alien Traveler is correct. pH is an aqueous property, and VG and PG are both more acidic than water. Not by a lot, but some. So in order to be able to use pH to tell salt vs free-base form accurately, there would have to be some additional calculations beyond simple Hendersonn-Hasselbach math to get the pKa of nicotinium (nic-H+) in the base, as opposed to water. I think it could be done, but I've not done it, and I doubt I will.
The other way is to dilute the nic base in water, so that water is the predominant solvent component. Then the nic will be acting closer to how it is in pure water. Not perfect, but better. I did this when I was running titration curves for the Box Elder samples way back when. For 100 mg nic base, I would dilute to about 5% in water, then titrate that and calculate backwards to get to the original nic concentration. The curves inflected where I expected them to at half-eq point (pKa of nicotinium ion), so I assumed the dilution was good enough.
I dipped an alk-acid paper into some 18 mg VT TH, unflavored, this week in the lab, and it came out more blue than green. So pretty alkaline, but the color was not deep, so direct color comparisons with the key on the paper tube was not easy. But I would estimate high 9s, certainly not as green as 8.5. but again, with only 20% water, it is not really a valid experiment. Better to dilute it and analyze the topology of the pH-curve.
The other way is to dilute the nic base in water, so that water is the predominant solvent component. Then the nic will be acting closer to how it is in pure water. Not perfect, but better. I did this when I was running titration curves for the Box Elder samples way back when. For 100 mg nic base, I would dilute to about 5% in water, then titrate that and calculate backwards to get to the original nic concentration. The curves inflected where I expected them to at half-eq point (pKa of nicotinium ion), so I assumed the dilution was good enough.
I dipped an alk-acid paper into some 18 mg VT TH, unflavored, this week in the lab, and it came out more blue than green. So pretty alkaline, but the color was not deep, so direct color comparisons with the key on the paper tube was not easy. But I would estimate high 9s, certainly not as green as 8.5. but again, with only 20% water, it is not really a valid experiment. Better to dilute it and analyze the topology of the pH-curve.