Naked Science Forum

General Science => General Science => Topic started by: VickiLacey on 17/06/2008 14:32:57

Title: How is vitamin C concentration measured?
Post by: VickiLacey on 17/06/2008 14:32:57: I am doing a research project in college looking into vitamin C deterioration in fresh orange juice. I have been diluting the orange juice with distilled water and acetic acid then titrating this dilution with DCPIP. The only thing is I am unsure of why I am using acetic acid. What does this do to the vitamin C? Why is it necessary for this titration? Can anyone help?? [:)]
Title: Re: How is vitamin C concentration measured?
Post by: blakestyger on 18/06/2008 12:25:28: It is usual with vitamin C determinations in plant (and animal) tissue to use a dilute solution (ca. 9%) of acetic acid to act as a tissue extractant. It is not actually reacting with the vitamin C itself.
Title: How is vitamin C concentration measured?
Post by: iko on 18/06/2008 13:54:09: Quote from: blakestyger on 18/06/2008 12:25:28
It is usual with vitamin C determinations in plant (and animal) tissue to use a dilute solution (ca. 9%) of acetic acid to act as a tissue extractant. It is not actually reacting with the vitamin C itself.

I knew that 10% trichloracetic acid (TCA) 1:1 denaturates proteins and stabilizes ascorbic acid by its strong acidity. This is a standard procedure for serum/plasma.
Then samples can be stocked at 4-8°C for weeks, protected from light until tested.
HPLC technology or old (Roe et al.1941) clinical chemistry methods can be used.
By HPLChromatography ascorbate and dehydroascorbate can be measured easily enough.
Title: How is vitamin C concentration measured?
Post by: RD on 19/06/2008 11:22:35: Fab and groovy pics for the cover of your Vit C report...

http://www.sciencephoto.com/images/imagePopUpDetails.html?pop=1&id=656120290&pviewid=&country=67&search=vitamin+AND+c&matchtype=FUZZY

http://www.sciencephoto.com/images/imagePopUpDetails.html?pop=1&id=656120287&pviewid=&country=67&search=vitamin+AND+c&matchtype=FUZZY

http://www.sciencephoto.com/images/imagePopUpDetails.html?pop=1&id=656120260&pviewid=&country=67&search=vitamin+AND+c&matchtype=FUZZY
Title: How is vitamin C concentration measured?
Post by: VitaminC on 16/09/2010 06:16:46: All I can think of is the acetic acid is acting as a buffer for the vitamin C, they have similar pKa values.
Title: How is vitamin C concentration measured?
Post by: Bored chemist on 16/09/2010 06:50:04: Did you see the date of the original question?
Title: How is vitamin C concentration measured?
Post by: benjamin1greer on 16/09/2010 08:08:44: Measure the vitamin C content of a sample of fruit juice by measuring the volume of the sample required to decolourise a solution of DCPIP. Calibrate the results by comparison with a known concentration of vitamin C.
Title: How is vitamin C concentration measured?
Post by: Bored chemist on 16/09/2010 19:10:40: Did you really think that helped?