Science Buddies: "Ask an Expert"

I'm a dad working on a science fair project with my son. He is examining the effect of temperature on Vitamin C concentration in solution (Fruit Juices, Diluted Vit C Tablet, etc.)

We thought there was a Vit C test kit available, which turned out to fall through.

We need a method to test for a change in Vit C Concentration. Is there a detailed procedure, kit or other suggestion anyone is aware of?

I have a couple semesters college chem and he is in 8th grade. We need to complete the experiment within a couple weeks.

Thanks for your help.

Hi,

Here are two websites that describe procedures for measuring vitamin C based on the oxidation of ascorbic acid to dehydroascorbic acid. The first site does not explain how to make the starch, or the iodine solution, but the second website has enough detail to prepare the solutions.

http://chemmovies.unl.edu/chemistry/bec ... BD047.html

http://www.ivygreen.ctc.edu/knutsen/che ... aminc.html

There is a simpler method using titration with a color indicator, 2,6-dichloroindophenol, based on the same oxidation reaction.

Here's a website that describes how to make this reagent:

http://www.colby.edu/chemistry/PChem/la ... corbic.pdf

You would probably need to obtain the reagents from a lab supply company, so your decision on which method to use would probably depend on the availability of the chemicals.


I hope this will help!

Donna Hardy

Hi!

Here are some websites that will help (hopefully ):

1. http://www.nutri.com/strips/ (buy C-strips)
2. http://www.alumni.ca/~walkerd/sf2.html (titration)
3. http://www.selah.k12.wa.us/SOAR/SciProj2002/AnnieM.html (similar experiment)
4. http://www.life.uiuc.edu/hughes/boast/s ... taminc.htm (titration and how to perform titration)

Hope these sites help!

Hi Bill,

The C-strips described in the first website Jessica suggested contain the dichoroindophenol indicator I suggested. This appears to be the simplest way to measure vitamin C. However, I can't tell if these strips are quantitative or not. You might have to adapt the protocol with the strips to obtain an exact concentration of vitamin C.

In the background section of the science fair project, be sure you son explains the chemistry behind the vitamin C analysis. The vitamin C is oxidized to dehydroascorbic acid and the dicholoroindophenol is reduced from the blue to the colorless form. Your son hasn't had chemistry yet, but he should be able to explain what is happening to a certain extent. Is there anything in your samples that can interfere with this reaction?

In the experiment, have your son verify that the only variable in the experiment is temperature. All other parameters (light, oxygen, time, etc) should be controlled (identical).

Let us know if you have any other questions. Good luck!

Donna Hardy

Thanks to you both of you for your suggestions.

Donna, I appreciate the sites as well as the lead on the strips. I also appreciate the words of caution and will make sure that my son understands what is happening prior to the experiment. Great opportunity to learn some basic chem.

Jessica, I appreciate the sites you provided as well. Great samples of possibilities. We will be pouring through all the sites over the next few days and hope to move the project forward quite a bit as a result.

Any other thoughts or additional sites anyone can suggest would be appreciated.

Thanks again for the help!