Determination of citric acid in soft drinks using flow injection with potentiometric detection |
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| Authors: | José L F C Lima C Delerue-Matos M Carmo M C V F Vaz and Jeanine Silva |
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| Institution: | (1) CEQUP/Departamento de Química-Física, Faculdade de Farmácia (U.P.), Rua Aníbal Cunha 164, P-4050 Porto, Portugal, PT;(2) Instituto Superior de Engenharia do Porto, Rua S. Tomé, P-4200 Porto, Portugal, PT |
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| Abstract: | A flow injection analysis (FIA) system with potentiometric detection has been developed for the determination of citric acid
in commercial fruit juices using a copper-selective tubular electrode. It consists of the complexation of citrate ion with
copper (II) ion, monitoring the free copper (II) concentration. Linear relationships between the potential and log concentrations
of citric acid in the range of 1 × 10–3 mol/L – 1 × 10–2 mol/L were attained with samples injected in the system without prior treatment. Repeatability was determined by assessing
the relative standard deviation for ten replicate injections of different juice samples which varied from 1.2% to 3.0%. The
results provided by the automated system were compared with those of an enzymatic conventional method used for the analysis
of citric acid in food and a relative deviation of less than 4.0% was found. Recovery trials resulted in values from 97.0%
to 101.0%. The system allows a sampling frequency of 60 samples/h.
Received: 22 October 1998 / Revised: 14 December 1998 / Accepted: 16 December 1998 |
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