Compare by means of investigation the vitamin C of a number of commercial and fresh fruit juices Measure the vitamin C content of a sample of fruit juice by measuring the volume of the sample required todecolourise a solution of DCPIP. Calibrate the results by comparison with a known concentration of vitamin C. ________________________________________
Demonstrate the effect of vitamin C on DCPIP. Get students to test 2 or 3 of the juices you provide to practise the technique. Ask students to develop a hypothesis to test, and to investigate it systematically. Your classroom organisation may depend on the equipment you have available. A burette of DCPIP may be the focal point for each working group. ________________________________________
For the class – set up by technician/ teacher:
Vitamin C solution, 1% (Note 1)
DCPIP solution, 1% (Note 2)
Fruit juice samples
The chemicals used in this investigation are LOW HAZARD (Notes 1 and 2). Read our standard health & safety guidance
1 Vitamin C solution: See CLEAPSS Hazcard. CLEAPSS Recipe card recommends a concentration of 0.1%; this protocol suggests 1%. This solution is LOW HAZARD. 2 DCPIP (2,6-dichlorophenol-indophenol) is LOW HAZARD; see CLEAPSS Hazcard. CLEAPSS Recipe card recommends a concentration of 0.1%; this protocol suggests 1% so dissolve 1.0 g of dye in 100 cm3 of water. ________________________________________
There are no ethical issues with this procedure. Consider what to do if your results give very different measures than those quoted by manufacturers. ________________________________________
SAFETY: Take care with fragile glassware such as burettes.
a Make up a 1% solution of vitamin C with 1 g of vitamin C in 100 cm3; this is 10 mg cm–3. b Make up a 1% solution of DCPIP.
c Pipette 2 cm3 of vitamin C solution into a test tube.
d Using a graduated pipette or a burette, add 1%...
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