COLORIMETRIC DETERMINATION OF ANTIOXIDANT VITAMINS E AND C

Abstract

Determination of vitamin E (Tocopherol) and vitamin C (Ascorbic acid) by reduction ferric to ferrous ion, which was determined through reaction with potassium dichromate in acidic media using visible spectrophotometry was investigated in this research. The method was based on the use of sodium nitro prusside as a newly reagent source for ferric ion. The colour solution gave a maximum absorption at 564.4 nm, which was applied to the determination method. Conditions optimization was conducted through study different parameter such as volume of reagent, time, acid volume, temperature. The obtained results revealed that the value of R2 was (0.99991) for both vitamins, detection limit (0.10 and 0.07), the quantitative limit (0. 33 and 0.21), the linear ranges (0.5 – 30 and 0.25 – 50) μg / mL, R.S.D (2.88 and 1.62) for vitamin E and C respectively. Results showed that the newly developed methods could be applied to determine vitamin E and C in their pure state and in pharmaceuticals with high accuracy and low cost without need any complicated treatments. Method accuracy was validated by recovery percentage mean (100.02 and 99.92 %) for vitamin C and E respectively.