Lab Report 8

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Florida International University *

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Chemistry

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Jan 9, 2024

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Laboratory Report for Antioxidants Lab (Sections E & F) Student Name: Sachintha Peiris Date: 11/1 TA Name: Lukkamol Prapkree E. Data Record and Lab Write-up (20 points) Vitamin C 1. Record beginning volume and ending volume of buret. Determine iodine required to titrate standard solution and 10 ml juice samples. Table 1: Iodine solution volume (ml) Vitamin C Standard (10 mg/10 ml) Fresh juice Boiled juice Trial 1: Begin: 0 ml End: 4.5 ml Vol: 4.5 ml Begin: 4.5 ml End: 6.4 ml Vol: 1.9 ml Begin: 6.4 ml End: 7.6 ml Vol: 1.2 ml Trial 2: Begin: 7.6 ml End: 12.4 ml Vol: 4.8 ml Begin: 17.2 ml End: 19.1 ml Vol: 1.9 ml Begin: 21 ml End: 22.3 ml Vol: 1.3 ml Trial 3: Begin: 12.4 ml End: 17.2 ml Vol: 4.8 ml Begin: 19.1 ml End: 21 ml Vol: 1.9 ml Begin: 22.3 ml End: 23.6 ml Vol: 1.3 ml Average: Vol: 9.7 ml Vol: 1.9 ml Vol: 1.3 ml Substract the end volume from the beginning volume for each trial. You will then add up all 3 and find the average for each solution as shown in the video. 2. Calculate oxidizing equivalents of iodine solution used in titration, i.e. conversion factor: 2.13 [Use formula below] 10 mg vitamin C in standard 4.7 ml iodine (average) used in titration = conversion factor To find the conversion factor, you will plug in the average volume from the Vitamin C Standard to this equation. 1

Show your work: 10/ 4.5+4.8+4.8 = 10/9.7 3. Calculate milligrams of vitamin C in 10 ml juice samples using the following formula: 50 ml iodine used in titration X Conversion Factor (calculated above) = 106.5 mg vitamin C in juice You will now multiply the average volumes for fresh and boiled juice by the conversion factor found in #2. Table 2: Juice Type 10 ml Fresh juice 10 ml Boiled juice Vitamin C (mg) ORANGE 1.9 x 10/4.7 (2.12) 2.8 mg 4. Calculate the mg Vitamin C per 4 oz . serving of fresh juice: _____________ **Hint: You have now calculated the number of mg Vitamin C in a 10ml sample of your juice. How many mg would be in a 4 oz. serving if 1oz. is equal to 30ml? Show your work: 4x30=120ml Carotenoid Determination Vegetable Sample: Carrot Mass of initial vegetable sample: 5 grams Volume of pigment solution following extraction: 6.5 ml Table 1: Record the absorbances for each of your carotenoid replicates below. Cuvette # Food sample ABS 1 ABS 2 ABS (avg) 1 carrot 1.96 2.02 1.99 2 carrot 2.04 2.03 2.035 Average Absorbance for pigment solution: 10.465 (Enter the Average Absorbance for your pigment solution above into the calculations below to determine the Total Carotenoid in your food sample) Calculations: 2

Total carotenoid in sample = (Absorbance) (volume) (10 4 ) = 10.465 Total carotenoid in sample = (2500) (grams of vegetable) Where Absorbance is your average absorbance reading above; volume is the volume you brought the pigment solution up to in your graduated cylinder; and ‘grams of vegetable’ is the initial mass of your food sample; 2500 is a generalized extinction coefficient for natural pigments. Show your work: Total Carotenoid in your vegetable sample: 10.5’ F. Discussion Questions (30 points) 1. Explain how antioxidants like Vitamin C work in the body? In what parts of the body would an antioxidant like Vitamin C be most useful? Where would fat- soluble antioxidants like beta-carotene be most useful? Be specific. (5 points) Antioxidants like Vitamins C work in the body giving electrons to free radicals, preventing damage to cells. These antioxidants are most useful for repairing blood cells and skin cells. Fat soluble antioxidants are more useful in the liver organ. 2. How did boiling affect the vitamin C content of the orange juice? Is this what you expected? Why or why not? (5 points) The boiling reduced the vitamin C content. This was expected because boiling reduces nutrition. 3. In your own words, explain the chemical principles behind the technique of titration. (5 points) Titration is the use of a solution to determine the concentration of an unknown solution. This is done by measuring the reaction of the solution. 4. What is meant by the term ‘total carotenoid’ in sample? List the major constituents that are likely to be contained in the total carotenoids in your vegetable sample? (5 points) The term means that they are fat soluble antioxidants. Major constituents that are likely to be contained in the vegetable sample include triacylglycerols and phospholipids. 5. Was there any variation between the 3 titrations (replicates) for your juice sample? Please list and explain the most likely sources of variation in this experiment. (5 points) Yes there was and this was most likely due to the iodine level in each sample. 3

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6. Based on your 24-hour recall results, what kinds of food did you consume that contained Vitamin C? What about carotenoids? Why is it important for you to consume fruits and vegetables that are high in antioxidants? (5 points) I consumed various fruit juices that contained vitamin C, I also consumed berries, carrots and green beans. This is important because it helps reduce diseases. 4