What happens if I drain out 30 ml of monomer solution while draining out an aqueous layer into a waste beaker?

Answer 1

You are not very specific about the chemicals you are using, and the answer depends on what you want to do next. If you have enough of the monomer left, just dispose of the waste mixture safely. If the monomer quantity is critical, then pour the waste into another separating funnel and run out the bottom layer carefully.