inki3
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Joined: Sat Oct 20, 2007 4:27 pm

Help please!

Postby inki3 » Sat Oct 20, 2007 4:40 pm

I would like to measure the amount of oxides in a fruit for a certain period of time until they perished, but I'm not sure how to measure the amount of oxides in fruits. Do I need any special equipment? I'd greatly appreciate it.

Thank You!

Louise
Former Expert
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Joined: Mon Jan 16, 2006 2:17 pm

Re: Help please!

Postby Louise » Sun Oct 21, 2007 6:43 am

inki3 wrote:I would like to measure the amount of oxides in a fruit for a certain period of time until they perished, but I'm not sure how to measure the amount of oxides in fruits. Do I need any special equipment? I'd greatly appreciate it.

Thank You!


Hi inki3,
I'm not sure what you mean by oxides? Are you talking about that brown that appears on the surface of a cut apple? Do you mean anti-oxidants or oxidants? Usually to measure the amount of a chemical in food, you do need special equipment. You should first identify exactly what chemical you want to test. [Note: oxide, anti-oxidants, and oxidants are not specific chemicals, but rather terms for groups of thousands of chemicals] For example, if you wanted to test the amount of vitamin c, you could do the titration described in this project:
http://www.sciencebuddies.com/mentoring/project_ideas/Chem_p044.shtml?from=Home

If you wanted to test for vitamin E, you would do a different test.

Why don't you think about what exactly you are trying to test, and what chemical you are really interested in and then post back. Included as much detail as you can. Also, let us know how old you are and if you've taken chemistry. Doyou have access to a chemistry lab at school?


Louise

inki3
Posts: 9
Joined: Sat Oct 20, 2007 4:27 pm

Postby inki3 » Sun Oct 21, 2007 9:18 pm

Thanks for your help Louise!
I'm currently a senior in high school and i've taken chemistry up to Chemistry 2 AP. I asked my chemistry teacher how I could measure it, but he didn't have a clue.

I wanted to measure the amount of antioxidants in a fruit for a certain period of time until it perishes! sorry for the vagueness...

How can I measure the amount of anti-oxidants in a fruit?

inki3
Posts: 9
Joined: Sat Oct 20, 2007 4:27 pm

Postby inki3 » Sun Oct 21, 2007 9:26 pm

OHH! i forgot to mention... i researched and i saw an article saying that the loss of phenolic compounds, ascorbic acid or flavonols is a trio of chemical classes associated with antioxidant content.

It's just a side not :]

Thank YOU!

Louise
Former Expert
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Joined: Mon Jan 16, 2006 2:17 pm

Postby Louise » Mon Oct 22, 2007 6:02 am

inki3 wrote:OHH! i forgot to mention... i researched and i saw an article saying that the loss of phenolic compounds, ascorbic acid or flavonols is a trio of chemical classes associated with antioxidant content.

It's just a side not :]

Thank YOU!


This isn't a side note- it is an important point! Someone did a similar project on tea. You should look through the thread and see what you think. This other project studies the phenolic type of compounds. Each "family" of compounds will have its own chemical test.

http://www.sciencebuddies.com/mentoring/phpBB2/viewtopic.php?t=2478&highlight=tea

Do you have access to a colorimeter or spectrophotometer?

Louise

inki3
Posts: 9
Joined: Sat Oct 20, 2007 4:27 pm

Postby inki3 » Mon Oct 22, 2007 8:16 pm

i have access to a spectrophotometer! I've read the link u posted it was huge help! But i'm still confused on the procedure and the chemicals i have to use for the spectrophotometer testing. I would like to find the presence of flavonols and ascorbic acid (vitamin C) and if possible phenolic compounds.

Thank You!

Louise
Former Expert
Posts: 921
Joined: Mon Jan 16, 2006 2:17 pm

Postby Louise » Tue Oct 23, 2007 6:05 am

inki3 wrote:i have access to a spectrophotometer! I've read the link u posted it was huge help! But i'm still confused on the procedure and the chemicals i have to use for the spectrophotometer testing. I would like to find the presence of flavonols and ascorbic acid (vitamin C) and if possible phenolic compounds.

Thank You!


I would narrow your project- this is a lot of work, especially since you want to repeat your measurements for accuracy. The link to the thread was for testing phenols and the link I gave earlier was for vitamin C. I'll review the tea thread again, and post back later. So, you have the procedures for 2 of the 3 tests, but maybe that is enough.


Louise

Louise
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Joined: Mon Jan 16, 2006 2:17 pm

Postby Louise » Tue Oct 23, 2007 9:39 am

The polyphenol assay is as follows:
"Total Flavonoid Content. The total flavonoid concentration wasmeasured using a colorimetric assay developed by Zhishen et al. (8,9). Briefly, 1 mL of appropriately diluted sample was added to a 10mL volumetric flask containing 4 mL of ddH2O. At time zero, 0.3 mLof 5% NaNO2was added to each volumetric flask; at 5 min, 0.3 mL of10% AlCl3was added; at 6 min, 2 mL of 1 M NaOH was added. Eachreaction flask was then immediately diluted with 2.4 mL of ddH2Oand mixed. Absorbances of the mixtures upon the development of pinkcolor were determined at 510 nm relative to a prepared blank."

Basically, the amount of light absorbed at 510 nm increases as the amount of flavanoid content increases. Please read _carefully_ the entire thread I posted; some of these chemicals (particularly the AlCl3) are dangerous. We discuss the safety in the other thread.


This procedure was taken from a paper vanillabean16 found; you should read the whole paper carefully.
http://72.14.209.104/search?q=cache:xZ4iVDFX_V4J:www.worldcocoafoundation.org/info-center/pdf/Lee.pdf+TEAC+assay+tea+antioxidants+and+milk+science+experiment&hl=en&ct=clnk&cd=2&gl=us

What you need to think about is how to get your solid fruit in to a solution form. You can probably take a set mass with water, and run it through a blender for a set time, and then filter out the solid. However, be aware that the chemicals you are interested in are degraded by contact with air, so this process could decrease the content of the vit. C and polyphenols just by exposing so many of the cells to air. This project would be better if you studied liquid; then you know your processing isn't destroying a bunch of chemicals.

Louise

inki3
Posts: 9
Joined: Sat Oct 20, 2007 4:27 pm

Postby inki3 » Tue Oct 30, 2007 9:18 am

Thank You Louise!
i've been researching for awhile and recieving advice from my teacher.
I intended to use liquid (by using blending machine and filtering out the solid) from fruit such as apple, orange, etc.
i was going to measure the amount of flavonoids and ascerbic acid. flavonoids would be measured through a spectrophotometer im able to attain. ascerbic acid would be measured by the process of titration. all the chemicals written in the procedure (as i've seen from the given link u gave me) are accessible. my chem teacher could get them for me easily.
so how does that sound? :]

Thank you always!

Louise
Former Expert
Posts: 921
Joined: Mon Jan 16, 2006 2:17 pm

Postby Louise » Tue Oct 30, 2007 9:42 am

inki3 wrote:Thank You Louise!
i've been researching for awhile and recieving advice from my teacher.
I intended to use liquid (by using blending machine and filtering out the solid) from fruit such as apple, orange, etc.
i was going to measure the amount of flavonoids and ascerbic acid. flavonoids would be measured through a spectrophotometer im able to attain. ascerbic acid would be measured by the process of titration. all the chemicals written in the procedure (as i've seen from the given link u gave me) are accessible. my chem teacher could get them for me easily.
so how does that sound? :]

Thank you always!


Sounds good to me, _but_ remember what I said about oxygen destroying these samples. The step with the blender introduces a lot of oxygen to a lot of surface area of the fruit. If you do choose to do this, controll this step as carefully as possible. All fruits should be 'blenderized'
(not a real word!) with the same total volume, same time, etc. Same with the filtration steps. Don't let one sample sit out for 5 minutes and one for 45.

Also, make sure you teacher understands the safety concerns for the procedure I gave you. The ascorbic acid (note spelling) titration is pretty safe, but the flavanoid experiment has some nasty chemicals in it.

Also, make sure your spectrophotometer works and can do the wavelength you need (510 nm) before you start!

Louise

inki3
Posts: 9
Joined: Sat Oct 20, 2007 4:27 pm

Postby inki3 » Sun Nov 04, 2007 8:00 am

OK! Thank You!
I'll let you know how things are going in my experiment~
:D

Louise
Former Expert
Posts: 921
Joined: Mon Jan 16, 2006 2:17 pm

Postby Louise » Sun Nov 04, 2007 8:54 am

inki3 wrote:OK! Thank You!
I'll let you know how things are going in my experiment~
:D


Great! Good luck!

Louise

inki3
Posts: 9
Joined: Sat Oct 20, 2007 4:27 pm

Re: Help please!

Postby inki3 » Tue Mar 11, 2008 4:36 pm

LOuise! or anybody else!
i ran into a problem...i have been conducting my research until now. I only have this week left before the deadline! my sodium nitrite disappeared and i cant find any local stores that sell sodium nitrite! is there any other chemical i could use? or any other way to test the amount of flavonoids in fruits using the spectrophotometer. !! Thank YOU!!

Louise
Former Expert
Posts: 921
Joined: Mon Jan 16, 2006 2:17 pm

Re: Help please!

Postby Louise » Tue Mar 11, 2008 5:51 pm

inki3 wrote:LOuise! or anybody else!
i ran into a problem...i have been conducting my research until now. I only have this week left before the deadline! my sodium nitrite disappeared and i cant find any local stores that sell sodium nitrite! is there any other chemical i could use? or any other way to test the amount of flavonoids in fruits using the spectrophotometer. !! Thank YOU!!


First, I'm _very_ concerned you lost this chemical. It can be dangerous (is a strong oxidizer and is poisonous- seriously poisonous- lethal dose is only a few grams, probably less for a child). You really need to find it. Where did you lose it, and what quantity of chemical was in the jar? Have you notified an adult? Some of the other chemicals also dangerous- these need to be in a secure location.

The safety sheet is here, which you should have already read:
http://www.jtbaker.com/msds/englishhtml/s4466.htm

This is EXTREMELY SERIOUS. Please post back here with the answers to the questions above, and please get help from an adult in finding this chemical. You need to talk to your science teacher about proper storage of the other chemicals- I seem to recall that the AlCl3 is also very nasty.

As to your scientific question:

Short answer- no.

Long answer- maybe. I read a bunch of literature procedures for the original thread. This procedure was the only one I found that did not require really exotic chemicals or equipment. It was also the only colorimetric method I ran across. So, while you probably could find another way, assembling the additional materials would take more time. It is possible that oxidizing agent would work, but you'd have to run a bunch of additional tests to make sure it did not alter the results. You probably don't have time to do this, plus you need to find your lost chemical for the reasons above.

Lastly, these forums don't provide instant answers. It can take up to 24-36 hours to get a response. I'm telling you this now, because I think you need to (quickly) involve an adult at your home or school in finding the missing chemical and devising an appropriate plan for the other chemicals. I do want to know about your search, and I will provide advice if I can, but you need help more rapidly than the forums permit.

Louise

inki3
Posts: 9
Joined: Sat Oct 20, 2007 4:27 pm

Re: Help please!

Postby inki3 » Tue Mar 11, 2008 10:30 pm

Thank you for your advice and help Louise!
I never took the chemical home. I left it in my chemistry teacher's room. I have talked about it with him and it just disappeared... I was concerned about it too. Also, the other chemicals were supplied by my teacher; this includes the AlCl3. I've never taken it out of the classroom. So it is a complete mystery. I have looked on all the drawers of the class except the storage room where my teacher keeps the chemicals and i'm not allowed in. The bottle was very small. it cost only about $15.
So the only problem I confront now...is to first find a sodium nitrite... and try to find this chemical somewhere in the room.
I must find this chemical.......

Thank you Louise!!!


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