Making pure paracetamol by mixing with ethanol

Athiril · Aug 18, 2011

Gerald C Koch said:
Very curious. The tablets appear stable but once extracted the acetaminophen turns brown. I have some tablets that are at least 5 years old and show no discoloration. I will have to try this out.

I quoted the stability of the water solution since such solutions are more susceptable to oxidation than the solid would be.

It doesn't turn brown instantly. It happens over a number of days. Hence unstable for any kind of storage. You can see it happen quicker if you leave it out on a piece of paper, come back the next day and prepare some fresh extract.

Alcohol solutions will also turn pink on heating.

The filler contains preservatives.
http://formulation.vinensia.com/2010/08/paracetamolacetaminophen-tablet.html

More info
http://www.ncbi.nlm.nih.gov/pubmed/16414737

More again
http://pubs.rsc.org/en/Content/ArticleLanding/2010/CC/b927429d

Some technical info on hydrolysis of paracetamol
http://books.google.com.au/books?id...3#v=onepage&q=acetaminophen stability&f=false

daveandiputra · Aug 18, 2011

Hi all, thanks for all the inputs. The reason I still can't make the Parodinal is altough I can measure the paracetamol with liquid but I still need scales for the other chemicals

And regarding the form and color of the crystals until this day ( more than a week from when I first scrape it after the ethanol is fully evaporated) is still the same. So don't know if that means it is still usable. But as arthiril claims first hand experience on the keeping properties, i'll just make another batch when I get a new scale.

Gerald C Koch · Aug 18, 2011

Athiril,

The two preservatives listed for the tablet formulation (methyl paraben and propyl paraben) on the one link are to prevent mold from growing on the tablets. They are not to preserve the acetaminophen.

Yes, this compound will hydrolyse when in strongly acidic or alkaline aqueous solutions. This should not occur in alcohol solution.

Heat, light, and exposure to oxygen can cause some degradation. But nothing on the supplied links suggests anything like a matter of a day or so.

I have extracted the acetominaphen from 2 500 mg tablets with methyl alcohol and will report on any chenges that may occur.

Jerry

Athiril · Aug 19, 2011

Gerald C Koch said:
Athiril,

The two preservatives listed for the tablet formulation (methyl paraben and propyl paraben) on the one link are to prevent mold from growing on the tablets. They are not to preserve the acetaminophen.

Yes, this compound will hydrolyse when in strongly acidic or alkaline aqueous solutions. This should not occur in alcohol solution.

Heat, light, and exposure to oxygen can cause some degradation. But nothing on the supplied links suggests anything like a matter of a day or so.

I have extracted the acetominaphen from 2 500 mg tablets with methyl alcohol and will report on any chenges that may occur.

Jerry

Maybe we have different forms between countries between the cheapest brands, I also used denatured alcohol, though I don't think that should affect it.

I ground my extract into a fine powder with a mortar and pestle as well.

Next week when I am not dirt poor, I'll get some supplies make an extract. And take before and after photos.

Athiril · Aug 19, 2011

daveandiputra said:
Hi all, thanks for all the inputs. The reason I still can't make the Parodinal is altough I can measure the paracetamol with liquid but I still need scales for the other chemicals

And regarding the form and color of the crystals until this day ( more than a week from when I first scrape it after the ethanol is fully evaporated) is still the same. So don't know if that means it is still usable. But as arthiril claims first hand experience on the keeping properties, i'll just make another batch when I get a new scale.

If it hasn't darkened it'd be okay.

Gerald C Koch · Aug 20, 2011

After 2 days the extracted acetominaphen is still white, no discoloration. Will report again after 1 week.

daveandiputra · Aug 23, 2011

this is my first try result about three weeks old (and a correction what i thought to be ethanol was actually methanol)

Murray Kelly · Aug 24, 2011

Looking good, Dave!

Athiril · Aug 24, 2011

daveandiputra said:
this is my first try result about three weeks old (and a correction what i thought to be ethanol was actually methanol)

Looks fine for usage.

daveandiputra · Aug 25, 2011

Gerald C Koch said:
After 2 days the extracted acetominaphen is still white, no discoloration. Will report again after 1 week.

please share the result Jerry

Murray Kelly said:
Looking good, Dave!

HI Murray thanks.

Athiril said:
Looks fine for usage.

as soon as i get a new scale, i'll mix a small batch to test

Gerald C Koch · Aug 25, 2011

After 1 week still no discoloration. The solutution was evaporated in a white porcelain dish so any discoloration would be immediately seen. The crystals were also left exposed to the air.

Jerry

karthik · Aug 30, 2011

What would happen if you added water to a saturated solution of paracetamol in 90% alcohol? I was wondering if the lower solubility of paracetamol in water would cause it to precipitate out, or if it still stays associated to the alcohol molecules and hence stays in solution.

(My guess: If adding water is equivalent to starting with (a larger volume of) 50% alcohol instead of 90%, and if the decreased solubility of paracetamol in 50% alcohol exactly gets compensated for by the increased volume, then I guess there wouldn't be any precipitate.)

Athiril · Sep 4, 2011

karthik, I just finished grinding 336 tablets in a large mortar and pestle. I've been wondering that myself. It's something I shall try. I was also wondering if esterification would do it (such as with acetic acid).

Gerald C Koch · Sep 4, 2011

After 2 weeks still no discoloration.

Athiril · Sep 4, 2011

I put a few drops into 250mL of cold water... haven't seen anything precipitate out, am leaving it sit there.

Making pure paracetamol by mixing with ethanol

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