Effects of interfering substances on the determination of L-ascorbic acid (AsA) in green tea and it´s extracts by 2, 4-dinitrophenylhydrazine (DNP) method was studied, and the removal of these interfering substances was also investigated. Under the condition prescribed for DNP method, AsA content of green tea are effected by some sugar, reductones, dicarbonyl compounds, organic acids, amino acids and others. All interfering substances except amino acids were eliminated by the chloroform extraction after adding o-phenylendiamine to sample solution, and remaining amino acids were eliminated almost completely by the treatment with ion exchange resin(Amberlite IR-120 H^+).
After removing the interfering substances by the above mentioned procedure, total AsA in green tea was determined by DNP method. The values obtained by this method were in good agreement with those by thin layer chromatography (TLC) method, and the method was more rapid and simple than TLC method.
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