Testing juice for vitamin C

[winstonplatt]

I hope this sort of question is allowed on this forum.

 

Im in high school and I'm going to be writing an science paper soon, "APA" style.

 

As I topic Iv decided to test for vitamin C in various juices. I plan on seeing how the amounts change over time, both refrigerated and unrefrigerated.

 

Questions:

1. Are there other chemicals that could easily be tested for in juices? I need plenty of data to write 2,000 words.

2. Whats the best method for testing vitamin C in juices? I need something that will be able to test for small changes. There seems to be two methods Iv found: chemical test strips, and titration using iodine and startch. Strips: http://www.naturamart.com/perque-perque-c-strips-100-strips.html

Titration:http://www.life.uiuc.edu/boast1/sciencelessons/vitaminc.htm

3. Should I even expect Vitamin C levels to change much over time at room temperature? If not, any advice?

 

 

Thanks!

[UC]

2. The iodine/starch titration is going to be the most accurate determination technique by a wide margin. Titration is a skill and if you haven't done it before, you should practice at least a few times.

[winstonplatt]

What sort of percentage-difference in vitamin C would there have to be for it to detect a difference?

 

More in the range of 5% or 20%? Just asking for a rough guess since you probably haven't done his particular titration.