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. We all recognize citrus fruits as a valuable vitamin C source, but few of us realize that many freshly harvested vegetables contain considerably more of this vitamin than do oranges or lime. Unfortunately, storage and processing destroy most of the Vitamin C in vegetables before they reach the consumer. Consumer cooking methods further decrease the amount of vitamin C in vegetables.
Vitamin C is water soluble and thus leaches out while cooking or steaming. 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. Please note the equation for the reaction below: C6H8O6 (colorless) + C12H7O2NCl2(red) >(pH3) C6H6O6 (Colorless) + C12H9O2NCl2 (colorless) This titration is particularly convenient mainly because DCP as well serves as its indicator. Even as add DCP solution to an answer containing Nutritional C, the reaction mixture is still colorless till all of the Vitamin C has been converted to dehydroascorbic acid.
The next drop of DCP answer added imparts a red colorization from excessive DCP for the mixture, implying both the assent point plus the endpoint in the titration. (Expect solution to move from reddish colored to without color then in the endpoint crimson again). Mainly because DCP alternatives have a comparatively short life, we usually standardize such solutions instantly prior to using them. We can conduct the standardization conveniently by simply titrating aliquots of an ascorbic acid solution prepared from an accurately-weighed sample of reagent-grade ascorbic acid. The standardization titration reaction is equivalent to the research reaction over.
In this research, you will begin by simply standardizing a DCP remedy. Then you can determine the vitamin C content of liquid and solid meals samples by titration with the standardized DCP solution. Just before performing the titrations, you are going to treat the food samples with metaphosphoric acid solution. Treatment with this chemical p serves to denature and precipitate protein that would or else interfere with the analysis.
Acidification of thesample also provides to support the ascorbic acid, that may otherwise break down and be undetected. Acidification to pH less than 4 also minimizes result of DCP to compounds which will react with DCP only at pH levels greater than 4.