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quantitive estimation of ascorbic acid

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Introduction

Quantitative Estimation of Ascorbic Acid Aim: To find out the concentration of ascorbic acid with samples of different fruit juices by using DCPIP to help record the volume of ascorbic acid when it is decolourised. Introduction: What is ascorbic acid? Ascorbic acid is an antioxidant which is used to prevent the oxidation of fats and oils by atmospheric oxygen, resulting in the development of rancid flavours. It is also added to foods as antioxidant to protect the colour and aroma of the food. It is also known as vitamin C and is soluble in water. A majority of animals can synthesize their own ascorbic acid within the liver, with the exception of primates (humans). What is it used in the body for: Ascorbic acid is vital for the production of collagen because collagen gives bones, teeth, cartilage, blood vessels and muscles their structure. Ascorbic acid is also used for the synthesis of bile acid, maintaining skin elastic, aiding in absorption and improving resistance to infection. ...read more.

Middle

Use a syringe to transfer 1.0cm3 of DCPIP solution into a test tube. 2. Fill another 1cm3 syringe with 0.1% ascorbic acid solution and, keeping the end of the needle below the surface of the DCPIP, and then carefully add the ascorbic acid solution until the DCPIP is decolourised. Do not shake the mixture; it may gently stirred using the needle. 3. Record the volume of ascorbic acid solution required to decolourise the DCPIP. 4. Afterwards repeat this test with 1.0cm3 of DCPIP solution and a sample of fruit juice e.g. lemon. 5. Record the volume of fruit juice required to decolourise the DCPIP. 6. Finally repeat this procedure with samples of different fruit juices. Results: Original Results: Sample used with 0.1% DCPIP solution: Volume required to decolourise 0.1% of DCPIP solution cm3(1st time): Volume required to decolourise 0.1% of DCPIP solution cm3 (2nd time) Colour Change: Ascorbic Acid 0.38 0.75 Yellow Grapefruit Juice 0.73 0.66 Purple Orange Juice 0.88 0.66 Purple Pineapple Juice 0.89 0.94 Purple Lime Juice 0.87 0.90 Purple This is my original results table showing the volume required to decolourise the DCPIP solution measured in cm3. ...read more.

Conclusion

My first graph is a bar chart showing the volume required to decolourise the DCPIP solution against the samples of fruit juices. My other graph is showing the concentration of ascorbic acid against the sample of fruit juices. Conclusion: My conclusion is that the smaller the volume required for the fruit juices to decolourise the DCPIP solution the higher the concentration of ascorbic acid that is present. My graph gives evidence for this for my results showed that grapefruit had the smallest volume required to decolourise the 0.1% DCPIP solution. Also my results showed that the fruit sample with the highest volume to decolourise the DCPIP solution had the lowest concentration of ascorbic acid present (which was the pineapple in my experiment). I think this is because of the pineapple having a smaller concentration of ascorbic acid means that a higher volume of it is used to decolourise the DCPIP solution. This also is due to the lack of vitamin C that it has. Violet J. Lule Biology C/W 5 ...read more.

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