Chapter 2 The nutrients in food
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I would like to know which indicator to use to determine the end point when titrating vitamin C.
The usual way to estimate vitamin C is to use the dye 2,6-dichlorophenoindophenol (dcpip). This is often called an 'indicator' but it is actually a coloured chemical that reacts with vitamin C.
You do not need another indicator because vitamin C reduces the blue dye which is then colourless. At the end point, on adding a slight excess of dye, you get a permanent blue colour.
You first standardise a dcpip solution by titration with a solution of vitamin C with known concentration, then you use the dcpip to estimate the concentration of unknown vitamin C solutions.
(See Nuffield Chemistry Food Science Special Study page 11.)
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Risk assessment
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updated: 27 November 2003
