Abstract − Analytical Sciences, 16(5), 487 (2000).
An Automatic Spectrophotometric Titration Procedure forAscorbic Acid Determination in Fruit Juices and SoftDrinks Based on Volumetric Fraction Variation
Ana Paula S. PAIM and Boaventura F. REIS
entro de Energia Nuclear na Agricultura, Universidade de Sao Paulo, PO Box 96,13400-970 Piracicaba-SP, Brazil
A spectrophotometric flow titration procedure for ascorbic acid in fruit juices and soft drinks based on volumetric fractionvariation employing a reaction with 2,6-dichloroindophenol is described. A flow network was designed to implement themulticommutation process and a set of microcomputer controlled three-way solenoid valves was employed to handle theinsertion of the titrand and titrant solutions into the analytical path. All the steps involved in the titration procedure werecarried out automatically without any operator assistance. Fruit juices and soft drinks could be analyzed without anyprior chemical treatment. Accuracy was assessed by comparing results with those obtained by the reference method(AOAC). No significant differences at 95% confidence level were observed. Other profitable features were achievedsuch as a percentual standard deviation of results of 1.1% (n = 5) for a typical juice sample containing 1.2 mmol L-1ascorbic acid, a low sample consumption (6 uL per run), and an analytical throughput ranging from 5 to 30determinations per hour for sample concentrations ranging from 0.6 to 6.0 mmol L-1.
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