Abstract

K. F. Akhter, M. A. Mumin, M. Z. Abedin* and M. N. Siddiquee

This study presents a spectrophotometric method for the comparative determination of total vitamin C (ascorbic acid and dehydroascorbic acid) content in various fruits and vegetables that are available in greater Sylhet. In this method samples were prepared by 10mM KH2PO4 solution (pH =1.4). Sample treatment entails SPE with Sep-Pak C18 (500 mg) cartridges. The spectrophotometric method involved the oxidation of ascorbic acid to dehydroascorbic acid by bromine water in presence of phosphoric acid. After coupling with 2,4-dinitrophenylhydrazine (DNPH) at a temperature of 37°C for three hours, the solution was treated with 85% H2SO4 to produce a red colored solution and the absorbance was measured spectrophotometrically at 520 nm. This study also includes percentage recovery, possible interfering factors and the statistical calculations. This study also modifies the incubation time from 3 hours at 37°C to 2 hours at 50°C for newly established extracting solvent of 10mM KH2PO4 (pH =1.4) solution and for conventional extracting solvent of 5%metaphosphoric acid – 10% acetic acid solution

Ascorbic acid; Dehydoascorbic acid; SPE; KH2PO4; DNPH

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