CAUTION!
Due to its very high toxicity 1000mg/ml nicotine should only ever be handled by professionals or very experienced people with all the precautions and lab gear. In most if not all countries possessing pure nicotine requires a license.
Even with the more readily available 100mg/ml nicotine (generally mixed with 90% PG) new users should take special precautions and pay close attention to correct dosage. E.g. it only takes 1ml of this solution added to
9ml base to make 10mg/ml concentration and it's easy to accidentally overshoot.
For new users wanting to try DIY I would recommend starting with pre-mixed bases.
For instance when wanting to make 12mg nic 70PG / 30VG base suitable for clearomizers one could
buy:
1) 1x 100ml 36mg PG
2) 1x 100ml (0mg) PG
3) 1x 100ml (0mg) VG
Empty the above in a 300ml+ (air tight and dark glass preferred by some) container and shake.
Add flavouring concentrate as required, steep and start sampling.
It's always a good idea to have a concrete idea of what one wants to achieve and how exactly to get there so always research well and keep good notes.
Good luck.