I'll be talking a bit to Kurt about this on my show at 10pm EST:
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Agree. Glad to see Nick's post. It seems we are still "Pilgrims" here in the USA.Excellent post Nick...seems that the evolution of vaping in the UK is advancing a little faster than here in the US of A.....I hope "promising moves are afoot"....Quality Controls in place and Published would better protect the vaping community AND the Companies....
AriM, no need to toss out HCl. What you need is solid anhydrous potassium hydrogen phthalate (KHP) and aqueous 0.01 M NaOH. And an analytical balance (something that all mixing vendors should get...see density thread).
1. Weigh accurately about 0.48 g of KHP. Best to have about 4 samples of this. I weigh to 4 sig figs.
2. Titrate each KHP sample with phenolphthalein indicator to a barely pink end point, with the NaOH(aq). Calculate the molarity of the NaOH(aq). Use a buret. You should be able to get the molarity to 4 places past the decimal within a 1% std deviation. Now the NaOH is standardized.
3. Titration the HCl against the NaOH with phenolphthalein. Do several titrations to increase precision. Calculate the HCl molarity. I shoot for 4 sig figs and about 1% error. Now the HCl is standardized and I can use it for pH curve titrations for nicotine content.
4. Once every few weeks, restandardize the NaOH (its conc will drift due to CO2 absorption), and restandardize the HCl. HCl won't drift like NaOH will, but I do it anyway to be sure.
PM me if you need details about glassware and other questions.
Also, I don't think the vendors actually knew there were problems until there were complaints. Not trying to defend them...I'm with you: when it comes to something a potentially dangerous as nic, I would be very precise and accurate. But the vendors I have dealt with have for the most part been very concerned about getting it right. They simply did not have the chemistry knowledge to know what that meant.
This was illustrated dramatically to me when I published essentially freshman chemistry titration curve results, and people thought I had done magic. If I have done nothing else for this community, at least there is much more chemistry knowledge now. Still a ways to go, but the consciousness has been increased significantly.
Great stuff there Kurt. Does the KHP need to be prepped in a nitrogen environment though? I mean can it absorb enough H2O in free air to become contaminated? I was considering investing in a closed titration system (semi-automated) to try and remove some of the human error, and speed up the process.
How much more consistent do you expect I could get my results with "standardized" HCl?
I am sure they didn't know Kurt, but that is the part that scares me above all else. I don't want to come off as being against anyone or anything, but we are dealing with a drug....that may well have to be treated as such (from a regulatory standpoint) in the very near future. I wish there was a coalition of vendors/mixers here in the USA, where people who don't have the access to information and gear, can get some help. At the very least some form of mandate within the industry, stating that such testing is necessary...and to avoid in house testing is bordering on negligence. I'm no lawyer, but that is the way I think a court of law would view it, should anyone ever become injured (and make claims against a vendor of "e-liquid"). Obviously such cases go after the deepest pockets, but I would hate to see some national (sensationalized) scandal against the vaping industry, just because a few folks were negligent.
I appreciate the information you have given out, as it benefits us all.
No, KHP can generally just sit in a plastic jar without any water absorption. Its the great goto for acid/base standardization, since you get moles accurately from the mass, and its monobasic. Its really the only way I use for this application, and we use it regularly for teaching lab titrations.
More titrations means more data to average over and lower std dev. My goal was to get nic to 4 sig figs. Some vendors have published nic levels of, say, 36.4532 mg/mL, but were using 0.1 M acid. That's only one sig fig, so you really could only report 40 mg/mL. Just because the calculator is telling you lots of places past the decimal does NOT mean you actually know and can support those digits.
I standardize the HCl. Then use a 10.00 mL vol syringe to put 10.00 mL of an unflavored liquid into a 100.00 mL vol flask, and dilute to the meniscus line. Then I pipet 25.00 mL of that into my titration beaker (I use a stir-bar and pH probe), and titrate it with the acid. My acid this last time was 0.07052M standarized. I do three titrations from the 100.00 mL solution, then repeat the whole thing with a new nic-liquid 10.00 mL, which total gives me 6 titrations that I average over. I want <1% relative std dev in the end, and 4 sig figs. The titrations are pH curves and I use a spreadsheet to calculate the inflection point (Max negative slope, at equivalence point). A bit of work, but not bad, and the results are air-tight. That's how I did the original BE samples.