Indirect Photometric Determination of Ascorbic Acid in Drugs

In an acetate buffer of pH 4.6,and in the presence of CTMAB,Fe(Ⅲ) ion was quantitatively reduced by ascorbic acid to Fe(Ⅱ) ion.A colored coordination complex was formed between the Fe(Ⅱ) ion and 5-nitro-1,10-phenanthroline reagent,with its absorption maximum at 502 nm,and value of molar absorptivity (ε502) 2.48×104L·mol-1·cm-1.Beer′s law was obeyed in the range of 0.1-2.0 mg·L-1 of ascorbic acid.Samples of vitamin C tablets,chewing tablets and injection were analyzed for their ascorbic acid content by the proposed method,giving results in consistency with those obtained by the iodi metry