1.14 Flashcards
what reagent do you have to use to test for vitamin C
DCPIP (2,6-dichlorophenol-indophenol)
What is the aim of this experiment?
investigate the different Vitamin C content in different fruit juices
What is the independent variable of the experiment?
Type of fruit juice
What is the dependent variable?
Volume of juice required to decolourise 1cm3 of DCPIP
What are the control variables?
- Temperature
- Concentration of DCPIP
- Volume of DCPIP (1cm3)
- Shake tube same number of times
- same end point colour
What’s the colour of the reagent solution?
blue
What happens when DCPIP reacts with vitamin C
it turns colourless (although in very acidic solutions it may turn pink)
what do we do if the food to be tested is a solid?
make an extract
How do we make an extract?
Crush and chop a small amount and put it into a test tube to a depth of about 2cm. Add a similar amount of distilled water and stir with glass rod. Then allow to stand for a few minutes.
what equipment is required to carry out this experiment?
- DCPIP solution
- Vitamin C solution
- Different fruit juices
- Test tubes
- Conical flasks
- pipette
- burette
What result in the experiment does shaking too much have?
adds oxygen which will slightly restore the DCPIP to blue (systematic error)
Explain the correlation shown in this experiment?
You should see that as the vitamin C content increases, the volume required to decolourise the DCPIP decreases; a negative correlation.
How many methods of doing this experiment are there?
2 methods
what two equations are required to measure the vitamin C content?
Mass of vitamin C to decolourise 1cm³ of DCPIP =
10mg × volume of vitamin C used
Mass of vitamin C in fruit juice sample =
mass of vitamin C to decolourise 1cm³ of DCPIP × volume of sample required to decolourise 1cm³ of DCPIP
