Summary:
In order to find out which past and present soft drinks have the most amount of vitamin c we must first react a sample of DCPIP solution with a vitamin c solution which has a known concentration. This then enables us to compare the strength of vitamin c in the soft drinks with that of a specific concentration.
The amount of vitamin c needed to decolourize a blue dye (DCPIP) by Experimenting with a variety of soft drinks.
Introduction
The aim of this experiment is to investigate how much vitamin c is needed to decolourize 1cm³ of a blue dye known as DCPIP (dichlorophenolindophenol). By experimenting with an old and new variety of lemon, orange and blackcurrant soft drinks we are able to find out which contains the most vitamin c from the amount it takes to decolourize 1cm³ of DCPIP.
Predictions
Vitamin c is a water soluble vitamin found in various fresh fruits and vegetables. The 'best sources of vitamin c are citrus fruits and their juices' . Fruits with high vitamin c content include lemons, peaches, strawberries, bananas and grapefruit. Vitamin c is involved in the repair of tissue damage and maintenance of healthy skin and blood vessels.
As vitamin c is at highest in citrus fruits I predict that the orange and lemon soft drinks will contain more vitamin c than the blackcurrant soft drink. Furthermore, as lemons are more acidic than oranges I would have to predict that the orange soft drinks will contain the most vitamin c.
Apparatus
The apparatus relevant to this experiment are:
Test tubes, a test tube rack, a glass rod to mix the solution, DCPIP solution, 5ml syringes and finally the various past and present soft drinks which are to be tested.
Variables
The independent variable in this experiment will be the soft drinks used as there will be a mixture of old and new flavours. This in effect will affect the dependant variable which is to measure how much soft drink is needed to decolourize DCPIP.
Method
In order to find out which past and present soft drinks have the most amount of vitamin c we must first react a sample of DCPIP solution with a vitamin c solution which has a known concentration. This then enables us to compare the strength of vitamin c in the soft drinks with that of a specific concentration.
To ensure that this is a fair test 1cm³ of DCPIP solution is to be used each time. Also every time a drop of soft drink is added to the DCPIP solution it needs to be stirred as this will enable an even distribution of the two solutions.
- Draw up 1ml of DCPIP solution into a 5ml syringe.
- Place the solution into a test tube and put it onto the test tube rack.
- Then draw up 5ml of one of the soft drinks into a 5ml syringe.
- Then add one drop at a time of the syringe with the soft drink solution in to the DCPIP solution.
- Stir the solution with the glass rod to ensure it is distributed evenly.
- This needs to be repeated until the DCPIP solution has completely decolourized.
The volume of soft drink remaining in the syringe needs then to be subtracted from 5ml to give the volume of solution added. The results then need to be recorded onto a table as this makes it easier to see which drinks have more vitamin c in if the results are all set out together.
Furthermore, for each soft drink I would recommend that the procedure above is to be carried out three times for each one and then an average worked out.
In addition, I would suggest keeping a different test tube for each solution, so that at the end of the experiment it is easier to make a comparison of the colour variations if any.
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