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Old 04-23-2009, 03:03 PM   #11
pjj2ba
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Quote:
Author(s): Kac J, Mlinaric A, Umek A
Source: JPC-JOURNAL OF PLANAR CHROMATOGRAPHY-MODERN TLC Volume: 19 Issue: 107 Pages: 58-61 Published: JAN-FEB 2006
Times Cited: 3 References: 10 Citation MapCitation Map
Abstract: A sensitive thin-layer chromatographic method has been established for quantification of xanthohumol in hops (Humulus lupulus L.) and hop products. Chromatographic separation was performed on silica gel 60 HPTLC plates with toluene-dioxane-acetic acid, 77 + 20 + 3 (v/v), as mobile phase. The plates were scanned densito-metrically at lambda = 368 nm. The method was validated for precision, repeatability, and accuracy. It was found to be precise - intra-day and inter-day RSD were 1.7% and 2.3%, respectively. Instrumental precision and repeatability for the method were found to be 0.38 and 1.5 (%CV), respectively. The accuracy was checked by measuring the recovery at three levels; average recovery was 103.9%. The method was used for the estimation of xanthohumol in hop extracts and xanthohumol-enriched beer and was confirmed to be suitable for this purpose.
Here's a start. Its for an oil though, not an AA. I did find some perfect articles from '68 and '74, but the journal archives online don't go back that far - no abstracts either
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Old 04-24-2009, 07:30 PM   #12
Trouble-Brewing
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Quote:
Originally Posted by pjj2ba View Post
Here's a start. Its for an oil though, not an AA. I did find some perfect articles from '68 and '74, but the journal archives online don't go back that far - no abstracts either
Thats the problem I have been running into, seems like all the articles old enough to have simple technology are not available to me

 
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Old 04-25-2009, 06:01 AM   #13
celts
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a few options you might have are: 1) using the American Chemical Soceity website. They have a ton of good stuff that goes back ages. 2) if your school has SciFinder Scholar, you might want to try that. Again, great search engine. 3) your library might have an interlibrary loan program which allows you to get articles either via email or hard copy. I'll check my library tomorrow to see what we have access to.

 
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Old 04-25-2009, 06:05 AM   #14
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Well what have you tried? Did you try column chromatography or TLC?

 
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Old 04-26-2009, 06:20 PM   #15
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If you do try NMR, I can help you out a bit. The hydrogens directly next to the carbonyl on the relevent sidechain are the ones I'd look at.

Humulone will exhibit a ddqq pattern, with a big geminal splitting (16-18Hz). One of the doublets may go to an AB quartet depending on how much the chiral center affects it.

Cohumulone should have a qq pattern and integrate to 1H

Adhumulone is present in small percentages, but if isolated or concentrated will show a tq pattern.

I don't think you'd be able to discern cohumulone from colupulone, or adhumulone from adlupulone by this method. However Lupulone should lose one of the doublets from humulone because the chiral center is lost.

Below is an old scientific american article I came across while looking up the various molecules.

The Bitter Substance Of Hops

 
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Old 04-26-2009, 09:15 PM   #16
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Quote:
Originally Posted by celts View Post
a few options you might have are: 1) using the American Chemical Soceity website. They have a ton of good stuff that goes back ages. 2) if your school has SciFinder Scholar, you might want to try that. Again, great search engine. 3) your library might have an interlibrary loan program which allows you to get articles either via email or hard copy. I'll check my library tomorrow to see what we have access to.
I have not tried the chemical society website yet but my school has something similar to scifinder as well as the interlibrary loan program. Its just a matter of searching the right terms which apparently havent yet.

Quote:
Well what have you tried? Did you try column chromatography or TLC?
Nothing yet, I need to show my teacher an article before I can start

Quote:
If you do try NMR, I can help you out a bit.
Thanks. I am going to check that article out right now

 
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Old 04-27-2009, 05:28 AM   #17
Yeastie
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http://www3.appliedbiosystems.com/cm...cms_040396.pdf

or

Hop bitterness analysis

hope this helps. I find it stupid you need an article first, only being allowed to repeat something someone else did doesn't sound very groundbreaking or in the spirit of science.

 
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Old 05-01-2009, 03:32 AM   #18
Trouble-Brewing
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Quote:
Originally Posted by Yeastie View Post
hope this helps. I find it stupid you need an article first, only being allowed to repeat something someone else did doesn't sound very groundbreaking or in the spirit of science.
Yeah its not all that ground breaking but at least its not another experiment out of the boring lab book. The need for a paper is needed to prove to my teacher that I did isolate what I claim to

I did brew a small 2.5 gallon batch with some hop extract that I extracted from some pacific gems. Distilled 2 cups of cheap gin down to a cup of what should have been 80% ethanol and then boiled an ounce of crushed pac gems then filtered off the hops and washed them with warm water. To distill the gin I put a small bowl in the bottom of a pot on top of a metal measuring cup so it was off the heat a little. Then I put the gin in the bottom and the lid on upside down with ice on the top. Ethanol boiled up hit the cold lid and dropped into the cup. I put it in a simple pale ale, and added the extract at the beginning of the boil then added a half ounce of cascade in the last 5 min. I just tried it today and it came out pretty good, needs some more time to condition but definitely damn bitter.

 
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