Conclusions and Evaluations
Drawing on the background research this experiment shows that grapefruit juice contains the most vitamin C out of the fruits tested so it would be preferable to drink. This is because it can work as an antioxidant to protect your DNA from free radical damage. Also it can help you body produce collagen for healing. Therefore grapefruit juice would be a useful additon to a healthy lifestyle
The null hypothesis was that the juices would have no significant difference in vitamin C content compared to grapefruit juice. The results themselves show there is a difference in the vitamin C content. The statistical tests confirm this. Each time it shows there is more than a 20% significant difference between the juices. This means that the null hypothesis is wrong as the juices had significantly different amounts of vitamin C in them. My null hypothesis is rejected. But the experiment still gave good results and showed which juice contains most vitamin C. Which will be most beneficial to our bodies.
However the results may not be completely correct due to errors made during the experiment. The first possible error to take into account with any titration is a parallax error. This is an error where you don't look at the burette at eye level. This means the value will look different to what it is. Another possible form of error is quantative errors. These are errors could be for example the amount of the solutions being different. This could happen through spillages or not using the measuring equipment properly to ensure you have the correct amount. One error this experiment could have is that it is sometimes hard to tell exactly when the solution turn from blue to purple as the change is subtle.
The juice itself could have affected the results. By not using fresh fruits we dont know what additives there could be in the juice. The supermarket juice could contain artificial vitmain C and preservatives that could have affected the results of the experiment.
To ensure these errors are avoided always look at the burette at eye level to ensure the value recorded is correct. Also ensure all the solutions are properly measured out as accurately as possible to minimise the inaccuracy of results. When it comes to seeing the colour change the only thing to do is keep stopping the titration and carefully looking at the colour. Then adding theDCPIP dropwise should minimise the risk of adding an excessive amount. Using freshly squezzed juices was to slow but may have made the results more accurate.
The null hypothosis was chosen over other similar hypothesis' because it was easy to test and analyse. It was also chosen as other similar hypothesis' may not have been economical or feasible in a college environment. For example a hypothosis that could have been chosen was "Every fruit has a different amount of vitamin C". This may be true but would take hours to test and would cost a lot of money. The reason grapefruit juice was stated to have the same amount of vitamin C as the other was because a null hypothesis states there is no significant difference between the juices.The main reason it was chosen was because it was an interesting easy topic to research and the results gained from it could benefit a healthy lifelstyle.The results of the experiment rejected the hypothesis
Throughout planning and carrying out the experiment ther was many things to consider. More than one approach was considered to try and maximise the accuracy of the results obtained from the experiment. As shown in the week by week planning the first approach taken was not time efficient and did not work very well due to the consistancy of the juice. The only other problem that arose was during the statistical testing where the wrong statistical test was used but this was easily and quickly corrected .With this experiment there was no economic restraint as the only cost was the fruit juice and the DCPIP.
FRAP assay (Ferric Reducing ability of plasma) is a method of measuring the amount antioxidant potential in something. A reagent made from acetate buffer, tripyridyltriazine and iron chrolide is used for this method of finding the concentration of vitamin C. This reagent is a FRAP reagent. When mixed with vitamin C solutions or juices the antioxidents in the juice reduce the ferrric ions in the iron chloride. When the pH is low the tripyridyltriazine works with the ferriois ions and a blue colour is produced. The more antioxidant in a solution the more ferrious-tripryidltriazine complex is formed so the colour produced is a deeper blue.The absorbance rate of the test subject is measured using a spectophotometer at 593nm. These results can then be comapared to known samples of increasing concentration. This means you can compare the gained results on a graph showing the standard curve of results. So this experiment would work for testing the concentraion of vitamin C in a solution and would likely give much more reliable results than a titration. The FRAP assay experiment is not expensive and is easy to carry out but requires some more expensive equipment like a spectophotometer. However this test gives results that are reproducible and can therefore be more relied upon than a titration.
Carrying out a redox titration may have been batter than carrying out an acid based titration. This is because fruit juices have acids in them already and so this may effects acid based titrations. Where as a redox titration is carried out using iodine and the solution being tested turns a blue black colour to indicate that all of the vitamin C has been oxidised. This titration could have been carried out and may have been better as the acids in the juices would not have affected the results as much. Also i feel that the colour change would have been more dramatic meaning it would have been easier to tell when all the vitamin C had been oxidised.
Howver this experiment worked well and gained accurate enough results to analyse to determihne the amount of vitamin C in different shop bought fruit juices and considered the health benefits of drinking juices high in vitamin C. The results however were not valid enough and do not compare well with published data. this is likely due to the previously stated errors. The results gained in the experiment would not be put onto the juice cartons as a guide to how much vitamin C is in the carton of juice as the results were clearly incorrect due to many different factors. The statistical tests in particular show how much the expected values differ from those obtained from published data. If given the chance to reconduct an experiment into finding the amount of vitamin C in a solution i would chose one of the other methods and replicate the experiment may times to gain the most acurate results possible.
