Purification of drugs via AB extraction

[doorknob]

OK, so I'm trying to purify my 2g amphetamine paste with an ab extraction, NaOH as the strong basing agent and hexane as my non polar solvent. Added NaOH until pH 11.5. Saw a layer of freebase develop so should have got a good yeild. First time I got pretty much nothing, don't think I waited long enough or shook it up enough. Second time when salting I got a bit, about 80mg.

I checked the pH of the hexane when it was sat on the water mix, still 7 (what should it be? is that right or should it be 11-12?). So I added 20ml IPA for some reason and shook at all up. This time when salting I got a good yeild, nearly a gram of amphetamine sulphate powder/adulterant. Now, because NaOH is soluble in IPA slightly (about 50mg/ml i've heard?), I guess some passed over to the NP layer. It doesn't taste particularly caustic but I don't really want to snort it if it contains it obviously.

Is hexane even a good solvent to use? I didn't even really think about it, just presumed it'd be good, checked a pharmaceutical chemistry (really, not just a recipe of the internet) amphetamine manual that instructed to use hexane after basing.

The first time, the 20% H2SO4/80%IPA mix just sank to the bottom and I couldn't get it to mix properly. Should I add IPA to my final hexane pull before salting?

Anyway I can separate the impurities without a second AB extraction? If I dissolved it in water, made sure pH was definitely 7 with either acid or baking soda then evaporated, would it be safe to consume anyway? I'm guessing there could be sodium sulphate in there which should be harmless right?

Will any NaOH have even passed over? Would the IPA I added to the complete mix even pass over or stay in the water layer?

Thanks!

 

[pasha]

Purification threads belong in Advanced Drug Discussion.

Basic Drug Discussion -> Advanced Drug Discussion

 

[doorknob]

Purification threads belong in Advanced Drug Discussion.

Basic Drug Discussion -> Advanced Drug Discussion

Ah sorry, thought it was a basic question but thanks

 

[sekio]

I checked the pH of the hexane when it was sat on the water mix, still 7 (what should it be? is that right or should it be 11-12?)

pH = hydrogen ion activity in water. In hexane, there's nothing to carry hydrogen ions, so there's no pH to really measure.

Now, because NaOH is soluble in IPA slightly (about 50mg/ml i've heard?), I guess some passed over to the NP layer.

Salts in general will only dissolve in a nonpolar solvent if there's nowhere left for them to go; in this case the NAOH would have preferred to stay in the water layer.

The first time, the 20% H2SO4/80%IPA mix just sank to the bottom and I couldn't get it to mix properly. Should I add IPA to my final hexane pull before salting?

No, you're doing *something* wrong.

1. Dissolve amphetmine paste in cold water.
2. Add NaOH with vigorous stirring. Let stir for maybe 10 mins. (Mixture warms up, be careful) Measure pH of the aqueous layer to be at e.g. pH 12+
3. Add hexane with VIGOROUS stirring. Better still, load the whole mess in a seperatory funnel and give it a really strong shake.
4. Seperate off the hexane, put it aside
5. Repeat 2 more extractions with hexane. Per Vogel's advice, 3 x 50ml extractions are better and more efficient than 1x 150ml extraction.
6. Take your hexane and give it a quick shake over 50-100ml of saturated brine (This will remove any left over salts, they will prefer to be in the brine layer).
7. (optional) add anhydrous magnesium sulphate and stir for 30 min to dry hexane solution. filter to remove the drying agent
8. gas with HCl

You don't at any point need to use isopropanol. Amphetamine base has fine solubility in hexane. If you don't extract anything with this procedure, it's likely what you have is not amphetamine.

 

[doorknob]

pH = hydrogen ion activity in water. In hexane, there's nothing to carry hydrogen ions, so there's no pH to really measure.



Salts in general will only dissolve in a nonpolar solvent if there's nowhere left for them to go; in this case the NAOH would have preferred to stay in the water layer.



No, you're doing *something* wrong.

1. Dissolve amphetmine paste in cold water.
2. Add NaOH with vigorous stirring. Let stir for maybe 10 mins. (Mixture warms up, be careful) Measure pH of the aqueous layer to be at e.g. pH 12+
3. Add hexane with VIGOROUS stirring. Better still, load the whole mess in a seperatory funnel and give it a really strong shake.
4. Seperate off the hexane, put it aside
5. Repeat 2 more extractions with hexane. Per Vogel's advice, 3 x 50ml extractions are better and more efficient than 1x 150ml extraction.
6. Take your hexane and give it a quick shake over 50-100ml of saturated brine (This will remove any left over salts, they will prefer to be in the brine layer).
7. (optional) add anhydrous magnesium sulphate and stir for 30 min to dry hexane solution. filter to remove the drying agent
8. gas with HCl

You don't at any point need to use isopropanol. Amphetamine base has fine solubility in hexane. If you don't extract anything with this procedure, it's likely what you have is not amphetamine.

Many thanks,

I don't think I shook it hard enough the first time, but spent a good while the second netting about 850mg amp sulphate. I did 3x20ml hexane pulls, 50 ml be better?

I thought the HCl salt was unstable/hygroscopic? Would gassing with HCL be a better option?

The reason I used IPA was to dilute my 98% sulphuric acid, I think IPA dissolves in hexane so I figures it'd mix better. Plus amp sulphate isn't soluble in it either so I could just filter crystals.

I understand what pH is yes to the extend that it was h ion concentration, but not just in water so never knew hexane wouldn't give a pH, so how do you measure pH when adding h2so4? i could calculate the amount needed but that could be difficult when purity is unknown. Just add until no more salt appears? Would it be better to dilute my acid with water then measure the pH of the water layer after shaking to ensure all base has reacted then evap water?

Thanks!

 

[sekio]

evaporating water from amp sulphate will be hard. you are indeed correct that the hcl salt is hygroscopic, too.

3x20 ml is more than enough. it sounds like you just needed to mix more vigorously.

so how do you measure pH when adding h2so4?

you add a few drops of the mixture to 1ml of water and test the ph of that.

 

[doorknob]

evaporating water from amp sulphate will be hard. you are indeed correct that the hcl salt is hygroscopic, too.

3x20 ml is more than enough. it sounds like you just needed to mix more vigorously.



you add a few drops of the mixture to 1ml of water and test the ph of that.

Many thanks indeed my friend, that is absolutely brilliant!

Snorted a bit anyway, 30mg had me away nicely so it was a success eventually but with my new knowledge it should be even better next time though unlikely I'll come across any paste that's stronger anyway, it's always good to purify. Plus it doesn't smell of cat piss.


How's about... heating slowly to speed up evaporation the water/amp mix after separating from hexane until crystals start to form, then dumping acetone in to crash out the crystals? Or would I still have some dissolved in the water? Hmm.

Anyway cheers, you've been a brilliant help, thanks a lot buddy

 

[Megalum]

Perhaps you could change it to a hcl salt, then do the basic acetone wash... If you need freebase you could always base it back after. You will get a better yield, In my opinion.