Abstract
A rapid progress in high performance liquid chromatography (HPLC) has been made recently and various procedures to apply it for differential determination of total vitamin C (AsA plus DAsA) in foods have been examined. In this report, we describe a method for total vitamin C determination by HPLC using 2,4-dinitrophenylhydrazine (DNPH) as the internal standard. (1) Addition of DNPH in a range of 100-1000μg/ml (AsA standard) hardly influenced the peak area of the remaining DNPH in the reaction system after the formation of osazone. (2) When shaking extraction was carried out for 5 min after the addition of ethyl acetate, the peak area of DAsA osazone in the chromatograms reached to the maximum, indicating that 5 min of shaking time is optimum for extraction. (3) The amounts of total vitamin C in 33 kinds of foods on the market were determind by using HPLC, TLC and DNPH method, and the results were compared among these three methods. The amounts estimated by the present HPLC method were close to those by TLC method and similar or lower than those by DNPH method. (4) The recovery of added total vitamin C was 95-106% for the present method. (5) Total vitamin C can be determined in concentrations 0.5 mg per 100 g of food.
