Aim:To compare the vitamin C content of different fruits using the decolourisation of DCPIP from blue to clear as the indicator.
•You first need to estimate the volume of a known concentration of vitamin C solution required to decolourise 2 cm3 of DCPIP solution.
•Then you need to determine the volume of fruit juice that decolourises 2 cm3 of DCPIP solution. This gives an estimate of the concentration of vitamin C in fruit juice.
•This value is then multiplied by the volume of the fruit to obtain its total vitamin C content.
50 cm3 beaker
100 cm3 beaker
500 cm3 beaker
250 cm3 measuring cylinder
Pipette to measure 2 cm3
Pipette to measure accurately up to 1 cm3
Test tubes x 2
Vitamin C solution (0.1%)
DCPIP solution (1% aqueous)
Various fruits and vegetables
1.Measure 2 cm3 of DCPIP solution into a test tube.
2.Using a pipette, add vitamin C solution, drop by drop, to the same test tube.
3.Shake the tube gently after the addition of each drop.
4.Continue until the DCPIP solution is decolourised.
5.Record the exact volume of vitamin C you added.
6.Repeat and average your results.
7.Calculate the mass of vitamin C that is required to decolourise 2 cm3 of DCPIP, knowing that the vitamin C solution was made up to contain 1mg per 1.0cm3 of water.
8.Repeat the procedure using the fruit juice provided.
9.Using the same technique compare the vitamin C content of several fruits and vegetables.
10.To determine the volume of the fruit, place it in a beaker and cover with water.
11.Mark the level of the meniscus on the outside of the beaker.
12.Remove the fruit and make the water up to the mark with water from a measuring cylinder. The volume of water added is the volume of the fruit.