The Voltammetric and Titrimetric Determination of Ascorbic Acid Levels in Tropical Fruit Samples
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Date
2009-02-09
Authors
Okiei, W. O.
Ogunlesi, M.
Azeez, L.
Obakachi, V.
Osunsanmi, M.
Nkenchor, G.
Journal Title
Journal ISSN
Volume Title
Publisher
International Journal of Electrochemical Science
Abstract
The levels of ascorbic acid in 50 tropical fruit samples were determined by titrimetric method using Nbromosuccinimide and also by cyclic voltammetry using a glassy carbon as working electrode, Ag/AgCl as reference and platinum as the auxiliary electrode in 0.1 M phosphate buffer, pH 2.0 containing 1mM Na2EDTA. The measurements were made in a potential range of 200 mV to 1000 mV in relation to reference electrode using a scan rate of 50 mV/s. The anodic peak currents for the electrochemical oxidation of ascorbic acid to dehydroascorbic acid were recorded at 580 mV. No cathodic peak current was observed in the potential range studied. Fruits found to have high levels of ascorbic acid include green pepper (182.34 mg/100g), long pepper (138.54 mg/100g), red pepper(125.59 mg/100g), tangelo (68.82 mg/100 cm3), grape (68.82 mg/100 cm3), orange (64 mg/100 cm3), lime (56.57 mg/100 cm3), pawpaw (55.8 mg/100 cm3), cherry (54.86 mg/100g), and guava (51.02 mg/100g). The results obtained by cyclic voltammetric method and titration with N-bromosuccinimide are generally comparable but large differences are obtained in some fruits. The extensive data in this report serves as a database of the vitamin C levels in fifty tropical fruits which hitherto is not available in literature. The report will serve as a guide in the selection of fruits with appreciable concentration of vitamin C
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Keywords
Vitamin C , cyclic voltammetry , tropical fruit samples , electrochemical oxidation