Comparison of Vitamin C Content - Lab Report Example

Aim To compare the vitamin C content between the new range of drinks and the previous range of drinks. Introduction Vitamin C or ascorbic acid is an essential vitamin which is required by our body for various purposes. This helps in building connective tissue (by helping to form collagen), healing wounds, and maintaining healthy blood vessels. The antioxidant properties of this soluble vitamin C prevent infections and other diseases; and thus help in maintaining a healthy immune system. Deficiency of this vitamin leads to disease called scurvey. Other clinical symptoms like include colds, depression, high blood pressure, arthritis, allergies and cholesterol gallstones can also appear when the requirement of vitamin C is not met in our diet. The daily amount of vitamin C which is must in our diet is referred as Recommended Dietary Amounts, RDA. The daily dosage is 75-90 mg of ascorbic acid for the average person. These RDA vary depending on health, age, weight, activity, energy level and metabolism. This can not be prepared by human being, so we have to include it in our healthy diet. It is found in high concentrations in citrus fruits like orange, lemon, kiwi, blackcurrant, peach etc and green plants such as green peppers and spinach (Boyer, 1993). Ascorbic acid or vitamin C can be determined by oxidation –reduction titration. The dye 2,6-dichlorophenolindophenol (DCP) is used as an oxidising agent to analyse ascorbic acid content in fruit juices. DCP is blue in color. The blue dye DCP is reduced by ascorbic acid. Ascorbic acid is oxidized to dehydroascorbic acid as shown in Figure 1 (Gillete year). The reduced form of DCP is colourless. However, this blue DCP titrant turns pink/red at acidic pH. DCP solution being unstable is stored in dark bottle at 4ºC. DCP titrant has to be standardised using known concentration of vitamin C. This helps in accurate determination of the concentration of vitamin C in an unknown solution. Predicitions Blackcurrants are reported as richest source of vitamin C, followed by oranges. The strength of vitamin C in lemons is considered less as compared to oranges The amount of vitamin C varies between different varieties of the same species depending upon cultivation conditions, storage, stage of ripening etc (Natural Food Hub). Therefore, it is difficult to predict which soft drink contains more amount of vitamin C, unless they are properly analysed. Materials Apparatus: pipettes (1 ml, 5ml), conical flasks, test tubes, beakers etc. Reagents and samples: Blue dye 2,6-dichlorophenolindophenol (DCP) solution, a solution containing a known amount of vitamin C, old products- a lemon, orange and blackcurrant drink, new products - a lemon, orange, and blackcurrant drink. Method To compare the strength of vitamin C in the soft drinks with known concentration of vitamin C, first standard solution of vitamin C should be reacted with a blue dye solution. Then, the amount of vitamin C in a variety of soft drinks can be worked out by finding out how much must be added to 1 ml of the blue dye to turn it clear. Procedure Accurately pipette out 1 ml of blue dye DCP solution into a test tube. Then slowly add the chosen soft drink solution dropwise with the pipette. Stir the mixture properly. The further additions of test samples should be done until the blue solution turns completely colorless. This end point is noted carefully. All the steps should be repeated for other fruit soft drinks also. The analysis of each soft drink should be performed in triplicate and then an average should be considered for calculation purpose. The amount of ascorbic acid equivalent to 1 ml dye can be calculated with the help of known standard solution of vitamin C. This in turn, would help for the determination of vitamin C content in various old and new soft fruit drinks. Precautions It has been reported that the storage and handling of ascorbic acid containing samples significantly affects vitamin C content in them. Since vitamin C in a solution is highly unstable and sensitive to atmospheric oxygen, heat and light; it decomposes easily. This might cause reduction in the content of vitamin C in the fruit juice. From analytical point of view, dye solution and standard ascorbic acid solution should be made accurately and carefully stored to avoid further inaccuracies in the results. The sample fruit juice solution should be added dropwise to the accurately pipetted 1 ml blue dye solution and should be well mixed for proper distribution of two solutions. Once all the DCP or blue dye solution is reduced by vitamin C, the blue solution turns colorless. This end point should be noted carefully to avoid variation in results. The altered addition of fruit juice might influence the amount of ascorbic acid content in the samples (Biology investigations, 2008). All these precautions are necessary to ensure a fair analysis. Variables Independent variables in this analysis are use of same freshly and accurately prepared standard ascorbic acid solution and DCP solution. The dependent variable is the different volume of soft drink needed to decolourise DCP solution. This dependent variable is directly proportional to the amount of ascorbic acid present in the sample. Results The volume of fruit soft drink solution added to 1 ml dye solution of all the samples should be tabulated. The differences in the ascorbic acid content should be observed between the new range of drinks and the previous range of drinks. The amount of ascorbic acid (mg) in old products- a lemon, orange and blackcurrant drink, new products - a lemon, orange, and blackcurrant drink could be presented and compared by plotting bar charts. Calculations The amount of ascorbic acid equivalent to 1 ml dye can be calculated with the help of known standard solution of vitamin C. This can be used for future calculations. The concentration of vitamin C in unknown samples can be expressed as “mg of ascorbic acid oxidized per ml of 2,6-dichloroindophenol solution”. Conclusion The results obtained would demonstrate vitamin C content of a new range of drinks more/ less than the previous range of drinks. References Biology investigations: Teaching notes (2008) URL: https://www.ibid.com.au/ibid/web.nsf/reslookup/312/$file/Biology%20Options%20TN%20for%20www.pdf Boyer, Rodney F. (1993) Modern Experimental Biochemistry, 2 nd ed, Benjamin Cummings. Gillete M. L. et al. Modular laboratory program in chemistry: Analysing vitamin C in fruit juices. In: Gillete M. L. et al. (eds) ANAL 622. Neidig H. A. p. 1-6. Natural food-Fruit Vitamin C Content, The Natural Food Hub, URL: http://www.naturalhub.com/natural_food_guide_fruit_vitamin_c.htm Variables The independent variable in this experiment will be the soft drinks used as there will be a mixture of old and new flavours. This in effect will affect the dependant variable which is to measure how much soft drink is needed to decolourize DCPIP. Read More