Spectrophotometric Determination of Vitamin C Using Indirect Oxidation with a New Organic Dye

Abstract

Background: In this study, the concentration of vitamin C was determined in various sources such as vitamins tablets, fruit juices, but particularly in natural fresh fruits e.g orange, lemon, mandarin, green lemon and lime as well as industrial juices from different companies. Methods: A simple, sensitive and accurate spectrophotometric method was developed for the determination of vitamin C in pharmaceutical preparations. The method is based on the oxidation of vitamin C by excess potassium iodate (KIO3) in acid medium and unreacted iodate reacts with an organic dye (A1) to give a yellow color and the resulting iodine is extracted with toluene and measured spectrophotometrically at 430 nm. Results: A study was performed on various important parameters of the new dye such as the volume of the dye, type of oxidizing reagents, effect of volume, effect of sulfuric acid, effect of reaction time on the bleaching and oxidation process. Calibration curves were plotted after a diluted dye solution was analyzed within an appropriate Beer's law concentration interval (3-90 µg/ml) for each dye species. Molar absorptivities were obtained with values of 12500.521 L.mol^-1.cm^-1, mean recovery rate was 98.05 %. Conclusion: The developed procedure is successful in the analysis of Ascorbic acid content in pharmaceutical formulations and natural samples. The results obtained were found to be in good agreement with certified values and standard addition procedure. The simplicity and effectiveness of this procedure to estimate pure vitamin C content with accuracy make it a useful tool in various applications.