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I need to compare the titrations of DCPIP, NBS and iodine to figure out the amount of vitamin C in a solution. Which is best and why?
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Igloo writes ...
 
I am assuming that you are using these titrations with fruit or vegetable extracts. Here are some ideas – though this is not intended as a comprehensive study.
 
The use of an iodine titration is the least satisfactory since iodine tends to oxidise other material within the samples as well as the vitamin C.
 
DCPIP is a better bet since it is a more discriminating oxidising agent and tends to target only the vitamin C. However, the end point is often rather indistinct.
 
The use of NBS is the most reliable technique since it specifically targets the vitamin C and, using iodide ions and starch as indicator, it gives the sharpest end-point.

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updated: 21 February 2008

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