shigemura
authors.forename: M
authors.initials: M
authors.lastname: Shimano
mesh_terms: D001205:Ascorbic Acid / Q000032:analysis / Q000737:chemistry*; D002138:Calibration; D002412:Cations; D004396:Coloring Agents / Q000737:chemistry* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005452:Fluoresceins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D008823:Micelles; D008956:Models, Chemical; D010084:Oxidation-Reduction; D013053:Spectrophotometry / Q000379:methods*; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: C442461:4-carboxyphenylfluorone; D002412:Cations; D004396:Coloring Agents; D005452:Fluoresceins; D008823:Micelles; D013501:Surface-Active Agents; C010159:fluorone Black; D007501:Iron; D001205:Ascorbic Acid