It is the dose of the toxin and its concentration in terms of LD50 or LC50 which is lethal or fatal to the insects species concerned in accordance with the science of toxicology.

ethyl acetate is a liquid that can be fairly volatile , usually 3 drops of pure ethyl acetate, can kill insects without any soil in an empty vile of 300ml

3 drops equal 0.15 ml of ethyl acetate

which means the volume of your tube is fairly equal to 950ml

10 drops which are equal to 0.5 ml of ethyl acetate

i think the soil will limit the evaporation factor of the liquid

i recomend you add 1ml of ethyl acetate to your vile

preferable you try several volume of ethyl acetate but i think 1 ml will do the job

some insects are very fragile to chemical products and can be deteriorated very easily

especially collembolan species i think there's other ways to kill insects in the soil