title: Colourimetric solid-phase extraction coupled with fibre optic reflectance spectroscopy for determination of ascorbic acid in pharmaceutical formulations.
abstract: A redox colourimetric solid-phase extraction (C-SPE) procedure for the determination of ascorbic acid (AA) in pharmaceutical formulations was proposed. Iron (III)-2,2'-dipyridyl (Fe(III)-Bpy) reagent solution was used as a colouring reagent for AA and the immobilization of the redox product onto Amberlite XAD-16 resin was achieved. The analyte in the sample reacted with a solid sorbent loaded with the colourimetric reagent (Fe(III)-Bpy) and then quantified directly on the sorbent surface by using a fibre optic reflectance spectrometer (FORS). The amount of AA was reflectometrically determined in a few seconds with a total sample workup and readout time of ∼10 min using only 10-ml sample volumes. The limit of detection (LOD) and quantification (LOQ) values were 0.18 and 0.6 mg L(-1), respectively, and the linear dynamic range for AA extended up to 8.8 mg L(-1). The C-SPE for different extractions (n = 5) gave a relative standard deviation (RSD) of 2.9% at 5.28 mg L(-1) AA level.
authors.affiliation: Istanbul University, Faculty of Engineering, Department of Chemistry, 34320 Avcılar, Istanbul, Turkey. filik@istanbul.edu.tr
authors.forename: Hayati
authors.initials: H
authors.lastname: Filik
authors.forename: Duygu
authors.initials: D
authors.lastname: Aksu
authors.forename: Derya
authors.initials: D
authors.lastname: Giray
authors.forename: Reşat
authors.initials: R
authors.lastname: Apak
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry; D000975:Antioxidants / Q000032:analysis*; D001205:Ascorbic Acid / Q000032:analysis*; D003124:Colorimetry / Q000379:methods*; D005336:Fiber Optic Technology; D057230:Limit of Detection; D010084:Oxidation-Reduction; D052616:Solid Phase Extraction; D013057:Spectrum Analysis / Q000379:methods*; D013997:Time Factors
chemical_list: D000975:Antioxidants; D015082:2,2'-Dipyridyl; D001205:Ascorbic Acid