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Author: Subject: Purifying luminol
mackolol
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[*] posted on 2-12-2017 at 07:04
Purifying luminol


I have water/acetone luminol solution and im wondering if it wont decompose when i distill it off to get pure luminol.
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LearnedAmateur
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[*] posted on 2-12-2017 at 08:02


According to this publication, luminol solutions are unstable toward both heat and light, so the short answer is no. Probably your best bet to let it evaporate in a cool and dark place or to crash it out of solution somehow.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4426882/

[Edited on 2-12-2017 by LearnedAmateur]




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mackolol
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[*] posted on 2-12-2017 at 08:12


Thanks a lot
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Ozone
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[*] posted on 2-12-2017 at 09:09


Luminol is quite insoluble in water at acidic pH (quite soluble in alkali as the sodium salt). If the pH is made slightly acidic, say 6, and the acetone co-solvent is evaporated under a stream of air, perhaps with a warm water bath (better, N2 -- nitrogen blow-down technique), the luminol should crash out.

https://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4426882/

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happyfooddance
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[*] posted on 2-12-2017 at 12:26


Ozone: you are so bad-ass. I have always appreciated your contributions, and it makes me really happy to see members like you sticking around and helping out.
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mackolol
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[*] posted on 4-12-2017 at 09:36


Will it be OK if i use spirit vinegar (food acetic acid)? Because i dont want to use solid acid because it will contaminate my luminol. And will it work if i just simply put stream of air bubbling through solution? Wont it decompose luminol by oxidation or something?

[Edited on 4-12-2017 by mackolol]
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Ozone
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[*] posted on 4-12-2017 at 18:57


The way I see it, the acid doesn't matter that much -- it will remain in the mother liquor. Evaporation via stream of gas facilitates evaporation of the quite volatile acetone--this cools the solution helping to avoid oxidation. Using nitrogen, or a better, a blanketing gas like argon, will also mitigate this. It shouldn't take too long (depending on your acetone content--which wasn't given), just minimize photochemical reactions -- it seems to have absorbance maxima at 300 and 350 nm (UV cutoff around 250nm), and nothing much at > 400, so avoiding UV and blue light would be best.

Honestly, though, we isolated the stuff in a flask, under air, in a no-frills lab space with fluorescent lighting and yields were OK...so work as fast as you can whilst working safely.

Question: will adding further water crash it out? Will adding acidified water crash out more? You should try this at very small scale in a test tube, or something.

Best of luck to you,

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