1983 Volume 30 Issue 7 Pages 414-420
A spectrophotometric method based on the difference spectra before and after oxidation of L-ascorbic acid(AsA)by ascorbate oxidase(EC 1. 10. 3. 3)was developed as a simple, rapid and sensitive method for AsA estimation. The present paper describes the determination of dehydroascorbic acid(DAsA)and total AsA(AsA+DAsA)by this difference spectral(DS) method. First the reduction condition of DAsA with dithiothreitol(DTT)was investigated. DAsA was completely reduced to AsA by the treatment with 100mg% DTT-ethanol solution for 15 min at 30°C. After the reduction, total AsA was determined by the DS method, DAsA being calculated from the difference between total AsA and AsA. The values of total AsA and AsA estimated by the DS method and the 2, 4-dinitrophenylhydrazine(DNP)method agreed very well in satsuma mandarin and tomato juice samples used. But, the DAsA values obtained by the DS method were lower than those by the DNP method, in which 2, 3-diketogulonic acid value was uncorrected, in satsuma mandarin juice. The recovery of DAsA added to the juice sample ranged from 101 to 103%. Thus, it is possible to determine not only AsA but also total AsA and DAsA by the DS method.
