Science Buddies: "Ask an Expert"

How can I measure the malic, citric, and ascorbic acids of an orange separately?
Can you suggest any titration or neutralization methods that would allow me to measure them. I am investigating the effects of malic and citric acids on the retention of vitamin C in oranges under varying storage conditions. I know that I can use iodine and count the number of drops to determine relative quantity of vitamin C. I don't know how to measure the relative amount of malic or citric acids. Please help.

Hi,

Most people who need to determine the amounts of ascorbic, citric, and malic acids in one sample use some form of liquid chromatography to separate them, then measure them. Here is a book exerpt that discusses the issue:

http://books.google.com/books?id=1c9dq_ ... #PPA477,M1

I am sorry that this article is rather difficult to read for a person at your grade level, but you can get simpler explanations of the words used by using google (www.google.com) to search for the words you want to understand. I am sorry that I do not have a simple experiment to offer you that will allow you to individually determine these acids separately in an orange. If you want to attempt this experiment you would likely be most successful if you can find a chemist friend who has access to HPLC (High Perfomance Liquid Chromatography) equipment, who can help you do the experiment.

You sound like you have a strong interest and talent for chemistry . I wish you every success in your project.

Best regards,

Barrett Tomlinson