As far as nicotine bases used to make juices go the nicotine can be based in either PG (Propylene Glycol) or VG (Glycerin, or Glycol) or a mix of both. That's no problem. The rest of juice is mostly mixed with PG, VG or a combination of both. Flavorings and coloring can come mixed in PG, VG, alcohol or rarely: water base. PG based flavors are more common than VG based flavors.
VG is viscous (thick) and is often thinned to improve wicking in atomizers. PG, H2O and alcohol are choices for thinning VG.