Vitamin C lab report free essay sample

Vitamin C, also called ascorbic acid, is a water soluble vitamin. It is a powerful reducing agent that is able to decolourise blue DCPIP (2. 6-dichlorophenol indophenols). The decolourisation of DCPIP can therefore be used to calculate the vitamin C content of a variety of fruit juices. Research Question – To determine how the content of Vitamin C (%) will differ in fresh fruits (orange, mango, lemon, lime, blackcurrant, pineapple) from that in processed fruit juices (orange, pineapple) by adding drops of the aforementioned fruit juices to DCPIP until the DCPIP gets decolorized. Variables Independent Variable – Type of fruit juice used (fresh or processed). NB: the juice from the fruits was freshly squeezed during the experiment. Dependent Variable – Amount of fruit juice it takes to decolourize the DCPIP in cm3 (Â ±0. 2cm3) Controlled Variables – 1) Concentration of DCPIP was the same in all the samples. A larger amount of it was prepared for this case. 2) The same amount of DCPIP was added in each test-tube (1 cm3) using the same 5cm3 syringe 3) All the fruit juices, fresh and processed, were diluted five times. We will write a custom essay sample on Vitamin C lab report or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page The same 5cm3 syringe was used to add drops of fruit juices in the test tubes 5) State of decolourization – one sample of decolourised DCPIP was used as a basic one (one with 0. 1% ascorbic acid) and later all the fruit juices with DCPIP were compared with the sample. The decolourization should have been the same in both the samples. 6) The other control was similar to (5) above, but instead of having ascorbic acid, it had distilled water. It was used to show that only vitamin C can decolourize DCPIP Materials 10 Test Tubes 2 x 5cm3 syringes (Â ±0. 2cm3) (pipettes were not available so syringes were used) 3 x 20 cm3 beakers Label the test tubes, then slowly pipette 1 cm3 of DCPIP into each test tube Safety! – DCPIP is corrosive and toxic. Wash of any spills with water 2) Take 5cm3 of 0. 1 % ascorbic acid using a syringe 3) Add the ascorbic acid drop by drop into the first test tube, gently shake the tube after each drop is added. As soon as the DCPIP becomes decolourized, note the volume of ascorbic acid that was added 4) Wash syringe and beaker. Into the second test tube, add the same volume of distilled water as ascorbic acid that you added in test-tube 1. Gently shake the tube and note observations. 6) Dilute all juices to be tested 5 times using a measuring cylinder. 7) Add the first sample of juice drop, gently shake the tube after each drop is added and note the volume added in order to decolourize the DCPIP. Continue the same way for other fruit juices Do not forget to wash out the beaker and the pipette after each juice is used 8) Lastly, calculate the concentration of ascorbic acid present in each fruit juice: Data Collection – Qualitative – Table 1: Colour change in each liquid test Tube Liquid test Colour 1 0. 1% ascorbic acid (control) colourless 2 Distilled water (control) No change 3 0range juice(fresh) colourless 4 Lemon colourless 5 Mango colourless 6 Lime colourless 7 blackcurrant magenta 8 pineapple colourless 9 Processed orange juice Turns light purple/maroon 10 Processed pineapple juice Pink From the table on the previous page it can be seen already that most fresh fruit juices have high amounts of vitamin C as they completely decolourise the DCPIP (comparing to test tube 1 which is the control). Moreover, both of the processed juices seem to have lower amounts of DCPIP as they hardly change from their original colour (purple). None of the final colours were similar to that with distilled water, showing that all of them had some amount of ascorbic acid. Quantitative Data In the following table, the test-tube with distilled water will not be taken into account as the DCPIP was not decolourized. Table 2: amount of volume required to decolourise DCPIP in each liquid test Tube Liquid Test Volume (cm3/(Â ±0. 2cm3) added to decolorize DCPIP 1 0. 1% ascorbic acid (control) 0. 6 3 0range juice(fresh) 2 4 Lemon 3. 1 5 Mango 3 6 Lime 2. 9 7 blackcurrant 18 8 pineapple 6 9 Processed orange juice 20 10 Processed pineapple juice 18 The data in this table supports the qualitative results. It should be noted that due to time constraints, for test-tube 7, 9 and 10 the experiment was stopped as they didn’t change colour quickly and continuing the experiment would have been time consuming. The fact that they decolourised from their original colour was taken as proof that ascorbic acid was present. Data Processing Using this formula the concentration of ascorbic acid in all the liquids was found Volume of 0. 1 % ascorbic acid is 0. 6 cm3 (Â ±0. 2cm3). Table 3: Concentration of ascorbic acid (%) in liquid tests Tube Liquid Test Volume (cm3/(Â ±0. 2cm3) added to decolorize DCPIP Concentration of ascorbic acid (%) 1 0. 1% ascorbic acid (control) 0. 6 3 0range juice(fresh) 2 0. 03 4 Lemon (fresh) 3. 1 5 Mango (fresh) 3 6 Lime (fresh) 2. 9 7 Blackcurrant (fresh) 18 8 Pineapple (fresh) 6 9 Processed orange juice 20 10 Processed pineapple juice 18 Presenting Processed Data The following bar graph shows the amount of vitamin C present in each of the liquid tests. It shows that test tubes 7, 9 and 10 have the least amounts of Vitamin C while from the fruit juices, test tube 3 has the highest amount of vitamin c. Note: test tube 1 is a control with ascorbic acid (0. 1%). Graph 1: Concentration of Ascorbic acid (%) against fruit juices From Table 3, it can be seen that greater the volume of liquid required to decolourise the DCPIP, smaller the concentration of ascorbic acid (%) in the solutions. The following graph shows this relationship even more clearly. The plots were joined using a trend line so that the trend can be seen more clearly. Graph 2: Concentration of ascorbic acid (%) against Volume (cm3/(Â ±0. 2cm3) added to decolorize DCPIP The following graph shows that the concentration of ascorbic acid (%) in the fresh fruits (indicated by the blue diamond-shaped dots) is higher than the concentration in processed fruit juices (indicated by the blue squares). All the points in the fresh fruits line are higher than those in the processed fruit line. Since we could not get the processed juices for all the fresh fruits, the following graph will focus on the vitamin C concentrations of orange and pineapple, both fresh and processed. Graph 3:Fresh orange and Processed orange Graph 4: Fresh pineapple and Processed Pineapple Juice This clearly shows that there is a higher vitamin C concentration in the fresh fruits (3 and 8) than in the processed fruit juice (9 and 10) Conclusion Putting the above results from highest Vitamin C concentration to lowest; Ascorbic Acid (1st) Fresh Orange Juice Fresh lemon Fresh Mango Fresh Lime Fresh pineapple Fresh Blackcurrant Processed Orange juice Processed Pineapple juice Distilled water (last) From this ranking, it can be said that from the fruit juices/ Fresh orange juice (0.03%) has the highest amount of Vitamin C and the processed fruit juices (orange, pineapple) have the lowest amount (0. 003%) Even though only 2 comparisons could be made (Graph 4 and 5), the results of this investigation illustrate without any doubt that fresh fruit juices(orange, mango, lemon, lime, blackcurrant, pineapple) have a higher concentration of ascorbic acid (%) than do processed fruit juices (pineapple, orange). The research question can thus be answered as: the concentration of Vitamin C is higher in fresh fruits than processed juices. Therefore, if our diet consists more of the fresh fruits above, we will gain a higher amount of vitamin C in our bodies. Evaluation 1) Oranges are ranked as world’s healthiest fruits because of their high Vitamin C concentration. One orange has 69. 62mg of Vitamin C and can supply 116. 2% of the daily value1. This fact is consistent with the findings of the experiment, where the concentration of ascorbic acid in fresh orange is the highest from all the samples tested (0. 03%) 2) All the fruits used were fresh and bought on the same day. This increased reliability of the results since the age of the fruit may affect Vitamin C content. 3) Water was used as a control in the experiment to ensure the fact that only items with vitamin C can decolourize DCPIP. 4) A syringe was used to drop the fruit juices in to the test tubes since a pipette was not available. The problem with a syringe is that if too much pressure is applied, the entire solution can be poured out and it has an uncertainty of (Â ±0. 2cm3). Maybe it would have been better to use a burette, which also has a lower uncertainty (3) 5) We were told that the concentration of ascorbic acid provided was 0.1%. We were not however sure because we did not see it being made. In this case, we should have made the solution to that concentration ourselves, or the lab technician should have made it in front of us. 6) A limitation of this investigation was that the maturity stage of the fruits was not determined. Vitamin C concentration decreases during the ripening process. Unripe fruits have more ascorbic acid than the ripe ones. Since the ripening stage was not informed, the ascorbic acid concentration could have varied and therefore affected the results of the experiment. Even the position of the fruits on the tree was not known; sunlight exposure enhances vitamin C levels. Maybe some fruits were on the shadier side showing low levels of vitamin C. 7) The observations in this experiment were made solely by the eye. There was thus huge room for human error, as sometimes, two drops could seem one drop. In this case, two people could have been used to watch the drops and increase reliability of results 8) Blackcurrant is a fresh fruit which has a very high concentration of vitamin C. However the results of this investigation showed otherwise. This may indicate a shortcoming in the experiment because this fruit was the only one which did not show a high concentration of vitamin C. Maybe the juice became a bit too dilute. This could have been rectified if time had allowed. Due to time constraints, this experiment was only carried out once. In order to obtain reliable results however, the experiment should have been carried out three times, and the average volume of liquids required to decolourize could have been obtained, giving a more realistic picture of the concentrations. Another limitation was that besides orange and pineapple, the processed juices of other fresh fruits were not available and so they could not be directly compared to each other. However, the results did show that processed fruit juices had low Vitamin C content. 10) If time would have permitted, the experiment for 7, 9 and 10 should have been continued so as to obtain the exact end point when the DCPIP got decolorized and therefore get the exact concentration of ascorbic acid (%) in those liquid tests.