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Old 08-16-2011, 06:16 AM   #11
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I assume you are using a spectrometer to measure this stuff...where did you get one that you can just do this stuff at home?

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Old 08-16-2011, 12:33 PM   #12
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The one I have was actually made by Beckman but for Hach (the water analysis people) from whom I bought it.

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Old 08-16-2011, 01:03 PM   #13
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I assume you are using a spectrometer to measure this stuff...where did you get one that you can just do this stuff at home?
I traded a function generator for it (I have a lot of idle / redundant equipment at home). I also have unlimited access to another spec (that I use for UV already) and a UV power meter and thermopile. I need to trade something for some chemicals and a little knowhow
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Old 08-16-2011, 01:40 PM   #14
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The know-how is free. You can get it here. It would be best,however, if you got a copy of the MOA. ASBC now publishes an abbreviated set of MOA's for craft brewers at a price which is much more reasonable than the full set (which is only available on line at this point anyway). If you don't want to buy those or can't find them I can go through the procedure in detail here. It's not really complicated at all for someone familiar with how to use a spectrophotometer.

There is one clunker in there though. After putting beer, acid and iso-octane into a 50 mL centrifuge tube it has to be shaken vigorously for 15 minutes. This can be done by hand (I even met a guy who does this for a living shaking by hand) but a mechanical shaker (it's obvious from the MOA that ASBC had Burell in mind) makes life much easier if you intend to do many anyalyses.

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Old 08-16-2011, 03:47 PM   #15
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The know-how is free. You can get it here. It would be best,however, if you got a copy of the MOA. ASBC now publishes an abbreviated set of MOA's for craft brewers at a price which is much more reasonable than the full set (which is only available on line at this point anyway). If you don't want to buy those or can't find them I can go through the procedure in detail here. It's not really complicated at all for someone familiar with how to use a spectrophotometer.

There is one clunker in there though. After putting beer, acid and iso-octane into a 50 mL centrifuge tube it has to be shaken vigorously for 15 minutes. This can be done by hand (I even met a guy who does this for a living shaking by hand) but a mechanical shaker (it's obvious from the MOA that ASBC had Burell in mind) makes life much easier if you intend to do many anyalyses.
Lab Methods for Craft Brewers is $140 on Amazon. If I intended on taking this much further than a weekend experiment, I'd buy that. If I decide to go further and do a lot more analysis, it's a no brainer.

But right now I'm just looking for some fun between brew days. So, yes AJ, if you wouldn't mind detailing this one test, I'd appreciate it. The links I posted above have some broad strokes; I suspect you have further detail for a non-chemist like me. Thanks.
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Old 08-16-2011, 05:36 PM   #16
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Didn't think the book was that expensive!

What you need:

1. Spectrophotometer with UV capability
2. Quartz cuvets (expensive)*
3. 10 mL disposable pipets
4. 50 mL centrifuge tubes
5. Spectrographic grade 2,2,4 trimethyl pentane
6. 3 N hydrochloric acid
7. Octanol
8. Wrist action shaker (Burell) or wrists with good action
9. Centrifuge.
10. Pipetter (bulb) for 10 mL pipets
11. Smaller pipetter and tips

What you do:

1. Place a sample of cold, carbonated beer in a small beaker or glass
2. Dip the tip of a 10 mL pipet into octanol. Withdraw it and shake the alcohol off the end. A wee bit will remain and that's what you want
3. Lower the pipet into the beer and draw up 10 mL. The octanol will keep it from foaming so you can read the level accurately
4. Pipet into a 50 mL centrifuge tube
5. Pipet in 1 mL 3 N hydrochloric acid
6. Pipet in 20 mL 2,2,4 trimethyl pentane (use a new 10 mL pipet twice or if you have a 20 mL pipet use that).
7. Cap tube and shake vigorously for 15 minutes preferrably on a shaker
8. While extraction is taking place (do this and the next step before everything else if you are shaking manually) dip a toothpick or micropipet tip into octanol, shake off and touch to the inside of your blank cuvet.
9. Pipet 2 or so mL 2,2,4 trimethyl pentane into blank cuvet. Invert to mix.
10. At the conclusion of extraction remove tube from shaker and examine. There will be 1, 2 or 3 phases. One is the beer, the second, which may or may not be present, is a sort of slush. The third is clear solvent which should be on top and separate from the second. If it is skip to Step 12
11. Centrifuge at top speed** for three minutes to separate second and third phases.
12. Pipet 2 or so mL of the clear 3rd phase into the sample cuvet.
13. 0 photometer at 275 nm using the blank cuvet.
14. Read absorption at 275 nm for the sample cuvet.
15. Multiply absorption by 50 e.g if A275 = 0.500, the IBU = 25

*There are plastic disposable cuvets that claim decent transmission into the UV. Much less expensive, of course, but I've never tried them.
As the iso octane is quite volatile and as many of the less expensive instruments have lots of plastic parts (and even caveats against the use of volatile solvents in them) I use cuvets that have a screw on cap.

**It takes lots of g's to separate these two if they form together. A pretty hefty centrifuge is required to do the job properly but I've found a trick that lets me do it in even and old clinical centrifuge. After three minutes cetrifugation the 2nd phase will pack down somewhat. It's now like a wet-snow slush. If you step in that the water snow part collapses leaving the water. The same works here. Take a tip from the smaller pipetter and poke at the slush gently or smash it against the side of the tube wall. This will leave you with clear liquid which you can pipet out. In extreme cases you may have to go back into the centrifuge for another couple of minutes.

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Old 08-17-2011, 03:51 AM   #17
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*There are plastic disposable cuvets that claim decent transmission into the UV. Much less expensive, of course, but I've never tried them.
I've tried them, and was not impressed. OTOH, I have access to those $200 quartz cuvettes so it doesn't matter how not impressed I am. Great writeup, btw.
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Old 08-17-2011, 03:53 AM   #18
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Find the graduate student TAs that run the CHEM 101 labs at the local university and offer them some homebrew. I think that should get you all the chemicals you need.

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Old 08-17-2011, 03:57 AM   #19
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Find the graduate student TAs that run the CHEM 101 labs at the local university and offer them some homebrew. I think that should get you all the chemicals you need.
Right. I've got a 20-yr old boy taking chem in college starting next week. He has his instructions. The plan is coming together.

I'll buy the cuvetts and other small stuff from cynmar.com.
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Old 08-17-2011, 04:00 AM   #20
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Didn't think the book was that expensive!

What you need:
...
Wow, thanks AJ. I'll post back to this thread with results. Much, much appreciated.
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