Any interest in determining nicotine--by DVAP

[DVap]

ps: given the low flash point, although seemingly unlikely i wonder if the nic vapor is actually combusting rather than just fast oxidising once in the gas phase?

Kin, you need to take into account that flashpoint is a property that is calculated in air. With nicotine in e-liquid, it enters the vapor phase along with a great deal more PG and or VG than the nicotine. The nicotine is thus effectively fairly-well shielded from the oxidizer (air).

pps: the percentage loss at around 50% is intriguing in it's own right - why not just a small part or nearly all of it? Why half is affected differently to the other half? Might be just a boring coinicidence resulting from timescale for example; but curious nonetheless.

This one really has my attention, and so far, I don't know the answer. Much of my though in attempting to come up with a closed-end trap comes from the uncertainty of operating a flow-through trap (the liquid-argon trap). This uncertainty is sufficient for the critic in me to question any of a number of possible defects in such a system. An additional bit of thought comes from the fact that the argon trap is bulky, hard to operate, and requires me to consume materials that, while trivial in amount, I shouldn't be consuming all the same. The closed trap with vacuum as the vaping impetus is clearly the way to proceed.

[DVap]

Would be interested to know what they mean by 'organic acid', citric & acetic are organic acids afaik.

Organic acids vs mineral acids.

The strongest of acids are mineral acids like HCl, H2SO4, HNO3. When an acid is referred to as a "strong acid", it has nothing to do with how nasty the acid is if you get some of it on you. It refers to the degree of dissociation of the acid in solution into protons (Hydrogen ions) and the corresponding negative anion. Strong acids dissociate 100%.

Organic acids are acidic because they too can liberate protons (hydrogen ions) in solution. Organic acids are weak acids because they don't dissociate anywhere near fully into hydrogen ions and negative anions in solution. The thing that makes for the classic organic acid, or a carboxylic acid is the OH functionality adjacent to a C=O functionality (a carbonyl group). This is sometimes simplistically written as COOH. Though O=C-O-H is far more accurate.

We need to look at what is meant, in practical terms, by a "weak" acid.

Acetic acid, CH3-COOH, is a weak acid. If we make a 1N solution of HCl, the pH will be 0, if we make a 1N solution of acetic acid, the pH will be 2.4. This is incredibly less acidic. Why? Because the the dissociation constant between acetic acid and proton + acetate anion is relatively high. The 2.4 pH tells us that less than a half percent of the acetic acid molecules present are dissociated... and any hydrogen that isn't dissociated, doesn't act as an acid. 1N acetic acid is of a strength we generally associate with vinegar.

Looking at it another way, if an e-liquid contains 1% acetic acid, it contains 10 mg/mL acetic acid. How might this mess with a nicotine determination? Assuming a 0.4% dissociation, the proton concentration as a result of the acid will be ~ 10 mg/mL * 0.4%, or 0.04 mg/mL. The problem is, the relatively low dissociation still makes hydrogen ions, and these still neutralize nicotine. As the nicotine pulls the hydrogen ions out of solution, the equilbrium is shifted and more acetic acid dissociates. In the end, acetic acid will neutralize nicotine as well as any strong acid.

What am I suggesting?

Acetic Acid is rather good with fish and chips, but I don't want it in my e-liquid.

Citric acid, while not so good with fish and chips, is fine in fruit, but keep it out of my e-liquid.

[kinabaloo]

Kin, you need to take into account that flashpoint is a property that is calculated in air. With nicotine in e-liquid, it enters the vapor phase along with a great deal more PG and or VG than the nicotine. The nicotine is thus effectively fairly-well shielded from the oxidizer (air).

This one really has my attention, and so far, I don't know the answer. Much of my though in attempting to come up with a closed-end trap comes from the uncertainty of operating a flow-through trap (the liquid-argon trap). This uncertainty is sufficient for the critic in me to question any of a number of possible defects in such a system. An additional bit of thought comes from the fact that the argon trap is bulky, hard to operate, and requires me to consume materials that, while trivial in amount, I shouldn't be consuming all the same. The closed trap with vacuum as the vaping impetus is clearly the way to proceed.

Indeed, that's why it is a quirky explanation, but one that could explain the result. Not suggesting that any flame would be seen if looked into the atty; rather tens of very brief micro flashes. Combustion is one example of the sort of chain-reaction that might be involved (perhaps needs to be, to account for the high loss), in this case, energy release maintaining the temp needed).

If it should turn out that vaping in an inert atmosphere also sees the nic loss. we should perhaps consider nic in ethanol, and in water, as alternative bases to see if the result is (more or less) the same.

Perhaps without the shielding of PG vapor, (nearly) all the nic would be lost. I mentioned before this effect in terms of the nic getting quickly redissolced in recondensed PG, but there is a shielding involved in the gas phase too, as you say. If this is significant (as seems likely, unless there is some reaction between the nic and the glycol) then higher % nic liquids would be expected to suffer greater loss (i.e. testable, though not sufficient as proof of exactly what is happening; if the %nic makes no difference, hmmm).

Fractional distillation may play a part too, with nic having about the highest BP. The heating is far from a simple affair; although generally the coil has an inner wick to buffer the temp (increased heat capacity), much of the vaporised liquid arrives at the coil as droplets onto various sites of the already heated coil; it is not a uniform situation. Both nic and VG are very eluctant to evaporate and there is a chance for super-heating to occur (leading to decomposition); this alone could not account for the high loss, without there being some reactive species involved amplifying the effect.

ps: the feed of a reaction in equilibrium where reactants are pulled out of the equation somehow (most easily seen in terms of concentrations as in the discussion of effects of a weakly dissociated acid; DVap, above) is another mechanism that might be involved, though possibly the time-scale is too short?

DVap - the closed trap arrangement is a good advance in the experimental design; might be a bit tricky (though no more so than using liquid argon) but should be lossless, yes.

[exogenesis]

.....

What am I suggesting?
Acetic Acid is rather good with fish and chips, but I don't want it in my e-liquid.

Citric acid, while not so good with fish and chips, is fine in fruit, but keep it out of my e-liquid.

very true.

Presumably where these organic acids occur in juices, they are put in as
'acidity regulators' and/or preservatives/antimicrobial agents,
to me this seems a little bit of an unecessary cross-over from food stabilisation.

The Wikipedia juice recipes table presumably has generalised 'organic' acids,
to mean acetic & citric acids alone or in combination.
I would hope they don't mean imply any of the other ones, some of
which are used in foods (e.g. lactic).

[kinabaloo]

At least acetic acid (aka ethanoic acid) is vapable (BP ~115C) whereas citric acid will decompose on the coil (~175C) producing carbon monoxide.

[DVap]

Good points gentlemen.

If we are looking a flash, or even limited "burst" flash, we're still looking at oxidation being the root culprit.

As for acids, when analog smoke is acidic, an analog loses the ability to provide a strong "rush". The protonated nicotine is absorbed more slowly via particles left in the mouth and throat and slowly absorbed or simply swallowed.

The same would hold true for vaping, assuming that nicotine salts make it into the vapor... something I'm not yet prepared to assume they do or don't.

The two extreme possibilities are:

nicotine salts make it into the vapor: They get absorbed eventually, and might not do any harm to the overall dosing.

nicotine salts don't make it into the vapor at all: They get plated out on the atty and oxidized to gunk or build up in the cart. In this case, they have no place at all in e-liquids, unless one a) wants them there for a particular reason, and b) doesn't mind that they react with nicotine.

[DVap]

Here's an article that I consider a "must-read". I believe it asks and answers the right questions, including some I'd not considered about pH and nicotine.

[exogenesis]

If I'm reading that right the bullet points are:

1 nicotine is vapourised equally well regardless of free-base or (organic) salt-form, between 100 & 220 'C
- but still the free-base form vapourises at the lower temperature.

2 contrary to popular belief, added ammonia in ciggie processing is all
about the binding process
during 'reconstituted tobacco' production, rather than to have 'more free-base' nicotine.

3 smoke 'pH' is not equivalent to aqueous nicotine pH
Certainly challenges some of our assumptions.

"pH of cigarette smoke is 'acid' (adsorbs in lung only)"
"pH of pipe smoke is 'alkaline' (adorbs in mouth/nasal cavity)"
These statements may have a different emphasis if the article is fully correct.

Very good find DVap

[DVap]

If I'm reading that right the bullet points are:

1 nicotine is vapourised equally well regardless of free-base or (organic) salt-form, between 100 & 220 'C
- but still the free-base form vapourises at the lower temperature.

2 contrary to popular belief, added ammonia in ciggie processing is all
about the binding process
during 'reconstituted tobacco' production, rather than to have 'more free-base' nicotine.

3 smoke 'pH' is not equivalent to aqueous nicotine pH
Certainly challenges some of our assumptions.

"pH of cigarette smoke is 'acid' (adsorbs in lung only)"
"pH of pipe smoke is 'alkaline' (adorbs in mouth/nasal cavity)"
These statements may have a different emphasis if the article is fully correct.

Very good find DVap

Not to mention the finding that nicotine carboxylic acids can be deprotonated by heating and yield up the free base.


Though the article refers the combustion of analogs, the same is likely true with e-liquid vaporization. The upshot appears to be that the system is too complex to apply first-glance principles with expected results. The system though, seems to be more agreeable to the free base than the first-glance principles might suggest.

The useful investigation might end up being, as I've suspected, less about understanding the nicotine discrepancy, and more about getting it quantified. At this point, I can envision the dry nitrogen vape test to test for oxidation as a contributor to the discrepancy. Also I can envision a vape test of nicotine neutralized with acetic acid to determine if we end up with free nicotine in the vapor, despite the acid. Actually, I can't stop envisioning new tests.. so I'd best go watch some TV now.

[exogenesis]

Juice with added acid, but still gets free-base in the vapour....
yes that certainly would be good to quantify.

To the Bat Cave !