I want to play devil's advocate for a second here. There is no doubt QA and QC is needed in this industry. OTOH hand lets not be ridiculous about it, especially not with "home testing kits" with all the variables they bring especially with "flavoured" liquids.
A large margin of error = a large margin of error. OTOH if the liquid tested in home varies by a few mg either way, that is all that suffice. The onslaught of theses threads proved there were large discrepancies and lack of QC & QA. e.g I bought 60mg and it tested at 42mg, or 100mg that tested at 272mg. I believe these figures as we move on will be things of the past.
In closing, I admire folks seeking safe liquid to vape. OTOH many vapers go overboard with some of their concerns when they never gave a rats behind what cigarettes contained. Vaping is a safer alternative than smoking no holes barred. Is it safe? IMO NO, just safer.
We have been provided a tool to quit smoking while many other methods have failed. The object is to free yourself of the addiction, not continue to be an addict to nicotine under a new form - because if we knew then what we know now, we would have never start smoking in the first place and we wouldn't be having this conversation.