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mikepetro

Effects of Heat on Nicotine Degradation

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by , 05-05-2014 at 04:08 PM (609 Views)
I want to determine the best bath temperature for speed steeping ejuice via a hot water bath. I want to know the effects of heat on Nicotine concentration, i.e. am I sacrificing potency, and if so how much.

Here is the Test Protocol I am using.

  • Make a large batch of 50/50 PG/VG with ~4% nic, no flavoring or other dilutants.
  • Fill four 1oz Boston Rounds with this mixture.
  • Mark one bottle as the "Control Sample" and set it aside.
  • Mark each of the other 3 bottles with 125F, 150F, and 175F.
  • Put each bottle in a hot water bath (crock pot) for 8 hours at the specified temp.
  • When all batches are complete pull three 5ml samples from each of the four bottles and titrate them, using the average of the 3 titrations as the test result. If any given test result is more than 10% different than the other two, throw it out and redo it as it was probably inaccurate.


To test the nicotine levels I use the following protocol.

  • Rinse Erlenmeyer flask, and syringes, with distilled water
  • Using a syringe measure exactly 5ml of sample into the flask
  • Add ~20ml distilled water (precision not required because water has a neutral ph)
  • Add 3 drops of bromothymol blue pH indicator per ml of sample (more if nic levels are expected to be high) and swirl to mix. In this case 15 drops.
  • Using a 10ml Class A Burette, dispense a slow stream of 0.1N reagent grade hydrochloric acid into flask (swirling flask continuously) until color starts to change to green.
  • Slow stream of 0.1 N HCL down to a drop and continue adding until color changes to yellow, swirling flask after each drop.
  • Note how much HCL was consumed
  • Multiply HCL consumed by 16.223
  • Divide result above by the sample size, in this case 5

Accuracy is affected by sample size, reagent concentration, visual cues of color, visual judgement of syringe level, and technique. I use a larger sample size, and a weaker reagent, for higher accuracy. I estimate my accuracy at +/- 2% or better, hence the reason for testing 3 samples and averaging them, further reducing the margin of error.

Test results are in:

Control Sample: 36.01 mg/l
125F Sample: 35.69 mg/l
150F Sample:
33.09 mg/l
175F Sample:
32.12 mg/l


So it was clear, heat degrades the nicotine. The effect wasnt too bad at 125F, but at 150F there was an 8% loss, and at 175F there was a 10% loss.

This isnt the whole story though, take a look at the conversation I had with a chemist. The layman's version is that the heat can turn nicotine alkaloids into different alkaloids, ones that would still test positive as nicotine in a titration test but might not have the same stimulant effect on the human body.

One issue you might wish to keep in mind is that nicotine oxidation, while it results in a net loss of nicotine, does not result in a net loss of alkaloid content. In other words, some of the nicotine might chemically oxidize to one or more nicotine-like compounds with molecular weights very close to nicotine. The nitrogen of interest in a BTB titration is the nitrogen on the pyrollidine ring. The nitrogen on the pyridine ring is much less basic and really doesn't start to protonate until pH levels much below the yellow BTB endpoint are reached. This means that while nicotine actually possesses two basic nitrogens, it behaves with BTB as if it were a mono-base. The tricky point to keep in mind is that while nicotine oxidation products may be formed, these products will likely retain the basic character of their parent compound (nicotine). As a result, you could end up with 90% nicotine and 10% nicotine oxidation products, but a titration would still see it all as nicotine at the beginning concentration due to the fact that the titration is very non-selective, seeing only the pyrollidine nitrogen as relevant to the titration result.
The samples:



The Crock Pot heating up, controlled by a Sous-vide controller (accurate to 1/10 of a degree):



The Titration apparatus:


Vtwin, SeniorBoy, disco180 and 3 others like this.

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Updated 05-18-2014 at 10:03 PM by mikepetro

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Comments

  1. jonhall2's Avatar
    mike, very interested to see your results. will they be published here or do i need to subscribe to the blog?
  2. mikepetro's Avatar
    They will be published in this blog.
  3. mikepetro's Avatar
    Disregard the above tests!

    I discovered a really stupid mistake I made in my first round of testing. I did not look close enough at the Burette I was using. It is a 10ml Burette, and I mistakenly thought that if I emptied the burette completely it had dispensed 10ml. WRONG. There is some space below the 10ml mark, and you have to stop it at the 10ml mark and then refill, or you wont know the true value. During the first round of testing I allowed the burette to empty completely and then I refilled it, counting the first fill as 10ml. Bottom line, the first test I did in my blog is totally invalid!



    I hang my head in shame, but I will post the results upon retesting, using my newly acquired knowledge, and the new burette that WL is sending.[/QUOTE]
  4. jonhall2's Avatar
    mike, thanks so much for doing this testing. i have been on the fence about applying heat to a finished juice containing nicotine from the start of my diy experience. heat helps me marry pg/vg alone a great deal. beyond that, my flavor, nicotine, and pg/vg base are mixed in the bottle and uc cold 24 min. they are typically ready to vape after a 24 hr. steep and continue to get better with time. the oldest diy juice i have is less than 100 days of age. this juice titrates at the same level as the day it was made. simply stored in a dark room temp closet, i will retest at 6 mos. of age.

    no shame in trial and error. i didn't know there was any other way when it comes to vaping. i learned something here today, applaud your efforts, and await new results. thanks again