[Kok Ming]

May I ask how to determine the Vitamin C concentration in pickled lime? Is that possible to determine the concentration of Vitamin C of pickled lime?

[Arkcon]

Its definitely possible, but it really depends on your technical level.  Let me ask you a question:  How have you determined the concentration of anything before?  What have you learned before, about tackling this sort of problem.  Let's see what you can come up with, so we can gauge your technical level, and we can see what we can work with.

[Kok Ming]

Thanks for your advise! Can I use below procedure to determine?
1. Add 25ml of standard Vitamin C solution and add 10drops of starch suspension.
2. Record how much iodine solution needed.
3. Make the pickled lime into juice then added with 10drops of starch suspension.
4. Record how much iodine solution needed.
5. Lastly, calculate the concentration of Vitamin C in pickled lime.

Basically, my procedure like this acceptable?

[Arkcon]

So you have everything you need (reagents, equipment, technical skill, knowledge) to perform a re-dox titration.  So the question now is: will anything in picked lime cause a problem?  I don't know.  Try it and see.  If you get no result, try spiking in some vitamin C standard, and see if you still get no result.  If so, then something in picked lime is blocking the reaction.  If not, then you know there isn't any vitamin C left over after pickling limes.

[Kok Ming]

Because my teacher say need oil in pickling the lime so the experiment is not valid. However in my point of view, pickling lime just need salt or sugar, so this can make into juice. May I ask if that can make into juice, the step I can determine Vitamin C concentration just like normal lime?

[Babcock_Hall]

Have a look at a chapter in the book Modern Experimental Biochemistry, 3rd edition, by Rodney Boyer.  He discusses the use of another redox indicator:  2,6-dichlorophenolindophenol.  He also discusses a way around the problem that other substances might also react in this assay.

[antimatter101]

Vitamin C is a reducing agent - it can actually reduce copper II to copper I by forming dehydroascorbic acid. You can use this method to test vitamin C concentration. Make sure that no chelating agents are present to affect the experiment.