Apparatus: Burette, test tube, retort stand, 250ml beaker, measuring cylinder, funnel, test tube holder.
Materials: DCPIP, Ascorbic acid.
Method:
The method we followed is as follows:
We used 10ml of orange juice and used a burette filled with DCPIP to titrate the orange juice and so discover the amount of vitamin C it contained. We recorded the volume of the DCPIP used to turn the orange juice to a red-brown colour. When it turned this colour the volume was noted and the beaker with orange juice in it was cleaned out so as not to be contaminated by either the different juices or by the DCPIP. We knew that the more DCPIP needed to turn the juice to a red-brown colour the higher the concentration of vitamin C there was in the orange juice. We decided to use orange juice because it is the most widely available and there are many different types of orange juice such as UHT (where is it heated), fortified (where vitamins are added) and organic (where there are no artificial additives and where the fruit is grown organically, i.e.: there are no pesticides used).
Here is a Diagram of a typical titration experiment and how the apparatus is typically set up:
Prediction:
I predict that Sunny Delight will have the most Vitamin C as it is fortified with vitamins and is clearly a different colour from the other orange juices. None of the juices have bits in them and this is to keep the variable the same. The variable is the type of orange juice (the manufacturer or type such as UHT, fortified etc). What I will be keeping the same is the concentration of the solution of DCPIP and the amount of juice used each time.
The juices all have given amounts of vitamin C per 100ml on the packaging. They are as follows:
Waitrose- 25mg
Libby’s (original)- 24mg
Just Juice- 30mg
Libby’s (organic)- 25mg
Tesco- 25mg
Del Monte- 30mg
Sunpride- 26mg
Sunny Delight- 34mg
These help to predict what will happen and which will have the highest concentration of DCPIP. I think that Just Juice and Del Monte will have a large concentration of vitamin C followed by Sunpride, Tesco, Waitrose and the two brands of Libby’s. Its interesting to note that the original Libby’s has a lower concentration of vitamin C then the original Libby’s and I believe this is due to the fact that the original Libby’s underwent processing and this decomposes some of the vitamin C. It will be interesting to see if the juices live up to the manufactures claims and its good that I have used 10ml as 10 is a multiple of 100 and therefore very easy to use to work this out.
Preliminary Tests:
We tried 20ml of Just Juice to see if what we suspected that it was too much was true and we were right it took a large amount of DCPIP before it changed colour and so we tried it with 10ml of juice and it took a lot less DCPIP and still gave an accurate result that was easy to use for analysis.
OBTAINING EVIDENCE:
Results:
These three I have ringed are slightly anomalous.
My experiment was safe because we used safety goggles at all times and lab coats. Although not poisonous the DCPIP is very difficult to wash off if spilt.
I decided that I didn’t need to check any of the results as I had plenty to work with and I hoped I would still achieve a decent average.
ANALYSING AND CONSIDERING EVIDENCE
Its clear from the evidence that I have collected that Sunny Delight needs the highest concentration of DCPIP to change its colour and therefore has the highest concentration of vitamin C out of all the juices. It’s also clear that Waitrose has the least concentration of vitamin C.
I have drawn up two graphs. The first graph shows what is on the table but helps to make clear the concentration of vitamin C in the juices. The second graph is set out so as the variance can be measured to help check how accurate my results are. Both graphs use the average of the 3 experiments I did for each juice. The second uses the highest, lowest and the average volumes of DCPIP used for each juice in all the experiments.
The trend was that the higher the number of Mg’s of vitamin C per 100g’s of the juice the producer said their product contained, the higher the amount of DCPIP that was needed to change the juices colour. For example Waitrose claimed that their juice had 25 Mg’s of vitamin C per 100g’s and this was one of the lowest amount of vitamin C claimed and Waitrose juice contained the least vitamin C. One problem is that Libby’s original claimed that there was just 24 Mg’s of vitamin C in their juice yet it needed a lot more DCPIP to change its colour then Waitrose juice did which seems to suggests that there is a higher concentration of vitamin C in the Libby’s original brand. I think the solution to this is that when the Libby’s juice undergoes some processing some of the vitamin C will be lost and so the drink will have to be fortified, therefore I believe the manufacturers claim of 24 Mg’s of vitamin C in the juice is before the juice is fortified.
I decided to find out exactly the number of milligrams there were in each juice and to discover if what the manufacturer said was true.
The concentration of the DCPIP was 0.125%.
1g = 100ml 10ml = 0.1g 10ml = 0.1g = 100ml
100mg = 0.1g 10ml = 100mg
Waitrose:
25mg of vitamin C per 100 ml is the amount stated by the manufacturer.
25 over 100 as a fraction in its lowest terms is 1 over 40. As a decimal it’s 0.025.
There is 6.03ml of vitamin C per 10ml. This is the figure I came up with.
So 6.03x100 = 603
0.125x100 = 12.5
603 divided by 12.5 = 48.24 divided by 2 = 24.12
Libby’s (original):
24mg of vitamin C per 100 ml is the amount stated by the manufacturer.
24 over 100 as a fraction in its lowest terms is 6 over 25. As a decimal it’s 0.24.
There is 7.20ml of vitamin C per 10ml. This is the figure I came up with.
So 7.20x100 = 720
0.125x100 = 12.5
720 divided by 12.5 = 57.6 divided by 2 = 28.8
Just Juice:
30mg of vitamin C per 100 ml is the amount stated by the manufacturer.
30 over 100 as a fraction in its lowest terms is 3 over 10. As a decimal it’s 0.3.
There is 7.73ml of vitamin C per 10ml. This is the figure I came up with.
So 7.73x100 = 773
0.125x100 = 12.5
773 divided by 12.5 = 61.84 divided by 2 = 30.92
Libby’s (organic):
25Mg is the amount of vitamin C per 100 ml given by the manufacturer.
25 over 100 as a fraction in its lowest terms is 1 over 40. As a decimal it’s 0.025.
There is 6.38ml of vitamin C per 10ml. This is the figure I came up with.
So 6.38x100 = 638
0.125x100 = 12.5
638 divided by 12.5 = 51.04 divided by 2 = 25.52
Tesco:
25Mg is the amount of vitamin C per 100 ml given by the manufacturer.
25 over 100 as a fraction in its lowest terms is 1 over 40. As a decimal it’s 0.025.
There is 7.50ml of vitamin C per 10ml. This is the figure I came up with.
So 7.50x100 = 750
0.125x100 = 12.5
750 divided by 12.5 = 60 divided by 2 = 30
Del Monte:
30Mg of vitamin C per 100 ml is the amount given by the manufacturer.
30 over 100 as a fraction in its lowest terms is 3 over 10. As a decimal it’s 0.3.
There is 7.20ml of vitamin C per 10ml. This is the figure I came up with.
So 7.20x100 = 720
0.125x100 = 12.5
720 divided by 12.5 = 57.6 divided by 2 = 28.8
Sunpride:
26Mg of vitamin C per 100 ml is the amount given by the manufacturer.
26 over 100 as a fraction in its lowest terms is 13 over 50. As a decimal it’s 0.26.
There is 6.75ml of vitamin C per 10ml. This is the figure I came up with.
So 6.75x100 = 675
0.125x100 = 12.5
675 divided by 12.5 = 54 divided by 2 = 27
Sunny Delight:
34Mg per 100 ml is the amount of vitamin C given by the manufacturer.
34 over 100 as a fraction in its lowest terms is 17 over 50. As a decimal it’s 0.34.
There is 8.95ml of vitamin C per 10ml. This is the figure I came up with.
So 8.95x100 = 895
0.125x100 = 12.5
895 divided by 12.5 = 71.6 divided by 2 = 35.8
Therefore I discovered that many of the manufacturers were correct in their estimations of the amount of vitamin C in their juice. Its very interesting that Organic Libby’s has more vitamin C then the Original version. This could definitely be linked to the fact that the Original juice may go under processing which would destroy the vitamin C. Fortified drinks like Sunny Delight maybe make this a slightly unfair test as they have vitamins added to them so they don’t really test the vitamin C of the oranges although Sunny Delight is an orange juice therefore it comes under the right variable although clearly is a different colour and has different properties to the other brands.
My prediction on the whole was correct. It’s interesting to see the way UHT drinks like Just Juice perform in these experiments. UHT is where the substance is heated so as to completely sterilize it. Also known as pasteurization, the process takes place at 285 degrees Fahenheit (141 degrees centigrade) for a few seconds. The one thing about this is that high temperature destroys the vitamin C, which must mean they would have to add vitamin C after the pasteurization process.
All of the workings above seem to be close to what the manufacturers say is in their orange juice. Tesco seem to undersell themselves, although that may be down to a human error or an error in the experiment.
EVALUATING
My method I feel worked quite well although I think that more accurate results could be produced with changes to my method such as putting the juice in the burette. The only problem with this being that if the juice has bits in it then the burette would become blocked. Other problems were that the burette itself had the same colour numbers and lines on the scale as the colour of the DCPIP. This could have caused some problems and inaccuracy of readings.
I have circled some results that I feel to be anomalous on my table. Although not hugely anomalous they are slightly so. This could have been caused by the reasons I have stated above or they maybe other problems like the fact that all of the results were obtained by subjective observation, where we decided that there had been enough DCPIP added so one may have more or less then another therefore making it not a fair test and also giving us inaccurate results. Another reason for possible mistakes could be that we couldn’t see the scale below the DCPIP level thus making it difficult to read. We also could not stop the burette exactly when enough DCPIP had been added.
I drew two graphs to show variance so as to work out just how accurate my readings were. Variance is how you use your results and you see how accurate they are by how close the numbers are to each other. E.g.- 20 15 25 and 21 20 19. Both equal 20 but the second one is more reliable as the difference between the numbers is lower. I did the same thing for all my results.
Waitrose- 5.8 6.1 6.2 = 18.1. These results are reliable as the numbers are close.
Libby’s (original)- 7.0 7.5 7.1 = 21.6. Again the results are reliable as the numbers are close.
Just Juice- 8.0 7.5 7.7 = 23.2. These results are again reliable as the numbers are close.
Libby’s (organic)- 6.6 6.2 6.35 = 19.15. These results are accurate and reliable as the numbers are close.
Tesco- 7.8 7.1 7.6 = 22.5. These results aren’t very reliable mainly due to the anomalous result.
Del Monte- 7.0 7.1 7.5 = 21.6. These results are quite reliable as the numbers are relatively close.
Sunpride- 6.7 7.0 6.55 = 20.25. These results are close so they are reliable.
Sunny Delight- 8.9 9.0 8.95 = 26.85. These results are the most reliable as they are the closest together.
Overall my results are quite reliable.
I did further work with vitamin C tablets to see what kind of results I would get with them and to see if my method was as effective with something high in vitamin C. The tablets dissolved in water and I used 10ml for each experiment, the same amount as I used of juice.
These are my results
Experiment number DCPIP used
- 38.2
- 42.7
3 41.0
These figures are reliable and they also showed just how little vitamin c is actually in the orange juice compared to these. Obviously these tablets are used as supplements to people’s diets.
Therefore I believe that my results were sufficient to make a decent conclusion on this experiment. Extensions to this experiment could include using oranges rather then orange juice, from different countries and squeezing them until you have 10ml of juice then testing in the same way as the juice was and seeing which country produced the oranges with the most vitamin C. Another experiment could use different kinds of juiced of different fruits and seeing which fruit juice has the highest vitamin C content. This experiment could also be done in the same way but with vegetables to see which vegetables had the most vitamin C in them.
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