Purification of L-tryptophan in 100 minutes Options
#1 Posted : 5/11/2020 7:47:46 AM

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This is only indirectly related to DMT, but some may still find it useful. No synthesis talk, please - the forum rules impose a limit on how far this thread can go.

Based on the following patents:
https://patentimages.sto...2ab7a8532/US5057615.pdf (English) (Russian)
https://patentimages.sto...727bbc/CN104926709A.pdf (Chinese)

You can purify L-tryptophan to >99% by recrystallizing it in aqueous acetic acid.

A minimum amount 5% to 25% solution (percent weight) of acetic acid in distilled water is used - just enough to dissolve all the L-tryptophan when the solution is hot. The weight of the glacial acetic acid in the solution should be equal or greater than the weight of L-tryptophan.

0.5% (of the L-tryptophan weight) of vitamin C or E can optionally be added to prevent oxidative degradation of the L-tryptophan in the acid. The anti-oxidant is not necessary if the acid concentration is 20% or lower.

The solution is heated with stirring to 80-95°C until complete dissolution of the L-tryptophan is observed. Any insoluble impurities are filtered out via hot filtration. The saturated solution is allowed to cool, slowly, to 30°C (room temperature) and remain at that temperature. This initial cooling period should take at least 75 minutes. The solution is then placed into a refrigerator for at least 25 more minutes to cool down to 1-5°C.

The purified L-Tryptophan is filtered out of the ice-cold solution, washed in ice-cold distilled water to remove any residual acetic acid, and dried to constant weight.

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#2 Posted : 5/11/2020 7:58:51 AM

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So, for 10g of L-tryptophan, at least 200g of 5% distilled vinegar will be required (or 10g of glacial acetic in 40g+ of distilled water) plus (optionally) 50mg of vitamin C.

The solution is heated on a magnetic hotplate with stirring to 85°C; more acidic water may be added to dissolve the L-tryptophan completely. The liquid should be fully transparent. If any insoluble impurities remain, the solution is heated up more and then quickly filtered before it cools down.

During the following 75 minutes the solution is allowed to cool down to 30°C and stay at 30°C. It is then moved to a refrigerator for 25 more minutes. Longer cooling times will result in larger and purer crystals but may increase the risk of oxidation.

Quick cold filtration under vacuum, followed by washing in cold distilled water (until the L-tryptophan no longer smells like vinegar), followed by drying, complete the process.
#3 Posted : 5/17/2020 2:52:49 PM

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Thank you . I know a very good use for this.
#4 Posted : 5/25/2020 12:40:30 PM

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Thank you!

I have struggled to recrystallize tryptophan from just water with little success (it really does not want to, even from heavily supersaturated solution).

My tryptophan has 1% taurine added and taurine is hard to remove by washing - I found no common solvents to separate the two compounds, so recrystallization was the only option.
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