testing for flavonoids in tea with milk. oh dear, help.

vanillabean16 · Post by **vanillabean16** » Wed Mar 14, 2007 6:42 pm

ok, i will make sure to double check the AlCl3 with my teacher. and i'll keep looking for that paper...
thanks!

Craig_Bridge · Post by **Craig_Bridge** » Wed Mar 14, 2007 6:44 pm

http://www.safety.duke.edu/msds/ProdPharmacy/AlCl3.pdf

Here is a Duke Medical Center Material Safety Data Sheet for a 30% aqueous solution of AlCl3 for reference.

This stuff is VERY corrosive! It is used in etching and plating processes and in a paste form for some exotic soldering processes. You defininately want to stay away from the anhydrous (powdered) forms because it is hard to contain while mixing and not end up everwhere!

Louise · Post by **Louise** » Wed Mar 14, 2007 7:49 pm

Craig_Bridge wrote:http://www.safety.duke.edu/msds/ProdPharmacy/AlCl3.pdf

Here is a Duke Medical Center Material Safety Data Sheet for a 30% aqueous solution of AlCl3 for reference.

This stuff is VERY corrosive! It is used in etching and plating processes and in a paste form for some exotic soldering processes. You defininately want to stay away from the anhydrous (powdered) forms because it is hard to contain while mixing and not end up everwhere!

The anhydrous form is also potentially explosive when in contact with water. It appears to be sold as anhydrous (solid), hexahydrous (solid), and as prepared solutions in benzonitrile and ethanol. I did not find a 10% solution in water that was availible. It would be best if you did not have to make the solution, since the solid form (esp. anhydrous) is much more dangerous. If you did, you would definitely use the hexahydrate form, which already has some (six) waters.

Some people I work with might use this stuff, so I want to ask around at work tomorrow. The MSDS is not too bad- this stuff isn't toxic or carcingenic, but this stuff is a strong base, and consequently, as Craig said, very corrosive.

Louise

vanillabean16 · Post by **vanillabean16** » Thu Mar 15, 2007 12:14 pm

so i was able to talk with my teacher today...
the spectrophotometer works! it did exactly what you said it should do. phew.
we have NaOH, but my teacher is going to order the AlCl3 and NaNO2. I mentioned to her what you said about the AlCl3 and we looked in the chemical book of the company from which the school orders, and it didn't mention any hazards.. so perhaps whatever they send out isn't as corrosive? But anyways, when i actually do the experiment she will be supervising.

she also mentioned that it would be a good idea to find a substance (such as HCl) that would be able to really clean the test tubes so that nothing interferes with the reading. I'm going to see what i can find out...

Louise · Post by **Louise** » Thu Mar 15, 2007 12:28 pm

Louise wrote:
Craig_Bridge wrote:http://www.safety.duke.edu/msds/ProdPharmacy/AlCl3.pdf

Here is a Duke Medical Center Material Safety Data Sheet for a 30% aqueous solution of AlCl3 for reference.

This stuff is VERY corrosive! It is used in etching and plating processes and in a paste form for some exotic soldering processes. You defininately want to stay away from the anhydrous (powdered) forms because it is hard to contain while mixing and not end up everwhere!
The anhydrous form is also potentially explosive when in contact with water. It appears to be sold as anhydrous (solid), hexahydrous (solid), and as prepared solutions in benzonitrile and ethanol. I did not find a 10% solution in water that was availible. It would be best if you did not have to make the solution, since the solid form (esp. anhydrous) is much more dangerous. If you did, you would definitely use the hexahydrate form, which already has some (six) waters.

Some people I work with might use this stuff, so I want to ask around at work tomorrow. The MSDS is not too bad- this stuff isn't toxic or carcingenic, but this stuff is a strong base, and consequently, as Craig said, very corrosive.

Louise

Okay, I meant to say "acid" above (it is a lewis acid), not "base". I found one person who worked with the anhydourus stuff, which you definitely don't want to do.

NaOH is a strong base (this time, I really do mean base). You need gloves, long sleeves, googles and preferably a hood to to these reactions. You need to follow the procedures very carefully (the full procedure, not the brief version) and you should have a mentor assisting you.

I don't think this is beyong your level. I did my 11th grade science fair project on a similar level of chemical difficulty (and danger- using strong acids and bases), and my chemistry teacher let me work in the lab on Saturday's while he was there. He also approved my procedure so everything was safe.

Louise

vanillabean16 · Post by **vanillabean16** » Thu Mar 15, 2007 2:04 pm

what do you mean by the "full" procedure?

Craig_Bridge · Post by **Craig_Bridge** » Thu Mar 15, 2007 5:35 pm

I suspect that Louise meant for you to find the "full" text of the experimental write up that describes the experimental proceedure fully and not just an abstract that glosses over the details (the things that people who have done it before might understand, but somebody new to the process has no clue that there is more to it).

Louise · Post by **Louise** » Thu Mar 15, 2007 7:35 pm

Craig_Bridge wrote:I suspect that Louise meant for you to find the "full" text of the experimental write up that describes the experimental proceedure fully and not just an abstract that glosses over the details (the things that people who have done it before might understand, but somebody new to the process has no clue that there is more to it).

Your paper says something like "We followed the procedure of these other authors (references 8,9). In brief, this is what we did..."

So, the "in full" part, should be in the references 8 and 9. It is like me saying, "I made a pound cake, using lemon extract and whole wheat flour". A cook who knew the recipe for pound cake could make my cake (and would know how I modified the procedure). But, if you've never made a pound cake, or seen a recipe for one, you'd be lost. Since we've never seen the full "recipe" for this procedure, we have no idea how much detail is omitted. Additionally, good papers provide information about the dangers and things that can go wrong, which is very useful.

Louise

vanillabean16 · Post by **vanillabean16** » Sat Mar 17, 2007 9:18 am

Well, i sent the reference to the hospital library with my father to get the full text that's not available online... and somehow he managed to get completely different articles...
is there any other way to get ahold of that article? I would ask him to look for it again but he's actually leaving the country for the next 10 days so he won't be able to help me.

Thanks again.

Louise · Post by **Louise** » Sun Mar 18, 2007 10:35 am

vanillabean16 wrote:Well, i sent the reference to the hospital library with my father to get the full text that's not available online... and somehow he managed to get completely different articles...
is there any other way to get ahold of that article? I would ask him to look for it again but he's actually leaving the country for the next 10 days so he won't be able to help me.

Thanks again.

Please post the references here and I will look for them.

Louise

vanillabean16 · Post by **vanillabean16** » Sun Mar 18, 2007 4:46 pm

i actually found it. the procedure is pretty much the same.. except there is one problem! The replicated procedure calls for 0.3 mL NaNO2 and 0.3 mL of AlCl3. The original calls for the same of NaNO2, but for 3 mL AlCl3. and everything else is absolutely the same.
Which volume should i go with?!
and now for some questions..

what does 2 mL of 1 M NaOH (also written 2 mL 1 mol liter^-1 NaOH) mean?
Also, how much milk should be added to each tea sample? The tea is brewed in 200 mL distilled water (about 3/4 cup), so i was thinking a tablespoon or two? That seems to be about average..

thank you, as always.

vanillabean16 · Post by **vanillabean16** » Sun Mar 18, 2007 4:54 pm

i just thought to mention that in the original procedure they are not testing tea, they are testing dried mulberry leaves.. i don't know if that makes any difference.
also, the procedure says "AlCl3 was added 5 mins later. After 6 mins, NaOH was added.." so does this mean that 1 minute after the AlCl3, the NaOH was added, or 6 minutes after?
i'm sorry to ask so many questions! but you guys are very helpful.

Louise · Post by **Louise** » Sun Mar 18, 2007 4:58 pm

vanillabean16 wrote:i actually found it. the procedure is pretty much the same.. except there is one problem! The replicated procedure calls for 0.3 mL NaNO2 and 0.3 mL of AlCl3. The original calls for the same of NaNO2, but for 3 mL AlCl3. and everything else is absolutely the same.
Which volume should i go with?!
and now for some questions..
what does 2 mL of 1 M NaOH (also written 2 mL 1 mol liter^-1 NaOH) mean?
Also, how much milk should be added to each tea sample? The tea is brewed in 200 mL distilled water (about 3/4 cup), so i was thinking a tablespoon or two? That seems to be about average..

thank you, as always.

Give me the other reference, and I'll see if I can find out what the reaction is and why NaNO2 is important. Then I will see why there is such a large difference in volume. (Sounds like someone made a typo to me)

molar is a method of specifying concentration. It is number of moles/volume, where moles is mass used/ molecular weight. What form is your NaOH in? If you have a solid, we can make some 1 M NaOH. I will show you how to do the math. If you have a solution of NaOH already, it will either be labeled in Molar Units (1 M, 10 M, whatever) or in Normal units which is abbreviated as N. In this case, they are the same. So, 1 N sodium hydroxide (NaOH) is the same as 1 M NaOH.

Louise

vanillabean16 · Post by **vanillabean16** » Sun Mar 18, 2007 8:06 pm

the other reference is not available online.. i had to have it printed from the hospital library, and i only have a text copy of it. it doesnt mention the chemicals that were used anywhere else in the lab other than the methods..the only thing it talks about is the OH and O2 scavenging properties of flavonoids. It says..
"It is suggested that the overall antioxidant effect of flavonoids on lipid peroxidation may be related to their OH and O2 scavenging properties and their reaction with peroxy radicals. Thus, O2 may play an important role during the perodixation of unsaturated fatty acids and possibly other susceptible substances. Therefore, the study of the scavenging effects of antioxidants on O2 is one of the most important ways of making clear the mechanism of antioxidant activity and has therefore caused growing interest among researchers. Flavonoids can be used directly to scavenge O2 and OH by single electron transfer. The scavenging process can generally be followed by means of electron spin resonance... The photochemical reduction of riboflavin was first used to determine the dismutation of O2 by superoxide dismutase (SOD) and has been adapted for analysis of the dismutation of O2 by a model compound of superoxide dismutase and other natural compounds."
and thats it for useful information! The rest is just background... rather useless, actually.
So maybe that is where the NaOH and NaNO2 come in, to be targets for OH and O2 "scavenging", and the AlCl3 causes color to appear?

and i do believe that the NaOH we have is in solid tablets.. i certainly hope my teacher will know how to concentrate it correctly.. but it wouldn't hurt for me to know as well!

i hope that exerpt from the lab helped maybe a little.. thats really all there is about flavonoids, as the rest of the lab tested the scavenging of superoxide radicals and used an HPLC.

:)thanks[/img]

Louise · Post by **Louise** » Mon Mar 19, 2007 6:53 am

vanillabean16 wrote:the other reference is not available online.. i had to have it printed from the hospital library, and i only have a text copy of it. it doesnt mention the chemicals that were used anywhere else in the lab other than the methods..the only thing it talks about is the OH and O2 scavenging properties of flavonoids. It says..
"It is suggested that the overall antioxidant effect of flavonoids on lipid peroxidation may be related to their OH and O2 scavenging properties and their reaction with peroxy radicals. Thus, O2 may play an important role during the perodixation of unsaturated fatty acids and possibly other susceptible substances. Therefore, the study of the scavenging effects of antioxidants on O2 is one of the most important ways of making clear the mechanism of antioxidant activity and has therefore caused growing interest among researchers. Flavonoids can be used directly to scavenge O2 and OH by single electron transfer. The scavenging process can generally be followed by means of electron spin resonance... The photochemical reduction of riboflavin was first used to determine the dismutation of O2 by superoxide dismutase (SOD) and has been adapted for analysis of the dismutation of O2 by a model compound of superoxide dismutase and other natural compounds."
and thats it for useful information! The rest is just background... rather useless, actually.
So maybe that is where the NaOH and NaNO2 come in, to be targets for OH and O2 "scavenging", and the AlCl3 causes color to appear?

and i do believe that the NaOH we have is in solid tablets.. i certainly hope my teacher will know how to concentrate it correctly.. but it wouldn't hurt for me to know as well!

i hope that exerpt from the lab helped maybe a little.. thats really all there is about flavonoids, as the rest of the lab tested the scavenging of superoxide radicals and used an HPLC.

:)thanks[/img]

Just give me the citation for the paper. I work at a University, so I can get it online.

Oh, and I think 1-2 T of milk is fine. If I put milk in my tea (black, not green), I usually put in 2 T.

Louise