Determination of phenolic compounds and ascorbic acid in different fractions of tomato by capillary electrophoresis with electrochemical detection

Tomato (Lycopersicon esculentum Mill.), one of the most important crops worldwide, contains different classes of substances with antioxidant properties such as carotenoids, vitamin C, and phenolics. A method based on capillary electrophoresis with electrochemical detection has been developed to analyze ascorbic acid and phenolics in the peel, pulp, and seeds of tomatoes. Operating in a wall-jet configuration, a 300 & micro;m diameter carbon disk electrode was used as the working electrode, which exhibits a good response at +0.90 V (vs saturated calomel electrode) for the analytes. Under optimum conditions, the analytes were baseline separated within 20 min in a 50 mmol/L borate buffer (pH 8.7). Notably, excellent linearity was obtained over 3 orders of magnitude with detection limits (S/N = 3) ranging from 1 x 10(-8) to 2 x 10(-7) g/mL for all analytes. This proposed method has been successfully applied to monitor the content of ascorbic acid and phenolics in real samples, and the assay results were satisfactory.