Freebase is the purest type of nicotine and is the most widely used in e-liquids. Ammonia is added to pure nicotine to produce freebase nicotine. This is necessary because nicotine alone will be ineffective to the body; it is composed of negatively charged particles, which basically means that, when it reaches the body, the particles are unable to travel freely through organic membranes.
As a result, in order to make nicotine more usable in the body and improve bioavailability, we must ‘freebase’ it. (The amount of a material ingested by the body is referred to as bioavailability.) Freebase nicotine is present in the vast majority of e-liquids on the market.
Nicotine salts are an alternative source of nicotine used in e-liquids. These are naturally contained in the tobacco leaf, so if you’ve ever smoked a regular cigarette, you’ve already had them! Even at high doses, nic salts can provide a softer, smoother throat hit.