- Volume and concentration of DCPIP
- Concentration of Vitamin C solution
- Extent of shaking of the test tube with DCPIP must be standardised
- Colour change of the DCPIP
- Temperature of the two solutions
- Volume of vitamin C needed to change the colour of 1 cm3 of DCPIP
- The type of Vitamin C
Prediction with science
Vitamins are complex organic molecules which are required by the human body, an example would be Vitamin C. This vitamin helps to regulate red blood formation, to absorb ions and fight against infections, however the most important function is an antioxidant.
This means that vitamin C helps to prevent the formation of radicals. During mitochondrial respiration, radicals are produces as a result of oxidation of water soluble molecules making a toxic byproduct with an unpaired electron. This then causes cellular damage, which can lead to damage of the endothelium with the possibility of triggering the start of atherosclerosis and then CHD. 
A function of Vitamin C is the stimulation of collagen which can help to undo the damage by the radicals which can trigger atherosclerosis. 
To detect the volume of Vitamin C found within the solutions we will be using Dichlorophenolindophenol (DCPIP). If vitamin C is present the blue dye is reduced to a colorless compound by ascorbic acid. This reaction is a redox reaction as vitamin C (ascorbic acid) is oxidized to dehydroascorbic acid, and DCPIP is reduced to the colorless compound DCPIPH2 
As Vitamin C is in many different types of drinks found in many supermarkets, I can make the prediction that the higher concentrations of vitamin C will be found in the more common drinks like Fanta and fresh orange.
Justifications of equipment
1% DCPIP Solution To test how much vitamin C is found within the drink in order for a colour change to occur
1% Vitamin C Solution To allow for comparison between different...