Method Development and Validation for Spectrophotometric Determination of Ascorbic Acid in M. stenopetala Leaves Through Catalytic Titration with Hexavalent Chromium

摘要

M. stenopetala has gained attention recently in Ethiopia due to its multiple uses. It is a drought tolerant fast growing indigenous tree mainly planted and maintained for its nutritional value. An ascorbic acid excess can lead to gastric irritation and the metabolic product of vitamin C (oxalic acid) can cause renal problems. Thus, its level in food stuffs should be monitored. Hence, in this project, it was aimed to develop a novel spectrophotometer method for determination of ascorbic acid content in M. Stenopetala through Catalytic titration with Hexavalent chromium. The developed method was validated against HPLC as standard technique. Cr (VI) was used as UV-active material and Mn (II) used as catalyst. Determination of AA was based on the decrease in absorbance of the Cr (VI) solution as a result of its reaction with AA. Factors influencing the reduction of Cr (VI), including incubation time, solution pH and background concentration ratio had been optimized. The theoretical detection limit and Limit of quantification were calculated to be 0.00154 and 0.005134 mg/ml, respectively. Out of the 3 different area of Ms Leave sample studied, FMs from Arbaminch contained highest concentration (237 0.001 mg/100g) of AA, Followed by FMs from Konso (233 0.48 mg/100g and FMs from Dilla (21 0.48 mg/100g), respectively. But it was reduced significantly after boiling for ten minute. The level of AA content in the analyzed Ms Leave samples was found to decrease with increasing cooking time. Cooked Ms Leave sample contained lower concentration of AA than Fresh M. stenopetala leave sample. All studied Ms Leave samples contained relatively acceptable range or moderate amounts of total AA (200-250 mg/100g) and the results obtained from the modified UV-vis Spectrophotometric and HPLC methods were statistically consistent.