POLAROGRAPHIC DETERMINATION OF ASCORBIC ACID IN FRUIT JUICES USING STANDARD ADDITION CALIBRATION

Abstract

Polarographic method of determination has been applied for large number of substances, both organic and inorganic. This is attributed to the simplicity, sensitivity, fast and especially when coupled with standard addition calibration, there is no need for complex and time demanding sample preparation as matrix effect can be taken care of. For example, ascorbic acid (Vitamin C) gives a well-defined oxidation in Britton-Robinson buffer which is ideal for the quantities determination over a wide concentration range. Herein, we successfully determined the concentration of ascorbic acid in orange, pink guava and tropical mango juices in Britton-Robinson buffer using standard addition calibration method. It was discovered that, the peak current values increases with increase in different concentration of ascorbic acid and straight line calibration curves were obtained. The extrapolated value from the polarographic internal standard calibration determination is in good agreement with the quoted values. The determined concentrations were 154, 165 and 143 ppm for orange, pink guava and tropical mango respectively compared to the reported value of 150 ppm on the label of each fruit juice. Ratio of ascorbic acid found to reported label values showed this polarographic method is reliable and fit-for-purpose technique for the intended analysis.