Quantitative Analysis of Vitamin C in Food Products Essay
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 very convenient since DCP as well serves as its own indicator.
Even as we add DCP solution to an answer containing Supplement C, the reaction mixture remains colorless until all of the Supplement C continues to be converted to dehydroascorbic acid. The next drop of DCP solution added imparts a red colorization from excessive DCP towards the mixture, suggesting both the assent point as well as the endpoint of the titration. (Expect solution to get from reddish colored to without color then on the endpoint crimson again). Since DCP alternatives have a comparatively short life, we generally standardize this kind of solutions immediately prior to using them.
We can carry out the standardization conveniently by simply titrating aliquots of an ascorbic acid remedy prepared from an accurately-weighed sample of reagent-grade ascorbic acid. The standardization titration reaction is equivalent to the evaluation reaction previously mentioned. In this experiment, you will begin simply by standardizing a DCP remedy. Then you will certainly determine the vitamin C content of liquid and solid foodstuff samples by titration with the standardized DCP solution. Ahead of performing the titrations, you will treat the food samples with metaphosphoric chemical p. Treatment with this chemical p serves to denature and precipitate protein that would normally interfere with the analysis.
Acidification of thesample also will serve to strengthen the ascorbic acid, which will otherwise decompose and be undetected. Acidification to pH less than 4 as well minimizes reaction of DCP with other compounds which in turn react with DCP just at pH levels more than 4.
