Hello. (I really only have one short question, unless others have very different methods of detecting nicotine un-purity, but I want to explain what and why I need it for thus the long text. Just so you know that you can skip to the last 2 lines in order to read my question, since reading the hole text isn't a strict necessity) Recently I have received nicotine that there is something wrong with, it taste very bitter and it tastes even worse when mixed with flavors(since I vape with 14mg/ml nicotine I think that if I had used less of the 30mg/ml liquid I start of with it might not have been as bad but still it was bad), the taste of it is very similar to the smell of nicotine and I theorised that perhaps for some reason the nicotine in the PG or VG have oxidised far more than it usually have, but the man in my local vape store didn't consider that a possibility. But in any case I am getting closer and closer to have to buy a large amount of 100mg/ml liquid because the European TPD is getting ever closer to be implemented in my country(Sweden), I plan to acquire 2-3 litres at least and then split that up into individual 100ml glass bottles that will be put into my freezer until it is consumed. That way I should have all the nicotine that I will need for the coming years, for as long as the nicotine stays fresh/good. My problem with the TPD isn't just that I hate to have to get hundreds of 10ml bottle to be poured into a large bottle but the TPD restricts the nicotine content to maximum 20mg/ml, which means that it can get hard or difficult or simply unpractical to mix recipes freely and still end up with the 14mg/ml that I require. But having bought nicotine from a few different places I have experienced a large range of quality, and I want to find some way of detecting how pure a nicotine are so that I can best choose from whom to buy 2-3L from. Something like finding a flavor that get altered much by un-pure nicotine bases. Does anyone know of any flavour that gets altered by not entirely pure nicotine bases? The more the flavor changes the better so that I can compare different nicotine sources with one another.