I did an STB with an acid pre-soak.
mhrb fine powder in phosphoric acid solution in 2L erlenmayer flask for 6h on magnetic stirrer (PTFE coated stirrer bar 3cm), followed by basification with 100g NaOH for 6h in the same erlenmayer on the same magnetic stirrer.

Erlenmayer flask is Schott Duran 3.3
After finishing the extraction and disposing the black basified solution I observed on the bottom of this flask a circle with 3cm in diameter where the glass is scratched uniformly.
I mean not only 2 or 3 lines but the entire surface of this circle is scratched.
It could be only from the stirrer bar.

I didn't think that the stirrer bar could to this if used in a solution with fine powered mimosa.
Only the fine powder that was moved by the stirrer bar could have done this.


Had anybody else the same thing happened?
Is the extracted DMT contaminated with glass?
Should I use in the future this flask?

Flasks do get scuffed up from normal use. NaOH has a tendency to exacerbate this. You could try cleaning with vinegar and rinse with acetone/alcohol make sure what you are cleaning with good contact on the area.

Your flask is fine for future use more than likely. Make sure they are not cracks and are indeed only scratches . Sillicates are insoluble in nonpolar solvents so your dmt should be safe from the milligram that may be missing.

Where you heating this flask simultaneously(such as a hot-plate)?

I cleaned it up thoroughly (vinegar, soap, warm NaOCl) so those are real scratches on the glass.
It wasn't heated in the same time on the stirrer (it's a DIY stirrer).

Well I would say this is normal wear and tear. The majority of flasks I have have stirrer marks. I'm not sure if it's from PTFE scoring/rubbing into the glass or if it's from the stirrer whipping NaOH and eating a super minute amount of the glass. You're fine.

If you're real worried about it you know add NaOH slowly next time, but borosilicate glass is made for this.