Investigating Vitamin C
Vitamin C is found in green vegetables, fruits, and potatoes. It is essential for a healthy diet. The chemical name for vitamin C is ascorbic acid. Ascorbic acid is a good reducing agent and therefore it is easily oxidised. Methods for the detection of vitamin C involve titrating it against a solution of an oxidising agent. Where to start
There are several oxidising agents that can be used and a commonly used one is 2,6-dichlorophenol-indophenol or DCPIP. You need to standardise this against a known concentration of vitamin C. This means finding out how much DCPIP reacts with a known amount of vitamin C. You can check the end point colour by testing a small amount of vitamin C with the DCPIP and observe the disappearance of the blue colour. The end point is usually a pink colour that persists for about 15 seconds or longer.
You will need to find out about the technique of titration and how to make up accurate solutions.
· Investigate the reliability of this method at different concentrations and under different conditions. You may also find slightly different procedures for the DCPIP analysis – are they more accurate/easier?
· Investigate other analytical agents such as iodine and Nbromosuccinimide. How do they compare to DCPIP?
· Investigate the stability of ascorbic acid under different conditions such as temperature, light and air/oxygen.
· Investigate the amount of vitamin C in foodstuffs and the effect of cooking them.
· It has been shown that vitamin C can interfere with the blue-black colour of the starch iodine complex. The vitamin C can turn it from blue-black to colourless. Investigate the possibility of using this reaction to determine vitamin C concentration.