Vapor wrote:

Use dark glass filled with little air space then wrap the bottle or place it in a box so light can never reach it... Toss it in the freezer... Air, light and heat are the enemy... Use several smaller bottles so you they don't need to be tampered with until you are ready to use the contents...

If you REALLY know about the dangers of Nicotine, how to handle it, how to store it, how to protect others from it, order, then pick up some 999, buy some brown 20ml glass bottles with a well fitting seal, use a syringe, then measure 15ml of 999 into each 20ml bottle, seal, then store into a separate sealed container, in the fridge, at a stable temperature below 5C.

15ml of 999, with 135ml of pg, will make 150ml of 100mg/ml nicotine/pg base.

Mix 10ml of that with 40ml of pg, then add 50ml of pg to have 50/50 mix of pg/vg @ 10mg/ml nicotine.
Follow math in ratio to that for higher strength nicotine mg/ml

I use 10 to 12 mg/ml, and flavour,
that is, from a base of 100mg/ml nicotine,
12ml of 100mg/ml base, mixed with 33ml of PG, 5ml of flavouring, then top up with 50 ml of VG.
That makes 100ml of 12mg/ml nicotine, with added flavouring, to my choice, all using Pharmaceutical Grade, 99.8 BP, USP grade PG and VG product.