A word about nicotine purity/storage

[DVap]

Much is made of trying to find the optimal storage conditions for nicotine concentrates to be diluted into working eliquids. Similarly, much is also made of finding concentrates with good pure nicotine.

These are good things, but ultimately, I wonder how much they really matter.

Consider this image from Exogenesis. This is from his vapor trapping experiments where he set up an apparatus to auto-vape e-liquid and electrostatically condense the vapor for nicotine determination:





On the left, you see eliquid made from pharma grade nicotine. On the right you see the same liquid after it's been atomized and condensed.

No matter how well we source and store the stuff, the stuff on right is what we're vaping, not the stuff on the left. After all, the last thing we do before we inhale our precious liquid is heat it up aggressively in a stream of air containing about 20% oxygen.

I'm not out to make a big deal about this inescapable fact of vaping, but it's at least something to consider when we might be tempted to worry excessively about our concentrates getting a slight yellow/brown tinge.

[Nikhil]

A nice and informative summary there. Also interesting is that the nicotine content of the re-condensed tinted liquid always contained >90% of the original nicotine of the clear liquid before vaporization. Basically, very little is destroyed before it goes into your lungs.

[Kurt]

Its my understanding that the yellow is from cotamine, which can color a solution with VERY little cotamine. Cotamine itself is not inactive, just not as active as nic. It is the primary reaction product of nicotine and O2. O2 is present in VG and PG, but its solubility is quite low. None the less there is trace O2 present, and with time it will react with nic. However, even if it ALL reacts, it is a very small amount, and as I said, cot is still somewhat active. So a little discoloration is fine. Maybe even a lot of discoloration.

None the less, as a chemist myself, I like to think I can control reactions. In my storage method, I use small bottles for unflavored high-nic liquid, have very little head room above the liquid, and freeze them. This will certainly slow any nic-to-cot reactions, and also any biological growth, however unlikely that would be in VG or PG. Call it overkill for added peace of mind. I am actually more concerned about the biological with VG, which is all I use, than loss of nic potency. Loss of nic just means I will vape a little more. Bugs growing means I will be sick and tossing a lot of juice out.

The 100 mg MFS VG unflavored I am currently using, as in an open bottle that I've been keeping at room temp for making my DIYs, has now after 4 months turned yellow. Not deeply so, but it is similar in shade to the pic shown here. And it is, as far as I can tell without titration, every bit as potent as it was in January when I bought it.

Great discussion, and really great experimental investigations. We are all blessed to have such excellent scientists working with their own resources here.

[DVap]

Its my understanding that the yellow is from cotamine, which can color a solution with VERY little cotamine. Cotamine itself is not inactive, just not as active as nic. It is the primary reaction product of nicotine and O2. O2 is present in VG and PG, but its solubility is quite low. None the less there is trace O2 present, and with time it will react with nic. However, even if it ALL reacts, it is a very small amount, and as I said, cot is still somewhat active. So a little discoloration is fine. Maybe even a lot of discoloration.

None the less, as a chemist myself, I like to think I can control reactions. In my storage method, I use small bottles for unflavored high-nic liquid, have very little head room above the liquid, and freeze them. This will certainly slow any nic-to-cot reactions, and also any biological growth, however unlikely that would be in VG or PG. Call it overkill for added peace of mind. I am actually more concerned about the biological with VG, which is all I use, than loss of nic potency. Loss of nic just means I will vape a little more. Bugs growing means I will be sick and tossing a lot of juice out.

The 100 mg MFS VG unflavored I am currently using, as in an open bottle that I've been keeping at room temp for making my DIYs, has now after 4 months turned yellow. Not deeply so, but it is similar in shade to the pic shown here. And it is, as far as I can tell without titration, every bit as potent as it was in January when I bought it.

Great discussion, and really great experimental investigations. We are all blessed to have such excellent scientists working with their own resources here.

Dr. Kurt, you sure you're not thinking of cotinine?

[exogenesis]

Interesting thoughts, & true, still, better quality stuff in, probably = better quality stuff out.

Couple of gotchas about that experiment-set, the 'nicotine' measured was actually
'wet-titratable nitrogen equivalent to nicotine',
so in fact it could have been all cotinine or nicotine-oxide or something else for all I know
(doubt it though).

The colour seen develops (to various degrees, depending on current / flow-rate),
even with zero-nic. PG or glycerol when vaporised & re-condensed (caramelisation?)


In reality the experiment was pretty crude, don't have the proper gear to say
'this is what chemically alters when you vape e-juice'.

Still the indications were 'good'

[Kurt]

Dr. Kurt, you sure you're not thinking of cotinine?

Doh! Yes, I meant cotinine...the lactam. For some reason I always make that mistake. Thanks for the correction.

[Kurt]

Interesting thoughts, & true, still, better quality stuff in, probably = better quality stuff out.

Couple of gotchas about that experiment-set, the 'nicotine' measured was actually
'wet-titratable nitrogen equivalent to nicotine',
so in fact it could have been all cotinine or nicotine-oxide or something else for all I know
(doubt it though).

The colour seen develops (to various degrees, depending on current / flow-rate),
even with zero-nic. PG or glycerol when vaporised & re-condensed (caramelisation?)


In reality the experiment was pretty crude, don't have the proper gear to say
'this is what chemically alters when you vape e-juice'.

Still the indications were 'good'

Exo, the 0-nic results are interesting, and do point to possible caramelization of PG or VG. Also, and this is something DVap and I discussed a while back, still without a clear answer, is that cotinine is a lactam, and thus the nitrogen is not nearly as basic as the amine N in nicotine. The equivalence point should be the same for equal equivalents of those two, but the pH curve should be different. And the 1/2-eq point, pKa of the conjugate acid, should be at different pHs for the two. Its a weak vs really weak base thing. pKb of nic should be around 5 (pKa around 9). pKb of cot should be maybe 7-9, pKa around 4-7.

I wonder if there is a way to completely turn nic to cot...maybe bubble O2 through overnight? Then use that as a standard for cot. Just a thought. How a mix of those two would show up in a pH curve, I don't know, but it seems it should be solvable with some algebra. And of course there is the pyridine, and whatever added effect it has (probably small in comparison, as it is the weakest base)

[exogenesis]

You're absolutely right Kurt, there's a massive difference in the titration curve
between nicotine & cotinine, so much so that it'd be easy to tell the difference.

I must be getting rusty, glad you picked that up

In fact the simple wet-titration method won't show the titration point of cotinine
(or nic.oxide) due to getting mixed up with the excess-acid part of the slope,
it'll 'soak up' the added acid but there's no quantification point visible,
or at least difficult to evaluate anything like accurately.

'Best' pKa values I know are nicotine 8.02 and cotinine 4.88 (same for nic. oxide) from :
http://www.unitedchem.com/sitefiles/...0Alkaloids.pdf



(second pKa for both nicotine & cotinine is 3.12)

So titration curves would look like (courtesy of CutTiPot sim.):

[Kurt]

Exo, this is exactly as I thought. Nice work! The eq pt for cot is almost without inflection, but by taking many points and getting the local derivatives at each point, the inflection should be clear, both for 1/2-eq pt and eq pt. Spectroscopy would of course be useful in measuring the amount of cot present, if the molar extinction coefficient is known. I doubt anyone has a spectrometer laying around in the basement though.


It is my understanding that cot is the primary reaction product of nic with ambient O2, but the other nic-derivatives are generated in a combustion reaction from smoking. Am I correct on this?

great and important thread!

[exogenesis]

Late reply due to enforced absence cos of damaged phone lines,

I think nicotine oxide is the first reactant, when it involves just air (&/or heat).

Think cotinine is pretty much an enzyme-action product (as well as the oxide)



Both are 'yellowish'.


Not quite sure what DVap was highlighting in this thread, obviously vaping causes some
nicotine 'oxidation' & breakdown, but the tests done showed good recovery, thinking they show even
better results after this discussion Kurt

- i.e. more definite nicotine-indicating titrations-curves than I thought, rather than oxidation reactants.