Use equal masses and a standard extraction method, add sample to a known DCPIP volume until decolourised and calibrate or calculate before comparing foods.
Vitamin C is an antioxidant.
The concentration of vitamin C in a variety of locally sourced and imported fruits was measured.
Describe how vitamin C content in an extract of a fruit can be measured.
A description that includes four of the following:
- use of DCPIP (1)
- use known volume DCPIP (1)
- add \{extract / stock Vitamin C\}until no blue colour remains / becomes colourless / decolourises (1)
- record volume of \{extract / stock Vitamin C\}used (1)
- do titration again with (stock Vitamin C / extract) (1)
- compare the volume of extract added with the volume of stock added / stated correct equation to calculate Vitamin C content
accept titration of DCPIP into extract in mps 2, 3, 4 and 6
accept other appropriate redox dyes throughout, e.g. methylene blue
ignore add drops ignore amount
accept known Vitamin C concentration = stock
accept known Vitamin C concentration = stock
concentration of vitamin C in fruit juice = volume of standard solution added ÷ volume of fruit juice added x concentration of standard solution V1C1=V2C2
Expert (4)