On trimethyl pyrazine ... it comes in a 10% solution and should be used at concentrations no greater than 80ppm.
Lets make it so that each drop is 10ppm in a 10ml solution. That way, 8 drops would be the maximum used and you'd have a lot of room to play.
So ... we want each drop of our final solution to contain ... 10gx10/1,000,000 = .0001 g of Trimethyl Pyrazine.
As it comes, each drop of the 10% solution contains .004 g.
A 6ml container would need to contain a total of .0001 g/drop X 25 drops/ml X 6 ml = .015g
.015g/.004g per drop = 4 drops
So, add 4 drops of this to a 6 ml container, fill it the rest of the way with PG and shake well. Each drop will amount to 10ppm in a 10ml batch of e-
juice, so you can use up to 8 drops.