Determination of Ascorbic Acid in Commercial Juices, on a Modified Carbon Paste Electrode, by Using a Taguchi Experiment
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Determination of Ascorbic Acid in Commercial Juices, on a Modified Carbon Paste Electrode, by Using a Taguchi Experimental Design Dolores Vázquez & Mariluz Tascón & Luis Deban
Received: 12 April 2011 / Accepted: 26 May 2011 / Published online: 5 July 2011 # Springer Science+Business Media, LLC 2011
Abstract In this paper, a simple and rapid analytical method development for ascorbic acid determination by using differential pulse voltammetry method on copper(II)phthalocyanine carbon paste electrode is shown. For this, several parameters, such as copper(II)-phthalocyanine (gram)/carbon (gram)/Nujol (millilitre) ratio, supporting electrolyte, pH and some others have been studied. In order to know the copper(II)-phthalocyanine influence on voltammetry peak height, a comparison between the analytical behaviour of a chemically modified carbon paste electrode and a conventional carbon paste electrode was carried out. The experimental conditions have been optimised by means of the experimental design using the Taguchi methodology. The catalytic oxidation peak current showed a linear depending on the ascorbic acid concentration in the range between 0.88 and 10.03 mg L−1, with the detection limit of 0.55 mg L−1. The proposed procedure was successfully applied to the determination of ascorbic acid in fruit juices without previous preparation and was compared with HPLC method applied at the same samples previously filtered. Keywords Voltammetry . Ascorbic acid determination . Copper(II)-phthalocyanine carbon paste-modified electrode . Taguchi experimental design
D. Vázquez (*) : M. Tascón : L. Deban Department of Analytical Chemistry, Faculty of Sciences, University of Valladolid, C/Prado de la Magdalena s/n, 47005 Valladolid, Spain e-mail: [email protected]
Introduction Ascorbic acid (AA) is a water-soluble substance present in a wide range of food, such as vegetables and fruits. It is also added to food as an antioxidant, for stabilisation of aroma and colour, as well as to enlarge the life of commercial products. Pharmaceuticals also often contain AA as a supplementary source in human diets. Due to this reason, many analytical procedures have been proposed for AA determination in different matrix and at several concentration levels. Its analytical determination is generally based on its reducing properties or on its capacity to produce coloured substances. Electroanalytical techniques have also been frequently used to this purpose. It is known that direct redox reaction of this specie at bare electrodes is irreversible and therefore requires high overpotentials. Moreover, the direct oxidation of AA at the bare electrode often suffers from a pronounced fouling effect, which results in rather poor selectivity and reproducibility. Therefore, many works have been reported for electrocatalytically oxidation of AA in order to overcome these problems using various chemically modified electrodes (CMEs). In these works, different modified electrodes have been used with various active mediator immobilised such as gold electrodes (
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