Abstract
Two simple and sensitive spectrophotometric methods (A and B) have been described for the determination of ascorbic acid. Method A is based on the oxidation of ascorbic acid (AA) by known excess of Se(IV) in hydrochloric acid medium and subsequent determination of unreacted Se(IV) by reacting it with iodide in the same acid medium to liberate iodine, which react with starch to form a stable blue coloured iodine-starch complex, which shows maximum absorbance at 590 nm. Method B is based on the oxidation of ascorbic acid (AA) by known excess of Cr(VI) in sulphuric acid medium and the determination of unreacted Cr(VI) with diphenyl carbazide (DPC) under the same acidic medium to produce a stable red-violet coloured species, which shows a maximum absorbance at 550 nm. The reacted oxidants (in methods A and B) correspond to the AA content. The apparent molar absorptivity values are found to be 1.627×104and 1.641×104L mol-1cm-1for methods A and B, respectively. The proposed methods are simple, sensitive and suitable for the routine analysis of AA in pharmaceutical formulations and in real samples.
Highlights
Ascorbic acid occurs in different concentrations in a variety of natural samples
Few indirect spectrophotometric methods have been reported for analysis of ascorbic acid (AA) utilizing iron(III) – thiocyanate complex[8] and ferrozine[9] Even these procedures are unsuitable for routine analysis, since the iron(III) – thiocyanate[8] method required expensive experimental set-up [FIA]
To overcome these limitations in the existing methods, there is still a need for a sensitive and cost-effective method for the determination of ascorbic acid that can be employed for the routine analysis of it in pharmaceuticals as well as in real samples
Summary
Ascorbic acid occurs in different concentrations in a variety of natural samples. It is added to several pharmaceutical products as an essential ingredient, a stabilizer for vitamin B complex, and as an anti-oxidant. Consequent upon its desirable effects, it is widely used in the treatment of certain diseases such as scurvy, anaemia, haemorrhagic disorders etc It is considered essential for the development and regeneration of muscles, bones, teeth and skin. Few indirect spectrophotometric methods have been reported for analysis of AA utilizing iron(III) – thiocyanate complex[8] and ferrozine[9] Even these procedures are unsuitable for routine analysis, since the iron(III) – thiocyanate[8] method required expensive experimental set-up [FIA] To overcome these limitations in the existing methods, there is still a need for a sensitive and cost-effective method for the determination of ascorbic acid that can be employed for the routine analysis of it in pharmaceuticals as well as in real samples. Aqueous solution of ascorbic acid (AA) [Merck] was prepared daily by dissolving the required amount of the sample in doubly distilled water.
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