L-ascorbic Acid Determination by Using Ultraviolet Spectrophotometry

Low, Kim Yeong (2011) L-ascorbic Acid Determination by Using Ultraviolet Spectrophotometry. Final Year Project (Other), Tunku Abdul Rahman University College.

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Abstract

Vitamin C is an essential water-soluble vitamin and it is the first vitamin being discovered by the Hungarian physician Professor Albert Szent-Györgyi from the adrenal cortex of cattle (Davies et al., 1991). Deficiency of vitamin C can cause scurvy. The main objective for doing this project was to perform a quantitative determination of L-ascorbic acid in supplement tablets and fruits by using ultraviolet spectrophotometer and to determine the effect of heat to the storage of vitamin C. In this project, ultraviolet spectrophotometry was chosen for the quantitative determination of L-ascorbic acid. It was found that this method can provide a fast and simple procedure for the determination of the L-ascorbic acid. The determination was done by Hitachi u-2000 UV-Vis spectrophotometer at wavelength 242.4 nm. R.S.D. less than 2.5 % and relative error less than 3.1 % for the sample tablets containing high amount of vitamin C showed that this method was more suitable for the samples containing large amount of vitamin C. Moreover, the vitamin C content of six different types of fruit juices were determined. Kiwis contained the highest concentration of vitamin C (173.58±23.57 mg/100ml and 170.70±8.63 mg/100ml for green kiwi and gold kiwi respectively) while citrus fruits came after it (Lemon-120.97±12.40 mg/100 ml, Lime-113.67±15.15 mg/100 ml, orange-96.65±12.71 mg/100 ml). The last was apple which has 67.58±6.73 mg in 100 ml of juices. In addition to that, analysis on the effect of heat showed that degradation of vitamin C is more rapid at high temperature. The reaction rate constant, k for the refrigerated sample was found to be -13.825 while for the sample stored in room temperature was found to be -26.65. In conclusion, UV spectrophotometry was more suitable for quantitative determination of samples containing high amount of vitamin C. Kiwis contained higher amount of vitamin C compared to citrus fruits and apples. Degradation rate of vitamin C was higher in the presence of heat.