Why nicotine salts?
I can't find much information on nic salts, but I did find an interesting reddit post. This was a long post so this is only a portion.
"If you hadn't heard, Pax claims the Juul is more effective for smokers than normal vapes because they use 'natural nicotine salts,' as found in the tobacco leaf instead of the freebase nicotine used in normal e-liquids & other pre-filled cigalikes. They show
this chart, of nicotine blood plasma levels vs. time, to demonstrate the differences (but don't cite a proper study or published research protocol). It certainly appears compelling, and I've heard people describe Juul as delivering the 'rush' the remember from cigarettes (though that could just be the 50+ mg/mL nic level in the pods!). However, at least based on my knowledge, that just doesn't jive with the science. So what's the deal here?
Nicotine appears in nature in the tobacco plant (and other plants) in salt form -- a positively-charged ionized nicotine molecule bound to negatively-charged organic acid conjugates like ascorbate, citrate, or benzoate. When nicotine is extracted from plant matter to make pure nicotine concentrate, ammonia is used to increase the pH & revert the nicotine to its neutrally-charged free base form.
This is done for two reasons:
1) 'Freebase' nicotine is
much more effectively absorbed in vapor form. Nicotine salts are more stable but harder to vaporize, as they require a higher temperature to volatilize than the freebase. In fact, adding ammonia-forming compounds to cigarettes so that ammonia is released under combustion and it reacts with the nicotine salts in the tobacco to volatilize the nicotine, increasing the conversion of (mostly-inactive) particulate nicotine into gas-phase nicotine 100-fold in
this study. This form of nicotine also crosses the blood-brain barrier much more easily due to its neutral charge, thereby improving delivery of nicotine to the neurons upon which it exerts its primary effect.
2) The
process of extracting nicotine from plant matter uses this acid-base reaction to solubilize the nicotine for extraction by butane (or other non-polar solvents). Converting back to the salt form appears to be seen as pointless and counterproductive, based on [1] above.
Furthermore, the Juul doesn't actually seem to include those 'natural nicotine salts' as they occur in tobacco. From the (sparse) information they've posted publicly, it seems that the JuulPods actually include the same freebase nicotine we're all familiar with from our own DIY escapades. However, Pax has added benzoic acid to their e-liquid, under the premise that the presence of H+ ions would ionize the nicotine, resulting in the formation of nicotine benzoate salt during the heat of vaporization.
In other words, it seems like Pax is using a process that's almost exactly the inverse of the ammonia-forming compounds used in cigarettes, which also use heat to catalyze a similar acid-base reaction in the
opposite direction, from salt TO freebase.
If you want to read more about the use of ammonia-freebase conversion in cigarettes to purportedly increase the addictiveness (aka improve the 'flavor', according to Big Tobacco),
this paper tells the whole story in glorious detail.
So, to break down my question into the simplest terms, given the available evidence seems to directly contradict the statements from Pax about the differential efficacy of nicotine salts and freebase in vapor/smoke, why would they attempt to convert their nicotine freebase
back into the salt form? And furthermore, what is the explanation for their chart, which was supposedly produced using data from a study funded by Pax, but conducted independently. Is there an alternative explanation that would reconcile the apparent opposition between the chart and the extant literature about nicotine acid/base reactions?"
The linked study
http://pubs.acs.org/doi/abs/10.1021/es970402f
The paper
The SECRET and SOUL of Marlboro: Phillip Morris and the Origins, Spread, and Denial of Nicotine Freebasing
Nicotine Freebase vs. Salt: Absorption & Vaporization Efficacy, contrasted with Pax Juul claims about Benzoic Acid & 'natural tobacco nicotine salts' -- WTFbroscience?! • /r/Deeper_DIY
