Background Correction Method for Determination of Ascorbic Acid in Baobab Fruit Pulp Using Direct UV Spectrophotometry
Ibrahim Yaagoub Erwa
Department of Applied and Industrial Chemistry, Faculty of Pure and Applied Sciences, International University of Africa, Khartoum, Sudan
Mahgoub Ibrahim Shinger *
Department of Applied and Industrial Chemistry, Faculty of Pure and Applied Sciences, International University of Africa, Khartoum, Sudan
Omer Adam Omer Ishag
Department of Applied and Industrial Chemistry, Faculty of Pure and Applied Sciences, International University of Africa, Khartoum, Sudan
*Author to whom correspondence should be addressed.
Abstract
Herein a background correction method has been utilized for the estimation of ascorbic acid in baobab (Adansonia digitata L.) fruit pulp using direct UV spectrophotometry. The background correction based on catalytic oxidation of the acid by copper (II). EDTA was used to correct the absorption due to copper (II). The absorbance and remained essentially constant at 267 nm at pH range from 6 to 8, with highest absorption at pH 6. The calibration graph was linear up to 20 μg ml-1 of ascorbic acid, correlation coefficient (r = 0.9998) and the molar absorptivity was 1.52 × 104 l mol-1 cm-1. The mean value of ascorbic acid was 237 ± 18 mg/100 g using the proposed method and 250 ± 15 mg/100 g using indophenol official method. The statistical analysis of data revealed no significant difference in precision of the two methods and there is no evidence that the two sets of results are significantly different at 95% confidence interval. The proposed method is selective, accurate and acceptable for determination of ascorbic acid in baobab fruit pulp.
Keywords: Adansonia digitata L., baobab fruit pulp, ascorbic acid, background correction