Biology Vitamin C

2056 Words Apr 11th, 2011 9 Pages
Investigating the vitamin C content of fruits and fruit juice

In this investigation, I aim to measure and compare whether there is a higher content of vitamin C in a fruit or a juice by measuring the volume of the sample required to decolourise a solution of dichlorophenolindophenol (DCPIP).

For this experiment, I aim to investigate and compare the content of vitamin C in the fruit against the fruit juice. The theory of this method is a titration with dichlorophenolindophenol (DCPIP). DCPIP is a redox dye and Ascorbic acid reacts with the DCPIP solution, changing the colour from a deep blue to either a pale pink or colourless solution. They react in a 1:1 state, so I can use the amount of ascorbic acid required to work
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The amount of DPCPIP solution used throughout the whole experiment will be kept constant, 5ml at a time. This is to prevent any errors or complications when working out the averages.

My dependant variable is the indicator, DCPIP, and the independent variables are both the grapefruit juice, and grapefruit.

Risk assessment & factors that can affect my experiment:
Knife safety – is slightly sharp so use with care
Wear goggles in case any of the grapefruit squirts in your eye whilst cutting
Take care with fragile glassware
Ascorbic acid is flammable, if inhaled could cause a sore throat. Irritant to skin and eyes for some.
The solutions may stain your skin and clothes so protective clothing will be useful.

Main apparatus: Quantity: | Apparatus: | Why and how it is used: | 45ml | DCPIP solution | It is a good indicator for vitamin C because if it’s present, the blue dye is reduced to a colourless compound by ascorbic acid.DCPIP reacts with ascorbic acid to turn colourless. When this occurs, the fruit juice being added will be stopped and noted down. | 10mg | Ascorbic acid | Also known as vitamin C. Is the dependant variable, so can be used as a focal point to see how much vitamin C is in a grapefruit and grapefruit juice. It will be used to see how much 'pure' vitamin C is needed to turn the DCPIP indicator colourless. When this happens, the amount of fruit juice used will be recorded. | 150mg | Grapefruit juice |

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