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Quantitative Analysis of Vitamin C in Food Products.

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Quantitative Analysis of Vitamin C in Food Products Theory Review There is growing evidence that Vitamin C serves as a potent antioxidant in vitro. There are many functions that Vitamin C has in the body among which is the capacity to improve the immunity system such that a person is more able to fight off colds and flus. Pre-Lab: List five other functions of Vitamin C in the human body. Vitamin C is another name for ascorbic acid. There is a marked similarity between the structure of glucose and Vitamin C. As a matter of fact, plants and most animals are able to synthesize Vitamin C from glucose. Unfortunately, humans are unable to do this and we must include Vitamin C in our diet or we risk a vitamin deficiency disease. ...read more.


One useful analytical method for measuring the Vitamin C content of a vegetable or fruit involves an oxidation-reduction titration of ascorbic acid. In the titration, ascorbic acid is oxidized to form dehydroascorbic acid. You might think it unusual to oxidize the acid rather than titrate it with a base. However, biological samples contain many substances that also act as acids (as was mentioned in Experiment 3) and thus interfere in a titration of ascorbic acid with a base. In contrast, many fewer components of biological materials interfere with the oxidation of ascorbic acid by the oxidizing agent 2, 6-dichloroindophenol (DCP). Thus, an oxidation-reduction titration of ascorbic acid with DCP provides a more selective analysis than would an acid-base titration. ...read more.


We can perform the standardization conveniently by titrating aliquots of an ascorbic acid solution prepared from an accurately-weighed sample of reagent-grade ascorbic acid. The standardization titration reaction is the same as the analysis reaction above. In this experiment, you will begin by standardizing a DCP solution. Then you will determine the vitamin C content of liquid and solid food samples by titration with the standardized DCP solution. Prior to performing the titrations, you will treat the food samples with metaphosphoric acid. Treatment with this acid serves to denature and precipitate proteins that would otherwise interfere with the analysis. Acidification of thesample also serves to stabilize the ascorbic acid, which will otherwise decompose and be undetectable. Acidification to pH less than 4 also minimizes reaction of DCP with other compounds which react with DCP only at pH levels greater than 4. ...read more.

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