Rapid spectrophotometric determination of ascorbic acid in citrus fruits

A new spectrophotometric method has been developed for determining ascorbic acid in citrus fruits. The method is based on interaction between dimethoxydiquinone and ascorbic acid, followed by extraction with chloroform. The resulting chloroform solution gives a maximum absorption at 530 nm, a determination limit of 22.0 microng/ml, and a linear range from 22.0 to 97.5 microng/ml. The molar absorptivity of the chloroform solution was 1.62 x 10(3). The reaction was quantitative over the pH range from 3.0 to 7.0. Ascorbic acid in citrus fruits was successfully determined by this method. Comparison of results with those obtained by using the AOAC method showed excellent agreement; the average recovery for the analysis of orange, grapefruit, and lemon juices was 100 +/- 0.3%.